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1. Old Style Focus Hartmann Control Warning Reasons max 6 lines The shutter is not enabled Check switch on main HERMES electronics panel SHUTTER WILL NOT OPEN See reasons above The instrument is not healthy Check via HERMES spectrograph engineering interface 4 Spectrograph Engineering Interface Figure 9 1 HERMES Spectrograph Control Window eoo IX Automatic Focus Using Hartmanns Window Auto Focus using Hartmanns CCD CCD 1 Blue CCD 2 Green CCD 3 Red CCD 4 Infrared Processing Progress not started not started not started not started Piston Spectral Spatial Piston Spectral Spena Piston Spectral Spatial Piston Spectral Spatial Current HAW Position 230 4 200 6 NIA 280 1 200 6 290 3 200 3 NIA 320 0 200 6 N A Settings at Image Capture o o o P o e DER Difference in Pixels Difference in Units f Suggestednewsetings J ToO o o 1 T T T T do Is the result in spec A Home Apply Apply Apply Apply Apply Apply Apply Apply Apply Apply Apply Apply Apply Arm Apply Arm Apply Arm Apply Arm all 13 23 3 3 all 1 3 23 38 all 1 3 2 3 38 all 1 3 23 38 all Pixel Shifts 1 3 13 us a TT 213 213 213 213 i o jaa KE 313 313 313 313 Close Stop Data collection script Repeat Figure 9 2 Automatic Focus Window e090 X HERMES Focus
2. Config Plate more Messages i 09 37 45 Network not running am starting it A Y Figure 11 5 The 2dF main window upon start up After initialising the system will show the status as Available in green 69 O O x Confirm Trust in HERMES Positions Do you trust that the current positions of the HERMES mechanisums have not been changed since the software was last run If yes invoke Trust and we will not bother homing them on the next move Don t Trust Figure 11 6 The HERMES Trust Prompt e A subsystem selection menu will appear This allows 2dF to be fully shutdown while leaving the CCD system and PTCS still running which is the normal method of shutdown during a 2dF run If there has been errors with the CCD system or PTCS then these system s should also be selected for shutdown e A number of error messages will pop up as various parts of the system lose commu nication with each other Communication errors can be cleared 2 Once all of the subtasks have exited a small dialogue box will appear asking you to confirm the exit for the main control task e Before accepting this check that a message appears in the tdfct text box shutting down the positioner power supplies If not seek expert assistance e There are several push button options on the right hand side of the window vme systems HermesICS and local system The bu
3. 1537 arXiv astro ph 0607125 shows the effects of this straightening It can have adverse effects on target priorities and so the concerned user will need to experiment with this option to determine the optimal solution Collision Matrix It is occasionally useful to save the matrix of fibre collisions which has been calculated for this field This enables quick restarts of the software later on This file can however be rather large Enforce sky quota This option forces the allocation of the requested number of sky fibres This can result in subtly lower target yields for some fields although the effect is small undetectable for most source distributions accepting that the full sky quota is allocated to skies Most datasets will be of little value with less than 15 sky fibres 20 30 fibres is more typical for most projects Peripheral weighting for Fiducials This gives enhanced weight to selection of stars towards the edge of the field which is typically beneficial for acquisition and prevents all of the fiducial stars being crowded into a small area of the plate as can happen with the SAcon figure algorithm Weight fiducial target pairs For CBS observations one may wish to allocate the fiducial fibres in pairs in order to guide in both positions of the beam switch Setting this flag gives extra weight to paired fiducial allocation Note it is often more efficient in terms of fibre allocation for the user to allocate fiducials by hand b
4. 2dF HERMES Documentation Volume I User Manual Gayandhi De Silva Version 1 0 beta Dated 3 May 2014 Compiled Thu 8 May 2014 o he A Australian Government Department of Industry The Australian Astronomical Observatory WWW aa0 gov au Contents Contents I Overview of 2dF and HERMES 1 2dF Overview II 4 5 1 1 1 2 Basi s oem sisas diria KAN a E Da a end 1 1 1 What is the reconfiguration time 2 22 Cm nn 1 1 2 What is the minimum spacing in arcseconds on the sky of 2dF fibres 1 1 3 A note on exposure time o Chromatic Variation of Distortion e e 1 2 1 The Chromatic Variation in Distortion of the 2dF prime focus corrector 1 2 2 Does the Atmospheric Distortion Corrector ADC work correctly 1 2 3 Chromatic Variation in Distortion CVD 1 2 4 Field distortion Differential plate scale and ZD 1 2 5 Quantitative estimates of the effect oo HERMES Overview 2 1 2 2 2 3 2 4 HERMES Components 2 1 1 Slit Assembly 222222 Connor 2 1 2 Collimator and Beam splitters 2 22 Coon nn nn 2 18 Gratings s s 44 ha sakes a ae eek 2 1 4 Cameras and Detectors m nn nn Resolution and Efficiency m nn Spectrograph Focus 2 22 22 mann nn References cc querra a ER are Calibrations and Overheads 3 1 3 2 Detector Settings oh Calibrations s s e scc pegas 20 5884545
5. 6 Click on Start CCD Run 7 Now you will be given a choice of lamps see Figure See Table for appropriate Flat Lamps and Exposure Times NOTE NEVER mix guartz lamps this will create an illumination that not only varies in intensity across the FoV but also in spectral response and would be useless as a flat field 8 You can click whether to leave the flaps closed after the exposure this is useful if you are doing another calibration frame e g ARC immediately after as no time is wasted opening and closing the flaps NOTE The flat field lamps require a few moments to warm up to their operation temper ature This is of the order of the time reguired for the flats to close However if the flaps are left closed between observations the flat lamps may not reach their intended stable illumination spectrum before the exposure is started 14 3 3 Wavelength Calibration Frames ARCs Wavelength calibration or ARC frames are taken using the lamps in the calibration unit These illuminate the flaps below the corrector There are two Copper Argon CuAr two Iron Argon FeAr lamps two Thorium Xe ThXe lamps a Helium He lamp and a Neon Ne lamp which can be turned on separately or in combination The recommended lamps for HERMES wavelength calibration are the two ThXe lamps While its possible to expose with other lamps they are have not been tested and are currently not supported by 2dfdr The default exposure time is 1
6. These are illustrated in Figure 6 1 Annealing This governs how quickly the annealing routine cools during the allocation process The Standard setting is generally fine Weight close pairs ThetaMin ThetaMax In some circumstances one may wish to give additional weight to closely packed targets at the expense of overall target yield These allow this to be setup but beware of the odd effects it will have on your allocation This option has not been extensively tested to date Cross beam switching Ifthe observation requires Cross Beam Switching CBS between pairs of fibres then the user should first generate the paired target positions using the menu In addition to the directory containing configure the software also looks in the directory given by the CONFIG FILES environment variable 40 option Commands gt Generate CBS pairs and then set the CrossBeamSwitching flag This gives additional weight to targets which are successfully allocated pairs of fibres at the expense of overall target yield Straighten fibres This gives increased weight to allocations which have fewer fibre crossovers While this will have some impact of target yield the effect is small undetectable for most source distributions and results in fields that typically require fewer fibre parks between configurations hence reconfiguration is faster perhaps by 10minutes 20 in some cases Fig 13 of Miszalski Shortridge and Saunders et al MNRAS 2006 371
7. This application is available on aatlxa and can be started from the terminal by typing obsplan This starts the software and opens a window in which all parameters observing plate coordinates and name of a field can be introduced Each observation field is entered in a different row with the possibility of observing it or not by just clicking the left box To compute the observing times just click in the green Apply button and all values will be updated 45 46 Chapter 8 Working with Complex configurations This section covers more detailed information and many users can LU safely skip it Recent years have seen a rise in the number of programs that require complex configuration strategies to maximize the yield of a 2dF observing run This guide is intended to outline some of the strategies that have been adopted in the past It is not exhaustive and we welcome comments and suggestions Large scale survey programs have their own special requirements with regard to target al location priorities The GAMA survey project Driver et al 2009 A amp G 50 12 implemented a very detailed multi year survey strategy which is documented in Robotham et al 2010 PASA 27 76 While this strategy is likely more complex than most program will need many of the issues of concern are discussed This guide is not intended to replace the Configure manual 8 1 The problem 2dF has only 7350 400 fibres once sky fibres and the current
8. lt Ctrl gt D and then quit It may be necessary to start sysgo see XXX 71 72 Chapter 12 Using the Focal Plane Imager The focal plane imager or FPI sits between the field plate and the sky and has cameras both for looking at the sky and for looking at the plate It is used to determine the astrometric calibration used by the 2dF robot to accurately place fibres relative to astronomical objects of interest It can also be used for a myriad of tasks requiring an imager including field acquisition focusing the telescope measuring the seeing and general astronomical imaging The FPI interface consists of three separate windows shown in Figure 12 1 FPI Main Window This is the main control window for the camera FPI SkyCat This is a standard AAO SkyCat window which is tied to the FPI sky camera and updates whenever a new image is taken with the FPI Select Object This window lists the objects in the FLD file corresponding to the currently configured plate in the observing position This window does not come up until requested by clicking Commands Select Object and Poscheck from the menu Normally the FPI is parked out of the field of view otherwise it would obscure the fibres on the plate It can be centred in the field or parked using the controls accessed by clicking on the Control Options button Unless precision tasks such as a poscheck are being undertaken there is no need to have the FPI survey th
9. such that the first half of all fibres are readout with the Left amplifier and the second half of all fibres are readout with the Right amplifier This splits the spectrum in a single fibre Using all four amplifier reads the detector in 4 quadrants Using any two amplifiers gives 1 2 the readout time and four amplifiers gives 1 4 readout times from the values given in Table 3 1 Each CCD can be binned independently in spatial Y and up to 2 X in the spectral X direction for all readout modes The readout times for binned data using two Left amplifiers with FAST readout are as follows X 1 Y 1 71sec X 2 Y 1 52sec X 1 Y 2 36sec X 2 Y 2 26sec All readout modes in all CCDs reach saturation at 65536 adu The level of dark current in the four CCDs is between 1 5 3 0e pixel hour 3 2 Calibrations At minimum each configuration observed with HERMES requires a fibre flat and arc exposure More frequent arcs eg before and after a science frame can be taken for higher precision wave length calibration requirements Fibre flats need to be taken only once for a given configuration provided the slit unit has not been moved For fibre flats there is a selection of quartz lamps installed on the 2dF top end ring The 75W lamps are recommended for HERMES flat exposures The typical exposure times for fibre flats are given in Table 3 2 for both nominal and high res mask mode using 2x 75W Quartz lamps installed on the 2dF top end ring For di
10. 50 DEC 72 21 40 36 21 05 02 FWHM 7 28 pixels 2 2 Arc Seconds Proper Motion AS year None Specified 21 05 02 Centroid is 67698 37845 on field plate 5 1 ae 21 05 02 Using full image for centroid cae plate we UL To 21 05 02 Action MARK Task DSERV completed Is at radius 76972 21 05 05 Centroid is 106 41 101 23 in window 262 41 257 23 on detector Theta 2 44 21 05 05 FWHM 6 88 pixels 2 1 Arc Seconds A 6 21 05 05 Centroid is 67719 37831 on field plate Fiver numbers aus 21 05 05 Action MARK Task DSERV completed Spectrograph Guide Fibre Ki Spect fibre 150 Pos Check progress Lol Select Goto RAIDEC Goto xo Close Record on Standards minuta w 16 1d File Low 1308 High 1418 Auto Set Cut Levels 1 Zizi sizia Figure 12 1 The three windows of the Focal Plane Imager Control 12 1 FPI Imaging Options Continuous Imaging The FPI can be set to contiuouly take images until stopped by ticking the Continous Imaging box before starting an exposure The sequence is stopped with stop repeat Dark Frame A dark frame can be taken by unticking the Open Shutter box Calculating centroids and FWHM If the Calc Centroid box is ticked the software will mea sure a centroid either in the whole field of view or within a centroid box defined by the user The centroid properties are shown in the scrolling message area of the FPICTL window Centroid Bo
11. Control HERMES Spectrograph Focus Mechanisum Control Piston Spectral Current Request Current Request 190 0 200 8 Viahome Move Clear sae H Settings 200 6 Viahome Move Clear ane pe Move All 280 1 290 3 200 2 Viahome Move Clear Load 200 4 4 Viahome Move Clear Settings Close Im 320 0 Figure 9 3 Focus Mech Window 600 IN HERMES Focus was Changed The HERMES Focus settings are different from the saved values for this slit and you have enabled the focus to change appropriatly when the slit changes so these values may be lost Save current settings as the new standard plane kocia an Cancel slit move values for 2dF P1 Figure 9 4 Confirm changes to focus values 55 If the shift was large repeat the script to confirm the movement has been applied correctly This is needed as the proposed correction assumes a linear relationship between pixel shift and focus which is only valid for small focus shifts At the end of the scrip both hartmann shutters will be left open If for some reason the focus script was aborted mid way ensure both Hartmann shutters are opened prior to taking science frames Once you are happy with the focus values select the Focus Mech button from the HERMES Spectrograph Control Window The Focus Mech Windown will open up as shown in Figure 9 3 In here
12. Flat Fields 15 1 Offset Sky Frames To accurately subtract sky it is necessary to calibrate the throughput of the fibres These vary at the 10 level between configurations though they are stable to about 0 5 while tracking 89 on a given configuration This calibration ideally requires a bright flat source unfortunately the flatfield lamps are neither flat or stable enough The default is to use the dark sky Because it is dark the data reduction system bins up along the wavelength axes so as to avoid the need for excessively long exposures There are other options however e For work in the red or the blue if the 45577 line is on the detector throughput calibration using night sky lines gives sky subtraction comparable to that obtained by dark sky flats The 2dfdr data reduction system has an option to use night sky lines for sky subtraction Of course this method will not work at high resolution in the blue where there are generally no sky lines e If done carefully telescope 1 hour from the zenith away from the rising setting sun twi light flats can work better than dark sky flats this is particularly true for high dispersion work in the blue where there are few sky counts in dark conditions even in 5 10 minute exposures If in doubt take both twilight flats and dark sky flats In any case the standard procedure is to take 3 exposures with the telescope offset 10 arcseconds in different random directions from
13. Guide stars and sky regions should be set to 9 Magnitude The magnitude of the object in format mm mm This is used for diagnostic plots within the data reduction software and is not critical to observing Program Id This is an integer uniquely identifying a specific project While the integer value is ignored it should not be omitted in the fld file Proper motion in RA If the PROPER_MOTIONS keyword is listed in the header then this col umn contains the RA proper motion in arcseconds year A proper motion correction is made at the time of configuring immediately before observing for the position of the object If the PROPER MOTIONS is not set then this column should be ommitted Proper motion in DEC Same as above but for declination Comment Any remaining text up to the end of the line is taken as a comment and will be included in the output FITS fibre table Some additional instructions can be included using special keywords in the comment field and are described in the configure manual TO DO Link 5 3 1 Example FLD file A comment about this file Another comment LABEL My favourite field UTDATE 2013 1 1 CENTRE 21 00 00 20 00 00 EGUINOX J2000 PROPER MOTIONS WLEN1 4500 WLEN2 8600 Proper motions in arcsec year Tf no wavelength is assigned here the default wavelength which is set at the time of observation is used All fibres with specific wavelengths will be positioned optimally for that wavelength and
14. Options menu 7 From the Commands menu select Import Allocations and select your imp file This will allocate the fibres as specified in the imp file 8 Now select Lock Allocations 9 You can now proceed with the normal configuration as you did in step 1 above but the locked fibres will stay in place 8 2 2 Creating your imp file The file saved by the File gt List option in Configure a lis file by default is a plain text file which shows which fibres are allocated to which targets The format is close to that of a fld file but with an additional column of and a column of Fibre numbers between the and the Object Names The imp file format is almost identical to that of a standard fld file but with the addition of an extra column of fibre numbers This column should be the very first column i e it goes before the Object Name column of a standard fld file To convert the lis file into a imp file simply delete the first column of characters that have been added Modify the contents of the imp file to only list those fibres needing to be locked or else all 400 fibres will stay locked For some programs it may be possible to edit the imp file by hand in a text editor For most programs you will probably want to write a simple script to remove or re prioritize allocations based on the results of an initial examination of the spectra from a first observation 8 3 2dF set fibre state tool From time to time
15. are introduced The user should examine the configuration at step 5 below to ensure a sensible fibre distribution is being used 4 Insert 30 50 guide stars and 50 100 blank sky positions 5 Configure and inspect the configuration 6 Observe the field 7 Examine the spectra determine redshifts measure radial velocities classify objects etc 8 Update the master catalogue to reflect these observations A safer approach is often to create a second catalogue of new target priorities The processing script would then draw targets for subsequent configurations from the master file but the priorities of classified targets are adjusted based on the information you have entered into the new target pri orities catalogue For example Set the priority of objects with satisfactory spectra to the lowest value Pri 1 Remove objects of the wrong spectral type Flag objects with promising spectra but which will need higher signal to noise Note you clearly cannot make the new target priorities until you have some data and since one needs to have a number of fld files ready in advance of each nights observing this process is most efficient if any given region can be broken down into a number of independent non overlapping pointing centres each night 9 Note that there is no underlying reason why the field centre need be identical to that previously used 10 Repeat steps 5 9 until the required target completeness is achieved 8 2 Loc
16. corrector lenses produces a 195 mm diameter parallel beam Three large dichroic beam splitters separate the beam into the four HERMES channels The beam splitters that define the wavelengths for the four channels are as follows 370 492nm BLUE 560 593nm GREEN 643 679nm RED 754 1000nm TR 2 1 3 Gratings HERMES uses four Volume Phase Holographic VPH gratings one in each channel Two of the four gratings require a mosaic of two gratings on one substrate due to the aperture and line frequency required The HERMES BLUE and GREEN channels use single exposure gratings while the HERMES RED and IR channels use mosaic gratings The central wavelengths of the gratings are Blue 483 3nm Green 578 8nm Red 664 2nm IR 777 8nm The actual angle of incidence within the assembled spectrograph is within 0 1 degrees of the nominal value of 67 2 degrees 2 1 4 Cameras and Detectors Each HERMES channel has four F 1 7 cameras respectively optimized in the Blue 370 550 nm Green 500 650 nm Red amp IR 600 1000 nm Four independent shutter systems allows the four channels to have individual exposure times Each camera feeds one 4096 spectral direction x 4112 spatial direction 15 um pixel Charge Coupled Device CCD from the E2V CCD231 84 family The BLUE and GREEN detectors are both 16 micron standard silicon devices with broadband and mid band coatings The RED detector is a 40 micron
17. help from AAO staff before proceeding The main rules for starting the 2dF control system are to make sure the software is in a tidy state and to start the control systems before applying power to anything The startup procedure depends on exactly how the system was shutdown see Section 11 3 NOTE tdfct cannot be run over the network e g via ssh Remote observing depends on a VNC connection to the observing console at the AAT This is the step by step guide to starting 2dF HERMES from scratch 1 Before starting determine what state the system is in and why tfct has not already been started Ask the technicians 2 At the console for aatxdb in the control room select aatlxy from the system chooser and login as aatinst The password is known by AAT staff 66 Figure 11 3 The ARC lamp selection window 67 800 Ccd Lamps Please Select the LAMPS to used for the FLAT 75W Hermes 75W AAOmega 20W sow 4 Select to leave flaps closed after Flat Field _Go Cancel Figure 11 4 The Flat field lamp selection Window Type cleanup into the xterm to make sure nothing has been left running Type hermes into the aatlxy terminal window to get the 2dF HERMES control system running The 2dF main window will appear see Fig 11 5 To initialise all of the hardware choose the Initialise item from the Commands menu During the initialisation of the HERMES system a prompt asking to confirm trus
18. indicates the exposure time and status and during readout a light blue bar indicated the progress of the readout time The next panel indicates the next or current run number A series of buttons under Select Observations determine the observation type The selected observation type is written in the header of the generated files They are Object Take a regular science frame of the target s Dark Take a dark frame Bias Take a zero length frame Offset Sky Used for an offset sky frame for sky subtraction and or throughput calibration Offset Flat This is used for twilight flat fields it might also be used for a dome flat but make sure to keep a log Detector Flat This is used for flat fielding the detector response Selecting this will move the slit to illuminate the entire detector Fibre Flat This is the standard flat field These files are used in the data reduction to find fibre tramlines spectra across the detector and also to take out variations in response 63 2dF HERMES cep control dialog Ctrl C CCD Telem 170 0K Heater5 0V CCD Telem 170 0K Heater 5 0V CCD Telem 170 0K Heater 5 0 CCD Telem 170 0K Heater 5 0V idle idle idle Next Run 5 Next Aa 5 Select Observation RunType SS Sky Sub Mode Object 1 BL 18 0 None Normal 2 GN 18 0 Beam Switch Bias Dummy 3 RD 18 0 Cross Beam Offset Sky Glance 4 IR 18 0 Shufe Mini Shuffle Offset
19. it can be desirable to temporarily deactivate specific fibres for the 2dF positioner The most common reason for this is to set up a field for Nod and Shuffle observations where a number of fibres need to be disabled in addition to those that are un available due to damage The temporary removal of fibres with poor characteristics e g fringing fibres is also possible To facilitate the temporary disabling of fibres a utility program has been packaged with Configure from v7 7 onwards The routine set fibre state can be found in the base directory of the Configure distribution The utility should be set to be locally executable Running the script will then provide an introduction to its usage Under LINUX this looks like 50 LINUX gt chmod x set fibre state LINUX gt setN fibrel state Insufficient arguments 2dF set fibre state program Usage setN fibrel state setN fibrel state setN fibrel state setN fibrel state lt tdFconstants400 lt tdFconstants400 lt tdFconstants400 lt tdFconstants400 sds gt shuf Ol1 both sds gt file Ol1 lt file gt sds gt file both lt filei gt lt file2 gt sds gt restore lt file gt In the syntax above the arguments in lt gt are user supplied input files There are three basic modes of operation shuffle file with two syntax options and re store Shuffle will create a new file for tdFconstants400 sds file with the fibres on one or both plates correctly disabled for nod an
20. not it may be necessary to acguire with the FPI as described in 12 3 Once the Night Assistant confirms that the telescope is guiding start the science frames Finally do not forget to start the positioner configuring the next plate 14 3 Taking Data 14 3 1 Typical Observing Sequence 1 FLAT For identifying fibres on the CCD and tram line fitting 2 ARC For wavelength calibration NOTE You can take a seeing measure with the FPI while CCDs are reading out OBJECT frames These should be split up into at least 3 separate exposures so that cosmic rays can be removed by reduction software 86 The coud room is not thermally stable particularly if the room was accessed during the day and so it is wise to intersperse ones observations with flats and arcs if high precision observations are required at the 0 5 pixel level there should be little change over 1 2 hours 14 3 2 Multi Fibre Flat Fields FLATs Multi Fibre Flat Fields are taken using the quartz lamp in the calibration unit The default is the 75W lamp with exposure times BL 18s GN 5s RD 2s IR 3s in the nominal resolution mode Using the high resolution slit mask the default exposure times are BL 40s GN 10s RD 5s IR 5s Set up is as follows 1 Check that the Night Assistant is not guiding 2 Select Fibre Flat run type 3 Set your exposure time for each channel 4 Select type of run Normal Dummy Glance 5 Select readout speed
21. now 18 Field distortion 0 2 3h 20d Oh rotn 11 arcsec 2h rotn O 3h rotn 11 2x10 2x10 0 2x10 365 stars lt ds gt 131 51 123 mas Error arcsec 0 0 2 0 4 0 6 0 8 1 Radius degrees One can improve the above plot by configuring not for HA 0 and then letting the field set for three hours but rather by configuring for some predefined mid point which minimizes the errors in apparent position throughout the exposure In the plot to the left the field has been configured for HA 2 but if one was to start ob serving at HA 0 and observe until HA 3 the maximum error would still be below 0 5arcsec for the full field Note that this field is at Dec 20degrees The situation will be a little different for fields at higher Zenith Distance 19 Field distortion m3 0 2 3h 20d T T T T 3h rotn 5 arcsec Oh rotn 11 2h rotn 0 A Witten It 2 10 3h rotn 11 x a 2x10 2x10 0 2x10 365 stars lt ds gt 162 9B 161 172 mas e ao o a ET 0 0 2 0 4 0 0 8 1 Radius degrees Error arcsec ja o Once one realises that it is possible to observe over the range HA 0 to 3 hours then the next question is is there a correct fibre placement which would allow observation from HA 3 to HA 3 Traditionally one may have used the mid point of the configuration at HA 0 However one global time will not be suitable for each fibre While the HA
22. software may decide that it should check its index marks anyway and use a normal slew to correct its position 81 For normal observing the use of the ADC should be almost transparent with the ADC slewing with the telescope each time the observing field is changed through the night The use of the ADC becomes more important however when observing standard stars In particular after pointing the telescope to the position of the standard star the ADC will use a normal slew to update the ADC position The next stage of a standard star acquisition is to offset the telescope by up to a degree to position a star down the chosen guide fibre at this point the ADC should correct its position using a quick mode slew taking only a few seconds During the final stage where the telescope is moved to offset the standard star from the guide fibre to a spectroscopic fibre the ADC should not be moved as it will affect the position of the standard star Normally the offset at this stage will be small less than 5 arcmin and the ADC will not shift position If you are using a large offset it is possible to simply stop the ADC using the stop ADC button on the ADC sub window before making the offset this makes no difference for the short duration of a standard star exposure When parking the telescope during or at the end of the night the ADC can behave in one of two ways If the telescope is parked from the night assistants console the ADC will keep t
23. the observed fits files have a WLEN field in the fibre information table that indicates the actual wavelength the object was configured for 36 Name 347 187448 354 188889 349 186707 353 190083 351 189626 B 20 21 20 21 20 Ascention mm 59 02 56 02 58 ss 20 304 30 15 04 41 sss 893 735 107 132 Declination dd mm ss sss 20 39 41 425 19 15 45 385 20 14 04 764 19 30 55 424 19 49 03 594 P P 9 9 Pul 9 P_w2 9 P1 37 mag 13 8 13 0 11 6 13 6 12 2 Prog Proper Motion ID 0 0 0 0 0 ra 0 0073 0 0344 0 0017 0 0261 0 0124 dec 0 0150 0 0339 0 0004 0 0252 0 0262 Comments A nice star A nicer star feat at 45004 Calcium Triplet Random galaxy 38 Chapter 6 Using Configure 6 1 Installing Configure The latest version of configure can be downloaded from the AAO s ftp site The same version is used for AAOmega HERMES 2dF 6dF and Ozpoz The current version of Configure imple ments a Simulated Annealing SA algorithm The advantages of SA are explored thoroughly in Miszalski Shortridge and Saunders et al MNRAS 2006 371 1537 arXiv astro ph 0607125 and are summarized in an article in the February 2006 AAO Newsletter In short SA provides 1 Increased yields for complex fields 2 Optimal target priority weighting 3 Highly uniform and guantified sampling behaviour 4 High completeness for fibre pai
24. the plots that follow we will use 0 5 arcsec as the maximum tolerable positional error due to atmospheric effects and aim for a mean error below 0 2 arcsec The concerned reader should review the effects of placement errors in more detail see Newman P R 2002 PASP 114 918 When considering these effects one must also remember that other sources of error including the intrinsic accuracy of the positioner tracking errors the effects of CVD and errors in the input positions are likely to contribute at the 0 25 arcsec level Note when a fibre is away from its target by 1 arcsec one is losing 50 of the available light and the relative losses are greatest in good seeing 16 Field distortion 0 2h 20d rotn O arcsec 2x10 e Ey te TH Tan m x x ee me x x Kant r a he Hy x x wu 5 EN A e Pa pr ee de Hu we 14 gt Na na na me me Ne Be x a a x o o as 2x10 0 2x10 Error arcsec ate ou ou 0 4 0 6 0 8 1 Radius degrees o o x w Here we see the effect of observing a field 2 hours away from its configuration time The fibres in this Dec 20deg field were positioned correctly for the field as it would be observed as it transits the meridian The Zenith distance during transit for this field would be of the order 10deg Two hours later the apparent position of the target objects has moved due to differential atm
25. 0 and an option of higher resolution with a slit mask at R 45 000 at the cost of approximately 50 light loss With the AAT 2dF system HERMES provides high resolution multi object capability for up to 392 objects In its current fixed grating setup HERMES provides simultaneous observations in the following wavelength regions BLUE 471 5 490 0nm GREEN 564 9 587 3nm RED 647 8 673 7nm IR 758 5 788 7 nm 2 1 HERMES Components 2 1 1 Slit Assembly The HERMES receives light from the 2dF positioning system The spectrograph slit assembly holds two interchangeable slit units It provides accurate and stable interfaces for the two fiber feeds coming from 2dF each containing 400 fibres regrouped in 40 slitlets Each of the 2 x 40 V grooved channels in the slit bodies houses a lens relay that changes the F 3 16 focal ratio 21 output of the fibres to feed the collimator at F 6 32 To optimize image quality the slit is curved convex and spherical with a radius of curvature of 935 9 mm For high spectral resolution a slit mask can be inserted manually on a kinematical mount Installation of the slit mask is a day time operations task and the slit mask cannot be exchanged during night time observations The slit assembly also holds a back illumination system used to position precisely the fibres on the sky target positions 2 1 2 Collimator and Beam splitters Post slit a F 6 3 9 3 degree off axis collimator with two spherical
26. 3 A differential change in the plate scale Not correctable The first and second effects are accounted for during observations However the differen tial plate scale change which contains the remaining complexity of the true distortion in this overview would require a mechanism that could stretch the solid metal field plates The Configure software and the 2dF positioner know about these effects and so fibres can be correctly configured for a particular HA but as one moves away from this HA the fibre placements become increasingly incorrect 2dF was designed with a 1 hour reconfiguration po sitioning time so that observations would only need to be performed 30mins from the correct HA In practice most users find 1 hour is acceptable for a full 2degree field configuration and 2 hours is fine for fields near the zenith Smaller fields of view are affected to a lesser degree fields at higher HA are affected more quickly due to the larger differential plate scale change encountered 1 2 5 Quantitative estimates of the effect A series of configurations have been prepared using Configure to demonstrate the effect and are presented below These configurations show the effective positional error note this is not 2dF robot error but rather an an unavoidable effect of differential atmospheric phenomena for a 2dF configuration which has been configured for a certain time and is subsequently observed at a different time In
27. 3hour observation results in a complex arrangement of shifts it is possible to configure the field so as to minimise the overall error for fibre placements over the full 6 hour integration provided plate rotation corrections are applied during observations at least for this Dec 20 degree field The correct procedure is to configure NOT for the some global mid point but rather to position each fibre at some exposure time weighted mid point of the range of its individual X and Y plate positions The complex plot to the left demonstrates this goal The fibres are positioned at the black crosses while the magenta blue green and red arrows indicate the effective positional errors of the fibres during a 6 hour observation between HA 3 and HA 3 for the Dec 20 field The configure software was updated in 2008 to calculate the optimum centroids for all targets given the start time and duration of an exposure The overall loss of signal is minimised as a result of this change 20 Chapter 2 HERMES Overview Blue Camera Red Camera IR Camera AS i ESSA A i Figure 2 1 CAD image of the assembled space frame and the optical layout of the HERMES spectrograph The High Efficiency and Resolution Multi Element Spectrograph HERMES is a four chan nel spectrograph housed in a clean temperature controlled room located inside the AAT west coud laboratory HERMES provides a nominal spectral resolution of R 28 00
28. 80sec in all channels with both lamps in nominal resolution mode and 300sec in all channels when using the high resolution mask mode 1 Ask the Night Assistant to stop guiding 2 Select Arc run type 3 Ensure the exposure time is as required 87 4 Select type of run Normal Dummy Glance 5 Click on Start CCD Run 6 Choose arc lamps see Table for appropriate time combinations depending on the grating used and select whether or not to leave flaps closed after exposure 14 3 4 Object Frames 1 Select object run type 2 Set the exposure time 3 Choose type of run Normal Dummy Glance 4 Click in count and set for number of repeat exposures typically 3 5 Check the type of offset observations None Beam switch Cross beam switch or Shuffle This will typically be set to None 6 When you are happy with your configuration click in Start CCD Run 88 Chapter 15 Additional Science Calibrations 15 0 5 BIAS frames A BIAS frame is taken by setting the run type to Bias Run record option to Run Type Normal Dummy or Glance and then clicking on the Start CCD Run button It is generally a good idea to take a number of bias frames which can be combined to minimize the effect of readout noise To take a set of 30 bias frames which is the recommended number of bias frames select the Count mode and set the count value before starting the observation Bias frames are used by the 2dfdr data reduction software i
29. D is a limitation of the design of the 2dF corrector which was a cutting edge design for its time The practical impact of CVD is an effect similar to atmospheric dispersion but indepen dent of the atmosphere or Zenith Distance Like atmospheric dispersion CVD is a differential refraction with respect to wavelength effect but whereas the atmospheric component is al most constant across the field and so can be largely corrected by prismatic optical elements the ADC CVD varies strongly across the field in a radial direction and with a radial magni tude dependence and cannot be corrected in the context of the current 2dF optics The problem is that the Point Spread Function PSF of the prime focus corrector is strongly chromatic and strongly plate position dependent The effective centre of the PSF in terms of its light weighted position is NOT a constant as a function of wavelength due to the limits of optical design for spherical optics the size of those on 2dF at the time of its construction This means that the correct position on the field plate at which a fibre should be placed to accept the light from a given target is NOT constant with wavelength The Configure software has a detailed model for the 2dF corrector and knows where to place fibres to account for this effect but the user must determine the optimum wavelength to use when placing a fibre Note that in recent versions of Configure it is possible to specify up to 9 differe
30. EG area nahe Preparing for observing In advance of your observing run Preparing field description files FLDs for Configure 5 1 5 2 5 3 General Guidelines for FLD Files Guide Stars Borat sus st eek mu Sex ep ae eee Bp ee Bs ET ED E de che RES Sy Se ms we ae ch ee wt G 11 13 13 13 13 13 14 14 14 14 15 16 21 a a 22 22 22 22 23 23 25 25 26 29 5 3 1 Example FLD file ahaaa aaa 6 Using Configure 6 1 InstallingCONBSULE 2 4 lr sau US e RA Se A eee E ai 6 2 Running Configure on nn 6 2 1 Updating the 2dF Distortion Model 6 2 2 Starting the Software oo 6 2 3 Allocation Options 2 2 posi e ran nan ea 6 2 4 Additional Expert allocation options 2 22 nn nn nn 6 3 What is needed for observing 2 2 nn nn 7 Planning 2dF observing with obsplan 8 Working with Complex configurations 8 1 The problem 2 on nn 8 1 1 Examples sc u Au ann foe ae RODES E ee a es 8 2 Locking allocations for repeat observing 2 2 2 oo 8 2 1 The procedure for creating and using an import file 8 2 2 Creating your imp file 2 2 2 on nn 8 3 2dF set fibre state tool 9 Preparing the instrument 9 1 Focusing HERMES III Observing with 2dF HERMES 10 Outline of observing 10 1 During the Afternoon 10 2 At the start of the first nieht 24 u E arara Heh 44a 4d be PEE A 10 3 At the start of every night o cce sr
31. Fiat_ Offset Details Detector Flat ERREI Fixed Offset Mode Arc je RA fi 0 Flux Cal Dec po A A Select CCDs Repeat Mode Options CCD 1 Blue a cope iGreen gm reine CCD 3 Red Continous Seeing CCD 4 Infrare Count Copy last data file More options name to clipboard Select CCD jo 4 Plot Fibre Errors Start CCD Run Scripts amp hermes focus data acg Cont Script 30f5 Rewind HARTMANN Skip Back Skip Fwd Figure 11 1 The CCD Control Window 64 with wavelength The lamp to use is selected after the Start CCD Run button has been pressed See Figure 11 4 Arc The standard wavelength calibration frame The lamp to use is selected after the Start CCD Run button has been pressed See Figure 11 3 Flux Cal This identifies the frame as having a flux standard in it The software will ask you to identify which fibre the flux standard is illuminating Next the type of run needs to be selected Normal A normal run is taken These data are archived and stored in the regular data direc tories Dummy These data are written to a separate dummy directory and are not archived Glance In this case the CCD readout is displayed on screen but not saved The exposure time is set in the next box A separate exposure time for each camera can be set BL is for the Blue camera GN for the Green camera RD for the RED and IR for the Infra red camera For some
32. Fibre status information Once you have downloaded these files copy them into the configure directory before starting configure as described in the next section NOTE Even if you do use the most current fibre and astrometric information you will still have to tweak your fields at the telescope since things can and do change on very short notice This is especially true at the start of your run 6 2 2 Starting the Software Starting configure just requires running the appropriate executable either from the terminal or if on Mac OS by double clicking the executable in the Finder Remember that unless you have added it to your path you will need to provide the full path to the executable For the standard version with Simulated Annealing gt gt cd configure 7 18 Linux gt gt configure For the original version with the Oxford algorithn gt gt cd configure 7 18 Linux gt gt configureTrad In the window that appears select the appropriate instrument The full configure interface will then come up including the main window quick sequence window and allocation display To get started follow the steps in the quick sequence window Allocation typically takes a few minutes on a modern laptop If allocation takes significantly longer there may be too many targets in the input FLD file See Chapter 8 for more guidance 6 2 3 Allocation Options There are a number of options available within the Configure algorithm
33. XXX Get the local staff to make sure the telescope Z gear is not at its limit if it is this will affect pointing calibration 10 2 At the start of the first night This section is for advanced users only If you have not done this before seek help from AAO staff before proceeding Poscheck etc 10 3 At the start of every night 1 Telescope Focus Once it is dark a star is centered in the Focal Plane Imager FPI see Section 12 3 to focus the telescope described in Section 12 4 10 4 Science Observing 1 Setting up a Field Once the pointing and astrometric calibrations are done these are performed the first night 2dF is back to the telescope see Sections and a field can be set up for the calibrated plate See Section 14 1 for details about how to configure a field with 2dF 2 Field Acguisition see Section 14 2 Slew to the configured field The guide stars are located first on the Focal Plane Imager FPI and then in the guide fibres 3 Calibration Frames see Section 14 3 Calibration frames which reguire the fibres to be set up fibre flat fields arcs should be taken at this point 4 Guiding The Night Assistant should now start guiding on the field Autoguiding is available although a rotation solution is not automatically implemented and so the night assistant may need to tweak things up 5 Taking Data see Section 14 3 Data frames on the target field and related calibrations such as off
34. atic The ADC will be slewed with the telescope but will then be left at the fixed position not generally a very useful option ADC Ignore The ADC will not be moved When slewing the telescope to a new position from the tdfct user interface the ADC track button on the telescope control sub window should be illuminated the default on startup In this mode the ADC will automatically follow the telescope when the slew is initiated The ADC mimic shows a black line at the parallactic angle and the two dispersion vectors The orientation of the mimic is such that north is at the top going clockwise through east south and west just like a compass The parallactic angle will point towards the zenith so for a field in the south west the parallactic angle should indicate the north east and the dispersion vectors should be symmetric about the parallactic angle If the telescope is moved say from the Night Assistant s console the ADC will attempt to follow the telescope in one of two modes for large changes of telescope position greater than 5 degrees the ADC will correct its position in normal slew mode going to its new position via its index marks this may take a few minutes For short moves greater than a few arcminutes but less than 5 degrees it will attempt to correct its position using a slew in quick mode where it slews to a new position without going via its index marks Note however that after several 6 quick slews the ADC
35. ce fibre Because the FPI movement is very accurate large offsets are possible in theory it should be possible to centre an object above any fibre on the plate with a high degree of confidence and accuracy However this also reguires that the APOFF is correct for the plate used If there are any guestions consider testing the seguence on a guide fibre to confirm accurate acguisition The APOFF could be re calibrated if needed as part of this seguence A strong working understanding of the 2dF system and APPOFFS will help greatly 1 Have the night assistant slew the telescope to the coordinates of the target to be observed 2 Select an allocated fibre on the observing plate using the Select Object window of the FPI Camera Fibres nearer to the centre will be easier to acguire Fibres up to 1 2rd of the plate radius are routinely acguired without difficulty 78 3 Note the position of the fibre on the plate in microns as given in the Select Object window 4 Survey the plate and centre the FPI gantry The survey ensures that the FPI is positioned accurately above the plate 5 Take an image and identify the object to be acquired Centre the telescope on the object Take a sufficiently deep image with the FPI to identify surrounding objects which will make confirmation that the offset later has acquired the correct target and not a random star which happened to be nearby 6 Divide the micron positions of the desired fibre by 65 micron
36. d shuffle observing whereas the file option allows the user to selectively disable fibres In all cases the script should be run on the tdFconstants400 sds file found in the path configure V V data_files directory Doing this away from the telescope requires installing the latest tdFconstants400 sds file The current tdFconstants400 sds file can be found through the main configure page The code will create a back up of the old constants file tdFconstants400 sds bck and a restore file tdFconstants changes txt which can be used with the restoreoption to reverse the changes made to the tdFconstants400 sds file Note for configure 7 9 1 onwards The mapping of fibres in 2dF is not always 1 to 1 with the fibre slit position From v7 9 1 onwards set fibre state requires access to the spec_fibres txt file which is available from the support astronomer in order to achieve this mapping The fibre ordering is currently a 1 to 1 mapping 51 52 Chapter 9 Preparing the instrument 9 1 Focusing HERMES The HERMES focus procedure uses pairs of Hartmann shutter arc frames to derive the focus values pair of arc frames are observed each with an occulting shutter closed across half of the collimator mirror left and right half in turn When the system is in focus the obstruction in the beam will merely result in a loss of system throughput However if the system is not correctly focused the two frames will project arc lines onto slightly di
37. d that absolute flux calibration with 2dF is only good to 20 at best The main limitation is the fibre size 2 arcsec compared to typical AAT seeing 1 5 arcsec which means you never get all of the light down the fibre as well the blind offsetting to the spectroscopic fibre never works perfectly It is usually preferable to use guide fibre 200 and a fibre in the 200 300 range as these fibres appear near the centre of the fibre slit Note that for radial velocity standards one might consider using fibres in the center and at either end of the AAOmega slit in order to assess the effects of PSF variations along the slit Note that fibres around fibre 100 appear about 1 4 of the way up the CCD display and fibres around guide fibre 300 appear about 3 4 of the way up Do check that the star appears where you expect to see it Time Saving Strategy standard stars are usually bright enough to be done in twilight A quicker way is to include standards in your science observations if possible or to hit many standards simultaneously e g in a star cluster or other photometric standard fields such as the SAAO E regions in a special configuration This last option has the advantage that you get calibration down several fibres and can check for consistency for optimists or the level of disagreement for pessimists 92 Part IV Data Reduction using 2dfdr
38. deep depletion device with fringe suppression and an ER1 coating The IR detector is a 100 micron bulk silicon device with fringe suppression and a Multi 9 coating The detectors are housed in cryostats operating at about 170 K Each detector is controlled with an AAO2 CCD controller These controllers are configured for operation with the E2V CCD detectors to permit readout from one two or four detector outputs at various readout rates with windowing and binning options 2 2 Resolution and Efficiency Spectral resolution across the detector ranges from 25 000 30 000 for the 4 pixel sampling of the 2 arcsecond slit width the averaged projection over a circular fibre reduces the projected 5 pixel sampling to an effective 4 pixels Spectral coverage is A 25 around the 4 central wavelengths Ac set by the VPH gratings A slit mask can be inserted to get the same wavelength coverage with a higher 2 pixel spectral resolution from 40 000 55 000 at the cost of 50 light loss The beam splitters gratings and cameras coatings are optimized for their respective spectral ranges The HERMES system provides approximately 10 total efficiency from the telescope to the detector signal such that a 1 hour integration time results in a signal to noise ratio of 100 per resolution element for a 14th mag star 22 The currently available beam splitters and gratings have been optimized for the Galactic Archaeology Survey case Alternatives might be pu
39. dvance of your observing run 1 Contact your support astronomer see the AAT Schedule Make sure you discuss with them e What your program is and your observing strategy including exposure times e Recent performance of the instrument e g how fast will field reconfiguration time be for 2dF are the required modes available e Any questions you have about observation description files which must be prepared in advance e g FLD files finder charts observing scripts etc e Which particular mode setup you plan to use for your program e When you will be arriving at the telescope or remote observing site 2 Fill out your AAO visitors travel form regardless of whether you will be observing remotely or at the AAT This allows the AAO to make appropriate reservations etc 3 Read this documentation especially Parts II Preparing for observing and III Observing with 2dF HERMES Users of 2dF must be prepared to use configure at the telescope 4 You should plan to arrive early preferably the day before your first night on the telescope especially if this will be your first observing run with this particular instrument telescope This will give you time to discuss your program with your support astronomer in detail familiarise yourself with the data reduction software and the computing and observing system at the telescope or remote observing site 5 If observing with 2dF prepare your FLD configuration files If observin
40. e plate More usefully a list of the objects in the configured field can be accessed by choosing Com mands Select Object and Poscheck from the menu This brings up the Select Object window The left side of this window lists the objects matching the current filter The current filter is set using the tick boxes on the right side of the window Below the filter options is information on the currently selected object not necessarily where the FPI currently is At the bottom are buttons which can be used to control the FPI Usually the most useful objects are the guide stars which can be filtered using the fiducial target filter Guide stars typically have good magnitudes for FPI tasks like focusing the telescope and checking the seeing Once an object is selected use the Goto RA DEC button to move the FPI into the field and centre it on the selected object Images can be taken by setting the options in the FPI Main Window Guide stars magnitude 12 14 typically require exposure times of 1 4 seconds for good images Particularly for focus and seeing measures exposures of at least 1 2 seconds are necessary to get stable measurements of the seeing SNAFU stars are too bright for such checks When 2dfdr is first started this window is minimised 73 E Focal Plane Imager 2x E Object selection dialog Sel Field i
41. e using your personal computer make sure you know how to access files in the appropriate directories on the AAT computer system e 3 Prepare all observing files if the astrometric solution is available a All 2dF field description files FLDs must be allocated to binary sds files using configure for loading onto the telescope Because the parameter files change for each observing run These should be prepared using the version of configure on the AAT computer system or at least with the most recent version of the 2dF parameter files b Copy the final sds files to the working directory for the night 4 Ask for the instrument telescope to be released before using the observation interface 5 Configure the first fields on 2dF 6 Take dark or bias calibrations as needed 1The astrometric solution is typically updated each time 2dF is re installed on the telescope sometimes more often This process is called poscheck 8 59 7 After 4 pm and after checking with the afternoon technician the dome lights can be put out Check that there are no lights left on in the dome Note that the visitor gallery lights are on a timer and switch off automatically a few minutes after the main lights are a out Check the top in particular as the diagnostic LEDs are occasionally left on o ao a o Take fibre flats and arc exposures to confirm exposure times d Focus the spectrograph 8
42. ection and the spectroscopic fibre from the select object pivot section 4 Now enter the RA and Dec of your standard star in J2000 coordinates these are the only numbers you have to enter manually and press the calculate button Three sets of corrected offsets are displayed in red The first is the offset in arcsec from the centre of the field plate to the guide fibre The second is the offset in arcsec from the guide fibre to the spectroscopic fibre The third not often used is the offset from the centre of the field plate to the spectroscopic fibre Note that the corrected offsets already allow for cos dec and other tangent plate corrections 77 5 series of buttons is now activated at the button of the window The first is Slew to object The user should click this while the Control telescope switch is activated a yellow gray toggle button just above the Slew button This should slew the telescope to center the current field plate on the star The next button down the standard star sequence should now be active 6 Unpark and centre the FPI a survey in not usually required here Centre the standard star on the FPI Move the FPI clear and wait for the telescope axis to revert to A B from the FPI reference axis 7 Once the axis is set click the Offset star to fiducial button the next element of the standard star button sequence at the bottom of the standard star control This drives the telescope to place the sta
43. f available but are not required to reduce the data since 2dfdr can also do bias subtraction using the chip overscan region this latter option is the default and is usually adequate IMPORTANT Note that the dome should be dark when taking BIAS frames as the coud room is not absolutely light tight To avoid problems close the dark flaps located in front of the CCDs of AAOmega 15 0 6 DARK frames To take a DARK frame set the exposure time which should be similar to that of the scientific observations and specify Dark Run and Normal Run and then click on the Start CCD Run button As with biases it is advisable to take a number of darks using the Count option so that they can be combined to remove cosmic rays Again these are used by 2dfdr if available but are not required for data reduction IMPORTANT Note that the dome should be dark when taking DARK frames as the Coud room is not absolutely light tight To avoid problems close the dark flaps located in front of the CCDs of AAOmega 15 0 7 Long Slit Flat Fields Long slit flat fields can be taken using AAOmega by defocusing the spectrograph by 3000 um in piston before taking a Flat Field lamp exposure Once the focus of the cameras has been moved see Sect and Figure select L Slit Flat run type and take an image as explained in the previous subsection DO NOT FORGET to return the position of the spectrograph to the correct focus values once you have taken your Long Slit
44. f the 2dFSys will appear first while the pop up window indi cating the resetting of 2dFPos may need some time a couple of minutes even a bit more sometimes 3 After a clean 2dF shutdown a CCD reset is NOT required The CCD system only needs resetting if the VME system was Cleaned up during shutdown or if there have been CCD problems If you need to do this follow these steps a b There are two VME systems that control the HERMES CCDS The names of these will be noted on the control room white board One system aatvme6 VxWorks aatvme10 Solaris is in the control room behind the blue screen The system is at shoulder height next to the network switch cabinet Find the relevant reset switch It s a big red button at the bottom of aatvme10 but only a small black lever switch for aatvme15 Both are clearly labelled with RESET Press flip this once to reset the CCD system The other system aatvme17 VxWorks aatvme16 Solaris is located next to the HERMES room in West coude area This cannot be reset manually You need to telnet into aatvme16 machine by typing telnet aatvme16 Login as hermes and ask the technical staff for the password Once logged in at the command prompt type vmeReset 4 Finally follow the steps included in Section 11 2 to initialise 2dF starting from item 2 1Tf the boot messages don t appear then telnet 2dfpos and look for gt which is the VXworks prompt To exit telnet press
45. fferent lamp sources the user should experiment with the exposure time to verify there is sufficient flux for their science goals HERMES wavelength calibration uses 2 ThXe lamps that are currently installed on the 2dF calibration flaps directly illuminating the corrector lens Both ThXe lamps should be selected in order to get sufficient flux level in a timely manner The typical exposure times for arc exposures are given in Table 3 2 for both nominal and high res mask mode using these 2 ThXe lamps Note that because these lamps are shining directly upwards onto the corrector lens there is some concern of non uniform illumination and variation in the angle of incidence compared to star light The impact of lamp location on the resulting wavelength calibration is currently being quantified The values in Table 3 2 are approximate and only given for guidance These exposure times have provided sufficient flux for wavelength accuracy within 0 1 pixels and flat field counts to achieve a signal to noise of 100 per resolution element For different science requirements the exposure times should be adjusted 26 Table 3 2 HERMES Calibration exposure times CCD Mode Arc Exposure Flat Exposure sec sec BLUE Nominal 180 80 Mask mode 300 160 GREEN Nominal 180 80 Mask mode 300 160 RED Nominal 180 45 Mask mode 300 90 IR Nominal 180 60 Mask mode 300 120 27 28 Part II Preparing for observing 29 Chapter 4 In a
46. fferent places on the CCD moving the line pattern as a whole to the left or the right The principle of the focus technique is to measure these shift as a function of position on the CCD and then adjust the detector position Piston and Spectral tilts only the Spatial tilt is not motorized to minimize the observed shifts An analysis script takes as input a Left Right Hartmann pair smoothes the images to re duce the impact of bad pixels cross correlates 9 subregions of the images in a 3x3 grid to determines shifts and then returns suggested values to adjust the focus We recommend running the focus procedure every night a few hours before observing starts with the dome lights off The best focus values can differ between the two HERMES slits hence the focus should be set independently on both slits Once the best focus values are set it usually changes minimally day to day Below we outline the focus procedure 1 In the HERMES Spectrograph Control Window see Figure 9 1 click AutoFocus Hartmann The sequence of hartmann exposures will commence immediately after The exposure time is fixed at a value appropriate for the instrument resolution mode 180sec in nominal resolutions 300sec for list mask mode 2 The Automatic Focus window 9 2 will also pop up at the start of the script This displays the Piston Spectral tilt and Spatial tilt for all four CCDs for various settings which are filled in as the focus script proceeds T
47. fset between the star and the cross is due to a tracking error or offset The night assistant could manually move the star back under the cross as needed The object should now be centred over the fibre and data can be taken 80 Chapter 13 Using the ADC The 2dF ADC Atmospheric Dispersion Corrector gives good but not perfect correction for the effects of atmospheric chromatic dispersion for fields away from the zenith up to ZD 60 degrees The 2dF corrector is a 4 element optical system Two of the elements are slightly wedge shaped optical doublets which can be counter rotated to correct the atmospheric dispersion but NOT the effect of atmospheric distortion across the 2dF field They are designed to give zero deviation but in practice the centering of the 2dF field does vary slightly at the arcsec level as they rotate so it is important to wait for the ADC to start tracking before acquiring a field For some astrometric or focus test observations it may be best to stop the ADC tracking Although the ADC has its own control window see Fig the basic control of the ADC is most easily done from the Telescope control window of the control task via its SLEW page If you slew the telescope from here the ADC can be automatically slewed with it From here you can select one of the following modes ADC Track The ADC will track with the telescope ADC Null The ADC will set to a null position at which it has no effect ADC St
48. g with another instrument prepare finding charts for your targets Preparing FLD files is a complex task and should not be left until the last minute Astronomers are strongly encouraged to reduce their data in real time at the telescope Although such quick look reductions often require revisiting afterwards they are crucial to ensuring the best quality data is obtained AAOmega and HERMES data are reduced using the 2dfdr software environment Reduction facilities are available at the AAT and via the remote observing system but users may wish to download and run the software e g on their laptop The 2dfdr page provides all necessary links and information for the data reduction task 31 32 Chapter 5 Preparing field description files FLDs for Configure A brief note on terminology Running configure refers to working with the soft ware package called configure which allocates fibres to targets from a usually larger list of potential targets Although this software would probably better be called allocate it has it s name for historical reasons Configuring a plate refers to the process of reconfiguring the 2dF fibre focal plane using the 2dF Robot The work of determining the precise location to position the fibres in the focal plane is done as part of the tweak which happens just before the robot begins configuring a plate The configure software takes as input a text file that describes all p
49. gets at the expense of a large number of lower ones but also include these lower priority targets in a new configuration where possible There is a facility to lock fibres in place between configurations A simple way to cover multiple targets in a field using repeat observations is outlined in section 5 4 of the configure manual Multiple configurations to cover a target list The process uses the option to save the unallocated targets from a configuration to a file using the menu option File gt list in Configure While this technique certainly works and is discussed below it is limited in that it can be rather tedious to undertake and also cannot be done efficiently in advance of a run since the 2dF astrometric solution will change before the run and so many allocations will not be valid during the obseravtions A better solution is outlined in Example 2 below 8 1 1 Examples Example 1 Simple multiple configurations Starting from a large master catalogue 1 Allocate the field using configure 2 Save the sds file 3 Also save a lis file File gt List which contains the unallocated objects this is an option in the pop up that will appear then you select File gt List The lis file format for the unallocated objects is the same as that for an input fid file If you select one of the other save options the formatting will be a little different 4 Load this lis file into configure and rerun the configurati
50. he Current Position and Settings at Image Capture should be the same 3 Once the two set of exposures have readout the calculated pixel shifts will be updated in the Automatic Focus Window Inspect the suggested new settings and the difference 4 If the difference in pixel shifts is less than 0 1 then the focus is fine If not click the Apply button to move the selected setting to the suggested new value Clicking Apply Arm will move all mechanisms per CCD and clicking Apply All will move all CCDs 53 800 HERMES Spectrograph HERMES Control and Status Ctrl S a In ment Health click value for details Room Doors Room Lights s Position Trust PRA Fibre Mode Scrambler OFF To IE Ex changer Observation Sit ZE 2509944 Slit Dither Spectrograph Light Path Slit Mask Hartmann Shutters Dichroic 1 Name Dichroic 2 Name Dichroic 3 Name Shutters VPH Properties y Arm Blue Green Red VPH id GA Blue GA Green GA Red GA IR VPH line density linesimm 3827 3196 2785 2378 Central Wavelength 4833 5788 6642 7781 Blaze Wavelength 4833 5788 6642 7781 dispersion 0 0450 0 0550 0 0630 0 0730 order 1 1 1 1 Camera Focus Fois Spectral Tilt 200 8 200 6 200 2 200 4 Follows Slit Focus 190 0 280 1 290 3 320 0 Spectrograph Leds Plate 0 Back Rum Plate 1 Back Ilum a Auto Focus Hartmann Auto Focus Contrast Focus Mech
51. ht Assistant has a list of stars on file and can choose one if needed SNAFU stars are too bright 7th mag to focus accurately 2 Move the FPI to either one of the guide stars for the configured field using the Select Object window or if using another star centre the FPI by clicking Control Options Centre gantry no survey under Gantry Task Control right lower part of the FPI control window 3 Take an image of the star by pressing the Image button in the FPICTRL window 4 Check the quality of the image You may need to adjust the exposure time generally 2 4 seconds is suitable for a 12 magnitude star 5 Select Commands Focus Telescope from the FPICTRL window menu 6 Now select the number of steps and the value of the focus offset between them We suggest 3 steps either side 7 total steps and 0 2 mm focus offsets Click OK 7 The procedure then starts and it automatically drives the telescope through a range of focus values taking a centroid at each point and fitting a Gaussian to the image profile A plot is displayed of FWHM vs focus position and a fit is overlaid see Figure 12 2 One can then use the fitted minimum as the new default focus position 8 If unsure of the focus position either return to the initial focus or use the displayed minimum and repeat the procedure with an increased range Please note that seeing variability may play an important role here so you may need to modify the values given
52. iles 2 2 00 2 0 0000000084 10 Part I Overview of 2dF and HERMES Chapter 1 2dF Overview 1 1 Basics 1 1 1 What is the reconfiguration time For a full field reconfiguration i e to remove the old configuration and replace it with a new one the reconfiguration time is now of the order 40mins 1 1 2 What is the minimum spacing in arcseconds on the sky of 2dF fibres i e how close can observational targets be Actually it depends on the geometry at which the fibres come in due to the rectangular shape of the magnetic buttons The absolute minimum is 30 arcsec 2mm but typically it s 30 40 arcsec depending on location in the field and target distribution 1 1 3 A note on exposure time The atmosphere acts as a giant time variable due to changing Hour Angle HA chromatic lens The 2dF top end is eguipped with an Atmospheric Dispersion Corrector ADC which corrects for the chromatic component but atmospheric refraction changes the plate scale of the 2dF field plates as a function of HA or rather Zenith Distance ZD and there is no way to account for this stretch of the field Differential Atmospheric Refraction DAR during an observations Each 2dF configuration has a specified mid point for which the field is setup accounting for the effects of DAR at that time For a full 2degree field a configuration is typically valid for lhour either side of this mid point Smaller fields are valid for longer fields a
53. king allocations for repeat observing Please note In the discussion that follows it is assumed that you are trying to lock the allocation to the same field plate for which it was originally configured and that you are observing at a similar Hour Angle HA Trying to lock the fibres to the same targets on different field plates or for a very different HA may fail to configure due to fibre collisions It can often be useful to lock a number of fibres any number between 1 and 399 onto certain targets while still allowing Configure to freely allocate the rest of the fibres The classic example is that a field has been observed for 2 hours on one night and it has returned redshifts for half of the targets but the remaining targets need to be observed for a second 2 hours as per the original telescope proposal while adding in additional targets for the remaining fibres It is possible to force the allocation of some fibres on to previously observed targets and then reconfigure the remaining objects 49 8 2 1 The procedure for creating and using an import file 1 Load your fld file as normal and configure as normal 2 Save the sds file 3 Save a lis file using the File gt List menu option 4 Edit the list file to create a new file by default Configure is expecting a imp file The nature of the Edit is discussed below 5 Reopen your fld file NOT your sds file 6 Turn on Expert mode in Configure select the Expert flag in the
54. ld Therefore the following is really only necessary if one needs to confirm that the tracking is working or perhaps to confirm a raster sequence or other complex operation 1 Instead of moving the FPI clear move it to another position on the plate so that it does not vignette the target fibre choosing a fibre numbered less than 200 to start will help greatly This is most easily accomplished by dragging the FPI gantry image in the engineering interface to a suitable location Once dragged right click in the engineering interface to confirm the request Goto X Y moves the FPI to the actual position of the fibre on the plate while Goto RA DEC moves it to the current apparent position considering the atmosphere We want the arbitrary target to actually be centred over the fibre hence the choice of X Y 79 Ask the night assistant to manually change to the axis corresponding to the plate i e A for plate O and B for plate 1 Set the FPI to continuous imaging mode and look for a star The FPI Gantry Jogger can be used to make small movements to find a star With a star in the field stop the continuous imaging mode turn on the centroid calculation and take a single image A cross should appear in the skycat window corresponding to the position of the object Disable the centroid calculation and then restart the continuous imaging mode The cross will remain on the screen at the position of the star in the first frame so any of
55. most often used to acquire a field when the telescope pointing model is slightly out It can also be used to acquire objects such as standard stars or single objects which the field has not been configured to observe 1 Move the FPIto the position of the fibre of the object to be acquired typically a configured guide star by selecting it in the Select Object window and clicking Goto RA DEC 2 Take an image and identify the object to be acquired In the case of crowded fields it may be necessary to move the FPI to several objects and take images to determine where in the field the object corresponding to the currently selected fibre appears 3 Either e Control click on in the FPI SkyCat window This will offset the telescope to bring the point clicked to the centre of the FPI FoV e Choose Commands Offset Telescope to centre star from the menu to use the centroid algorithm to determine the point to offset 4 The software will automatically take another image once the offset is complete so you can confirm the object is centred The centre of the image can be marked using the Mark Centre button in the FPI SkyCat Window NOTE When using the FPI there can be some confusion about the telescope axis When the FPI is unparked the telescope will automatically switch to the REF axis When it is parked or Move This window disappears when the plates are tumbled Bring it up by choosing Select Object and Poscheck in the FPICTL C
56. nformation A ENS Ele ommends Magen Spions File finstsofti2dFitemp 47tuc_hermes1_p1 sds Camera Control Camera Status Gantry Moves Gantry Jogger Centre Position 2000 RA 00 23 10 00 DEC 72 04 40 00 2 Program id Exp time 1 ses Demand position Target field label NGC 104 RGB and AGB likely members W Open Shutter x 67262 v F37soz 8 Objects Object Selection 4 Calc Centroid 036 004519 IN Select Objects by Allocation Select Target Type Move Gantry 035 000710 All All EE E 4 Program Objects O Dl Actual position on plate 1 036 000577 W Allocated Bias 0 counts 037 000545 4 Sky Objects EEN Continuous x Soasi2 Y _ 293905 037 000668 Unallocated Objects E Fiduical guide epeal bb Bi p By Count Survey req Cox fatiado 4 Unallocated Guide for pos check 4 Unallocated targets PECERA Select d 243 bout 101269 38326 M Select maximum distance mm about x Camera Task Control Gantry Task Control gt E Ei 4 Pos check maximum distance Load x and y from Pivot 300 Status Dae Status Gantry Parked Object details Allocation bject Control Options Control Options ae es All green here means focus aperamre light path is a sensible configuration Hover mouse here for more info Comment Type F Messages Magnitude 12 738 Priority 9 21 05 00 Action MARK Task DSERV completed Sky Positi y a RA DEC 21 05 02 Centroid is 107 13 100 20 in window 263 13 256 20 on detector y Position 2000 100 20 57
57. ng but large slews do affect the fibre throughput probably at the lt 5 level 3 Alternately particularly for non configured locations such as standard stars the position information can be given directly to the night assistant 85 800 IX Telescope Control Telescope Control Ctrl T Al Status Zenith Eguinox 2000 Telescope Mean RA 14 31 16 93 DEC 31 13 12 2 App Place RA 14 32 06 71 DEC 31 16 42 3 Telescope HA 00 00 ZD 0 18 Time to Set 00 00 00 Airmass 1 00 Telescope UTC 17 Dec 13 22 48 55 Local Sidereal 14 32 05 Tracking System MOUNT A PO R FPI Ber Slew Park Offset Focus Instrument App and Focus Telescope Slew Control Position J2000 Config File Positions Mean RA Select source of file Mean Dec Observation Plate File Ade Control Config Plate File ADC Track Prompt for Config File w ADE NULL E oad position from file v ADC Static to input fields w ADC Ignore Commence Slew and Track Figure 14 2 2dF Telescope Control window Confirm that the ADC is tracking look for Tracking under the ADC in the HERMES Main Window After calibrations are complete ask the night assistant to set up the guiding e Ifthe Night Assistant asks for the plate rotator find the Clone Rotation to NA button which is under the Rotation tab in the Positioner Control window e Usually the field is acquired straight away by the Night Assistant If
58. nimize the chance of human error for example if taking an Object exposure it will check if the telescope is pointing to the centre for the field you have configured Users should read text in the warning message carefully before dismissing or cancelling the run If the reguested frame reguires lamps a box see Figure 11 3 for Arcs and Figure 11 4 will appear where the specific lamps reguired can be selected Calibration flaps if needed will automatically be closed during the exposure and opened at the end of the exposure unless they are reguested to be left closed for consecutive lamp exposures by selecting the Select to leave flaps closed button 65 X CCD Optio 8 O O X CCD Optio _ 2dF CCD Options dialog 2dF CCD Options dialog al Green colours indicate Green colours indicate default settings default settings Select Window Y m gt g 5 a Select Speed NORMAL NORMAL NORMAL NORMAL Select Amplifier 1 w pd o o A o o a ta 2 o gt pel q Set To Default SetTobefauts Set To Defaults Figure 11 2 Amps Speed and Binning selection Windows 11 2 Starting Up tdfct Typically the AAT technicians will start the control task for you If it is not running you should enguire with them before starting it This section is for advanced users only If you have not done this before seek
59. ns particularly in brighter guide stars Including proper motions in your FLD file is highly recommended Below are several warning when choosing guide stars e Simply selecting some bright guide stars from SIMBAD or GSC is NOT going to work your astrometric solution MUST be the same for the guide stars AND the targets and good to 0 3arcsec or better This is a reguirement for ALL 2dF fed observations 34 e 2MASS with UCAC and PPMXL sources have proved successful in recent years although the USNO survey seems to be somewhat inconsistent probably due to plate boundary effects e SDSS is an obvious source of guide stars However all stars need to be eyeballed as SDSS has funny artifacts at the magnitudes required here Marginally saturated stars which do not suffer obvious defects on examination have been found to still give excellent results e Eyeball your guide stars Reject galaxies reject binaries reject objects with junk magnitudes Stars should NOT be used blindly guide globular clusters are next to useless and stars should not have spiral arms e The target and guide star astrometry MUST be on the same system Simply using two different catalogues that independently claim to be J2000 will result in poor acquisition and low throughput An interesting paper on the effects of poor astrometry on Signal to Noise is Newman P R 2002 PASP 114 918 5 3 Format An FLD file is a structured text file with two parts The first pa
60. nt central wavelengths to use for different subsets of a target list i e one may want to look at RED and BLUE stars using a different central wavelength for each part of the target list This option is described in more detail in the Configure input description The figure below demonstrates the predicted strength of this effect graphically This figure has been created using the AAOmega Configure software The same fld file was configured 3 times each time with a different configuration wavelength 850 650 and 525nm here The sds files thus created were then investigated and the different 2dF field plate positions that would represent the correct position for each fibre as a function of configuration wavelength were extracted The figure shows the 2dF field plate with Parked fibres those not used around the edge of the field plate Program fibres are shown on the field plate as a black cross with an associated red and blue vector The cross marks the 650nm configure wavelength position while the vectors show the offset to the 850nm and 525nm positions As one can see from the plot 650nm marks the optimum configuration for this wavelength range so as to lose the least amount of light 14 across the full spectrum but giving a deficit at both the blue and the red ends The scale is given by the 1 arcsecond circle in the lower left corner The magnitude of the radial displacement is shown in the lower plot Note that the crosses at about zer
61. o ca seere e 10 4 Science Observing 10 5 At the end of the night 10 6 At the end of the run 11 The Observing GUI 11 1 CCD Control Window 11 2 Starting Up tdfct 11 3 Shutting down 2dF 11 4 Restarting 2dF 12 Using the Focal Plane Imager 12 1 FPI Imaging Options 12 2 Checking the seeing 12 3 Acquiring Fields with the FPI 2 2 00020 0000 12 4 Focusing the Telescope 12 5 Acquiring a target to an arbitrary fibre e e 12 5 1 Automatic Method 2 2 2 2 En rn nn 12 5 2 Manual Method 13 Using the ADC 39 39 39 39 40 40 42 43 45 47 47 48 49 50 50 50 53 53 57 59 59 60 60 60 61 61 63 63 66 68 70 73 74 75 75 76 77 Ti 78 81 14 Science Observing 14 1 Configuring a Field a 14 1 1 Making sds Files Available 0 o e 14 1 2 Configuring the field plate 2 2 CC on nn e e e 14 1 3 Hints for configuring fields o o e 14 2 Acquiring a New Field e 14 3 Taking Datang b e ea Me a ne a rc 14 3 1 Typical Observing Sequence nn nn 14 3 2 Multi Fibre Flat Fields FLATs 14 3 3 Wavelength Calibration Frames ARCs 2 o 14 3 4 Object Frames s cacet oo e nn 15 Additional Science Calibrations 157015 BIAS frames ssa ns sa RN NM KAN Rn Ve ha na Ei ee we A 15 0 6 DARK frames zu image go w
62. o correspond to the guide star fibres which are placed at 5000A for the guide camera in all configurations the small shifts seen here are due to changes in the effective centre of the configuration at the different wavelengths A direct demonstration of the actual effect of CVD is shown in Figure 5 of Cannon et al AAO Newsletter Feb 2008 p26 30 This was created using the raster scan technique on a set of observations of relatively bright stars and finding the centroids of the stellar images The pattern agrees very well with the predicted effect shown below There is more discussion of both the ADC and the dramatic effects of CVD in Cannon et al AAO Newsletter Feb 2000 p14 15 The conclusion one reaches is that for fibres with 2arcsec diameter the best fibre placement when the acquisition of the Red and Blue light is key to a project is usually to place the fibre for a central wavelength and accept losses at each end of the wavelength range An excellent paper on the magnitude of placement errors of this kind is Newman P R 2002 PASP 114 918 Predicted CVD 850 650 525nm x E acd t 108 CM rg 19 e atataka A 3 Ni E 4 per x x N NT al BN EDS AFR f A SS AI Ph gt a h x PE x Pe iia NX 4 A A i s E TN TE SI ERA SL e SAA E g x 0 N J 2x10 2x10 0 2x10 o resec r fa ta o o on x MM xik Me x 0 2 0 4 0 6 0 8 Radius degrees E 5 E peran mui TRE A graphical demon
63. ommands menu 3The AAT has three computer defined axes REF A and B Switching between these axes offsets the telescope by asmall amount defined by the APOFF ostensibly to change between an acquisition camera and an instrument 75 cleared the telescope will switch back to the appropriate axis for the observing plate A 0 B 1 Generally this is seamless but can be confusing especially during some operations If the telescope is in the wrong axis when centring then the offset will be incorrect Alternately if the telescope is not switched to the correct axis for the observing plate then light will not fall on the fibres on the plate when taking an exposure using the instrument In any case once the telescope offset has completed another single FPI image is automati cally taken you should check this image to make sure the star is centred 12 4 Focusing the Telescope The first setup to do once it gets dark is to focus the telescope The telescope focus is not fully temperature compensated the metal structure of 2dF in particular so it is advisable to re check the focus if there is a large temperature change or the seeing improves Once familiar with the process it can be done in 90 seconds The normal range of the telescope focus value is 36 0 39 0 mm 1 Point the telescope at a suitable star Guide stars from the first science field are good although if the field is a long way over a star closer to zenith may be better The Nig
64. on saving a new lis file of the outstanding unallocated objects each time Example 2 Configuration using a master catalogue and current status list For the reasons below Example 1 above is not the preferred approach for most programs 1 For the first run in any 2dF observing block the astrometric files will not be available prior to the run and hence the configurations would be invalid if prepared in advance This is typically only a small effect but is compounded with each new iteration 2 The fibre availability of the field plates will change with time during a run due to the slow rate of fibre attrition 3 No accounting is made for data quality once observations have begun 4 There is little flexibility between the interchange of the two 2dF field plates during obser vations 48 The solution is to prepare a master catalogue with target observation priorities for your full observing region and to create a processing script to draws sources from this catalogue based on external constraints For example 1 Choose the first pointing centre for observation 2 Make a fld file select 500 800 high priority targets from the master catalogue The UNIXgrep and awk commands are ideal here or a simple Perl script may be the best way to achieve this goal 3 If there are a small number of high priority targets pad out the fld file with lower priority objects Care should be taken if a large number of low priority targets
65. ositioning optimisation Can be repeated up to nine times where n is from 1 to 9 The wavelength must be specified in angstroms and in the range 30004 to 100004 optional PROPER MOTIONS Determines if the input file includes proper motions optional does not take a value 35 Any non comment line that does not start with one of these keywords will be assumed to signal the start of the target list Columns of the target list are separated by one or more spaces Each line ends with a comment column which can include spaces The equinox of all coordinates given in the file must be that specified in the EQUINOX line The columns are Name The name of the object by convention Fjnj is used for reference stars The name cannot contain spaces but underscores are acceptable Right ascension in the format hh mm ss ss The sexagesimal rounding must be correct 22 60 34 5 is an error as is 22 45 3 i e no seconds and decimal minutes Decclination in the format dd mm ss s As above the sexagesimal rounding must be correct Position type One character indicating the type of object P program science target S blank sky F guide star If a WLENn item has been defined in the header that wavelength is assigned to a program target using P_wn in place of the P and with the n corresponding Target Priority 1 9 with 9 being the highest priority If you are not using priorities you should set all priorities to the same value say 1
66. ospheric effects The upper panel shows the distribution of targets across the field in units of microns this plot is in 2dF robot coordinates with North to the right and East at the top The vectors have been multiplied by a factor of 800 to make them visible The circle in the bottom left hand corner indicates the size of a 2 arcsec diameter fibre on the same scale The lower panel shows the lengths of the vectors in arcsec i e the total error plotted against radial position in the field The mean error in this case is 0 15 with a maximum value of about 0 4 A dominant rotational effect is visible this component would be corrected by the 2dF field plate rotation mechanism In this case it is possible to observe 2hour either side of HA 0 even if plate rotation was not available 17 Field distortion 0 3h 20d 2x 10 2x10 0 2x10 2 A 2 1 5 ha amp 4 he o 0 5 he 7 x x El 0 gt 4 gt 5 xi ad i n 0 0 2 0 4 0 6 0 8 1 Radius degrees Here we see the same plot as above but this time with the end of the observation 3 hours away from the transit configuration time A field plate rotation has been applied in this instance but we see that the uncorrectable error for many fibres is above the fiducial 0 5arcsec level even after rotation has been accounted for This next bit gets a little tricky But it s important Most novice 2dF users should probably call their support astronomer about
67. ossible targets to be observed The file is usually referred to as an FLD file after the regular fld extension in the filename General guidelines and suggestions for FLDs are discussed first followed by instructions for including guide stars and finally a description of the format is given All of this information is critical to the success of a program so pay careful attention 5 1 General Guidelines for FLD Files Number of targets Include no more than 800 targets More targets will make configure run very slowly which can be problematic with the time requirements at the telescope In any case check how long your field requires to allocate Allocation times of 1 hour are not uncommon for overly dense fields or two many targets and can cause considerable problems at the telescope Magnitude Range of Targets Typically a range in magnitude of up to 3 mag is reasonable Larger ranges increase the possibility of cross talk detrimentally contaminating neigh bouring spectra although improved extraction technigues can mitigate this Talk to your support astronomer if a larger range is desirable Calibration sources Many teams include calibrators within each field If reguired these should be set to Priority 9 in the fld file with the priority of all science targets shuffled to lower levels so that the calibrators are always allocated These must be chosen to be of similar magnitude to science targets to avoid contaminating science spec
68. r onto the chosen guide bundle The Night Assistant should now centre this star by offsetting the telescope NOTE This offset can take some time if all of your guide fibres are at the edge of the field plate The offset can also be rather inaccurate over the full 1degree and so the Night Assistant may have to hunt a little for the star 8 Once the star in centered click the next button along the sequence Offset telescope to centre star on fibre This offsets from the Guide bundle to the chosen science fibre 9 Once the telescope has settled press the Taken image button at the end of the sequence in the control and follow the on screen prompt to set the standard star identification 10 Finally check that the spectrum looks OK and is not saturated If the star is to be placed down a number of fibres the sequence can be operated in reverse by pressing the appropriately labelled buttons on the control GUI If a new guide fibre is required then the offsets should be removed to place the star at the centre of the field and then the control tool can be closed and re open with a different pivot point selected For a different star the control tool can be closed and the telescope slewed to a new star 12 5 2 Manual Method This section is for advanced users only If you have not done this before seek help from AAO staff before proceeding This method depends on using the FPI to centre an object above a given scien
69. r the night s observing e g 2dF config oct13 20oct 14 1 2 Configuring the field plate Once the sds file is in place the configure is set up and started using the Positioner window Figure 14 1 1 If the plate to be configured is not in the configure position click Tumble in either the Plate 0 or Plate 1 tab to exchange the plates 2 Under the Wavelength tab set the spectrograph central wavelength The autoguider default of 5000A should not be changed except on expert advice 3 Under the Weather tab set appropriate values for the weather at the start of the observa tion Except for fields configured during the afternoon the best is to use the Met System values Select Using Dialogue then the Fetch button will update the values with the current conditions 83 800 IX Positioner Control 2dF Positioner control dialog Ctrl P a Config Plate gt 0 Details Plate O Plate 1 Config file instsoft 2dFitemp PM test tifsds t 2dFitemp 47tuc hermesi pL sds Fibres Moved 4 7 All Parked A 7 N amp S Mask On No No Plate 0 Plate 1 Rotation Weather Wavelengths Flags FF Do Tweak for an offset of 100 minutes w for local time wv file proposal date Duration hrs 1 Explain this 4 Optimize using box Config file Find File Configure Fibres Park All Tumble Configuration Progress Figure 14 1 2dF Positioner Con
70. racking independently of the stationary telescope In this case it is necessary to stop the ADC from the ADC control panel Occasionally this command is ignored in which case simply null the ADC which moves the ADC elements to their nulled position and leaves them stationary Alternatively if the telescope is parked at zenith or PF access using the 2dF control system the default command will automatically stop the ADC Unknown at this time if this mode of operation is affected by the problem above Please do not forget to stop the ADC tracking at the end of the night 82 Chapter 14 Science Observing 14 1 Configuring a Field Before configuring a field in the afternoon the instrument must be released to the observers Check with the AAT staff that no work is being performed on the instrument and that it is safe to begin configuring Configuring a field is the process of moving the fibres around in the telescope s focal plane for a new field As input this process reguires an sds file that is the output of running configure see Chapter 6 Using Configure 14 1 1 Making sds Files Available The sds file must be copied to a directory that is accessible to the robot Typically the user should copy the sds to a subdirectory of configs This directory is available on any of the computers in the control room Then on the instrument control computer aatlxy the file is copied into a directory fo
71. rchased later in order to cover other science domains 2 3 Spectrograph Focus The HERMES spectrograph is focused by moving the CCDs Each CCD is mounted on a moveable stage within the dewar which provides three degrees of freedom overall piston a tilt along the spatial axis and a tilt along the spectral axis Only the piston and spectral tilt focus mechanisms are motorized The spatial tilt is fixed at the nominal best position such that all fibres fall within the boundary of the detector The spatial tilt should only be moved manually by technical staff The spectrograph is typically focused each afternoon The best focus values can differ be tween the two HERMES slits hence the focus should be set independently on both slits Once the best focus values are set it usually changes minimally day to day Note HERMES is sensitive to temperature changes in the spectrograph room such that if there have been heavy daytime activities in the room or the room door was accidentally left open the spectrograph focus should be checked prior to starting the science observations Good focus minimises cross talk between spectra on the detector and ensures the fibre tramlines can be accurately identified in the data reduction process 2 4 References e Integrating the HERMES spectrograph for the AAT Heijmans et al 2012 SPIE 8446 17 s e HERMES revisions in the design for a high resolution multi element spectrograph for the AAT Barden e
72. rcsec ThetaMax arcsec Straighten Fibres Collision matrix filename Random Seed Percentage of allocations sampled Number of background threads to use Number of AAOmega fibres to assign to sky 460 460 fi 3 000000 w Quick Standard 4 Weight Close Pairs fo 650 4 CrossBeamSwitching never moderate heavy collision matrix W Enforce sky quota E Weight peripheral fiducial targets 4 Weight fiducial target pairs On the fly collision calculation E pss Close Figure 6 2 Allocation options in Configure 44 Chapter 7 Planning 2dF observing with obsplan The ObsPlan tool is used for planning a night of 2dF observations Assuming a starting time for the night usually 15 minutes before the end of astronomical twilight and introducing the expected changeover time between plates ObsPlan computes at what time and airmass a field plate identified by name RA and Dec can be observed This tool also takes into account the time that 2dF needs to configure a plate and that field plates have to be configured alternatively i e you cannot configure two consecutive fields on the same plate if you do so the configuration time will be added to the planning time ObsPlan is intuitive to use and very helpful as it provides the starting times for configuring 2dF see Section 14 1 2 as well as the middle and final times and airmasses for the observed field
73. red distance The whole process takes only a few minutes On a recent observing run we managed to observe 5 standards in the dawn twilight the longest part of the job being the arc exposures Care should be taken with the large offsets greater than larcmin as at this level the star may not centre on the fibre well There is no way to account for this centering loss even for small offsets and so such calibration can only ever give a relative flux calibration within the spectrum An absolute calibration can only be achieved by normalising the observed spectrum to an external photometric measurement Standard spectra can be readily extracted and reduced using 2dfar Time Reguirements Plan on at least 15 to 20 minutes to observe one standard star following method 1 described above This takes into account the time to acguire the star and offset to the guide and spec troscopic fibres and the exposure and readout times including calibration This number also assumes you are using normal readout speed and observing reasonably bright standards 14 mag or brighter at low dispersion more time will be reguired for fainter standards higher dispersion or slower readout Remember to take any reguired flats and arcs This is especially important if a slit unit has been moved or if flats have not been taken recently 91 Useful Information about Standard Stars Use the Flux Standard run type when taking exposures of the standard We have foun
74. rs when allocating a field for Cross Beam Switching obser vations For users who do not wish to use Simulated Annealing a version of Configure which uses the original Oxford algorithm is also packaged with Configure7 3 and later packages All you have to do is tar and unzip the appropriate gzipped tar gz file e g for the Linux 32 or 64 bit version tar zxvf configure 7 Linux Intel64bit tar gz 6 2 Running Configure 6 2 1 Updating the 2dF Distortion Model NOTE This is only required when running configure on your home computer The software at the AAT automatically uses the latest files To correctly allocate fibres to science targets configure must have an up to date model for the 2dF astrometry and knowledge of which fibres are functioning Both of these change regularly whenever the poscheck is redone or a fibre is broken repaired These files are not included with the distribution of configure and must be obtained separately and should be updated regularly The files required are listed in Table 6 1 The necessary files can be fetched by anonymous ftp from the AAO ftp site ftp aao gov au pub local 2df latest config files ftp ftp aao gov au pub 2df 39 Table 6 1 2dF Distortion Model Files tdFlinear0 sds Plate O Linear Coefficients tdFdistortion0 sds Plate O Distortion Information tdFlineari sds Plate 1 Linear Coeflicients tdFdistortioni sds Plate 1 Distortion Information tdFconstantsDF sds
75. rt is a header The header consists of keywords which determine certain characteristics of the whole field such as field centre and also can affect how the rest of the file is interpreted by the software The second part consists of a whit space separated table of potential targets for observing Each line can have up to 256 characters and comments can be indicated using either an asterisk or hash 4 character Special characters particularly quotes should be avoided The header consists of a set of keyword value pairs one per line The keyword is first on the line and separated from its value by a space Everything after the space to the end of the line is taken to be the value The keywords are LABEL A string giving the target field label which will be stored in the header May include spaces UTDATE The UT Date of observation In practice the date is not important because configure assumes the field will be observed when overhead 4 hours The format is yyyy mm dd dd The dd portion is optional and specifies the time as a fractional part of the day CENTRE Field Centre R A and Dec The format is hh mm ss ss dd mm ss s The sexa gesimal rounding must be correct 22 60 34 5 is an error as is 22 45 3 i e no seconds and decimal minutes EQUINOX Coordinate equinox for the rest of the file e g J2000 0 optional defaults to J2000 0 ARGUS not used for 2dF WLENn Defines specific wavelengths for individual target p
76. s arcsecond the plate scale to determine the offset Fibres at positive X and positive Y will require offsets south and west respectively For example Plate Position of Fibre Telescope Offsets X Y DEC RA 36761 14137 565 N 217 E 101391 38045 1559 S 585 E 7 Ask the night assistant to make the required offset via the Offsets tab on his or her interface 8 With the object selected in the Select Object window of the FPI click Goto X Y not RA DEC 9 Take another image with the FPI camera and identify the object to be acquired Depending on the size of the offset it may not be in the centre of the field If necessary use the full window of the FPI camera Commands Set Window Confirm that other nearby objects appear as expected 10 Centre the object with a Control Click Centre it again with a centroid box shift drag and Commands Offset Telescope to Centre Star Repeat the latter until the telescope offsets returned are small displayed in the messages area of the FPI window 11 If only a short exposure is required then it is easiest to now move the FPI clear and take the image Between frames the FPI can be driven back to the position of the fibre and the centring confirmed If a long exposure is required then it is possible to use the FPI as a poor man s guider Keep in mind that the AAT tracks very well and routinely can track for an hour or more without guiding and not drift off of a fie
77. s generally quite accurate but large offsets may give mixed results If accurate placement of a guide star is required the manual method may provide better accuracy but obviously is more difficult The basic procedure is to centre a standard star in a guide fibre then use a blind offset to put the standard star down a spectroscopic fibre For this reason the spectroscopic fibre should be as close as possible to the guide fibre within 20mm 5 arcmin if possible for best results The default is 50mm 12 5 arcmin but this is a little large 1 Inspect the configuration and choose a guide fibre which lies close to program fibres and near the 2dF field center Using Fibre 200 is best if possible since it means the spectra will land near the centre of the CCD One might consider also using the end fibres for radial velocity standards to check for PSF degradation 2 From the FPI control window choose the select object item from the commands menu Click on the allocated button and on all Then select the chosen guide star from the pivot menu and set the maximum distance parameter to a small value 20 50mm This should leave a list of a few star fibres if there are too many or too few change the maximum distance 3 Click on the standards button in the bottom right hand corner and a new dialogue box will appear This is the offsets calculator Select the guide fibre from the select guide pivot s
78. select the Save Settings button to save the current focus values for the slit used A window as shown in Figure 9 4 will come up asking to confirm the settings Select Save current settings as the new standard This will ensure the correct settings are applied each time you tumble between slits Repeat the above steps for the other slit and ensure both sets of focus values are saved In the HERMES Spectrograph Control Window select the Focus Follows Slit button to ensure the focus values automatically change to the saved values when you tumble between slits 56 Part III Observing with 2dF HERMES Chapter 10 Outline of observing This chapter provides a quick overview with links to the various detailed descriptions elsewhere in this document 10 1 During the Afternoon 1 Confirm Instrument Setup and preparation with support astronomer afternoon tech a Check the resolution mode is correct and the slit mask is installed if needed b Check with the technicians that the vacuum gauges are off and no lights are on in the spectrograph room 2 Confirm computing setup a Make sure you are ready to reduce data with a recent current version of 2dfdr on either an AAT data reduction machine or your laptop Note the best version to use is typically that on the AAT computing system 2 Confirm the correct idx file s for use with 2dfdr are available rn O Confirm that you can use configure on aatlxa If you will b
79. serving standard stars by blind offsets into conveniently placed fibres 2 Configuring a specially designed field with a guide fibre and spectroscopic fibres near the centre of the field plate The former procedure is advised if you only want to observe one standard star at a time the latter procedure is much faster if you want to observe several standard stars say at the end of the night Using an existing field configuration Use of specialised field configurations for standard stars An alternative procedure is to set up a few fibres in a special configuration This involves placing one guide fibre at the centre of the field plate and a pair of target fibres immediately adjacent to it offset 40 60 arcsec to the north and south The optimum set up is to put fiducial 200 or 400 at the plate centre and a number of science fibres over a range of AAOmega slit positions 1 and 2 arcmins north and south A number of sky fibres can also be allocated if reguired A dummy configuration centered at RA 00 00 00 and Dec 00 00 00 can be easily created by the user An example can be found at m2dF config standard star config P2 sds To observe a standard star or any single target bright enough to see in the fiducial display you simply 1 Point the telescope at the target 2 centre it up with the FPI 3 move the FPI clear 4 ask the Night Assistant to centre the target in the fiducial bundle 5 and offset the telescope N or S the regui
80. set skys can now be taken 60 10 5 At the end of the night Ensure all calibrations are taken for the last field of the night Any further calibrations such as bias frames or darks can be taken at the end of the night 10 6 At the end of the run Taking the data away Once the data have been taken and localized see Section the visiting astronomers can copy their data Section That is usually done at the end of the night or at the end of the run 61 62 Chapter 11 The Observing GUI The observing GUI or control task that manages the instrument is called tdfct for the Two Degree Field Control Task The basic software is shared between 2dF A AOmega HERMES SAMI and KOALA Typically the control task is brought up by the AAT technicians before you arrive If it is not running it is necessary to check with the afternoon tech before starting it 11 1 CCD Control Window Data acquisition is controlled via the CCD Control window Figure 11 1 At the top the status of the four channels are displayed Green indicates the channel is available and displays as idle During an exposure the panels turns to blue and displays as Observing Next the CCD Telemetry information are displayed indicating the current dewar temperature and the heater voltage per channel Below this are four panels corresponding to the exposure status of each channel When idle the panels are white during exposure a green bar
81. standard exposures such as Fibre Flats and Arc frames the standard exposure time is pre loaded into the boxes upon selecting the observation type Ensure the exposure time is correct for all cameras prior to starting the exposure The Sky Subtraction modes are defined in XXX None is set as default The Select CCDs buttons allows one to choose which channels CCDs are used All should be selected by default The Repeat Mode selection can be a Single frame Continuous frames until manually stopped or a Count number of repeats The number is set in the box below Count Options for selecting CCD readout amplifiers windows and readout speed are accessed using the Amps Speed Windows button The default modes are displayed in green and any non standard setting is displayed in orange See Figure The Seeing box allows the observer to enter the seeing value at the time of the exposure which will be written in the header The Plot Fibre Errors button when selected generates a plot to be displayed upon starting an observing seguence which shows the difference between the physical location of the fibres on the plate and the actual location of the targets The difference is the result of atmospheric affects not accounted for by the 2dF corrector Finally Start CCD Run starts the reguested exposure A warning dialog may appear at this point These warnings result from various checks done to ensure you are taking data which are valid and mi
82. status of fibres is taken into account Therefore the ideal 2dF program has of the order of 400 targets per 2degree diameter field and a uniform target distribution with no closely spaced targets Unfortunately nature does not work like that This results in extended target lists with multiple priority levels and strongly clustered source distributions The Configure software is necessarily generic requiring the observer to carefully define input target lists The main points to consider are e Number of targets In most cases and particularly so for the default Simulated Annealing Configure algorithm simply passing a list of gt 1 500 targets to Configure will not produce optimal results With around 350 400 fibres available per configuration target lists should normally be re sampled to include only a small excess of targets to fibres in the input file 800 1000 targets works well for relatively uniform fields lower numbers are needed for more compact fields e Repeat observations In surveys where the same or overlapping fields will be targeted 47 multiple times it is often advantageous to reallocate targets between observations This can increase the total target yield by rejecting targets that are confirm to have unwanted spectral types or replacing objects for which the spectral quality obtained is already sufficient e Locking a sub set of allocations You may wish to force the repeat observation of a sub set of high priority tar
83. stration of CVD effects in the 2dF prime focus corrector Note how the effect is most important between 1 2 and 2 3 of the way out towards the edge of the field plate 1 2 4 Field distortion Differential plate scale and ZD Why you should restrict your range of Hour Angle during an observation A final effect one must consider is the differential plate scale stretch induced by the atmo sphere at high ZD This is also due to atmospheric refraction but this time differential with 15 respect to position in the wide field it is close to monochromatic to first order It could only be fully corrected for by moving the fibres on the 2dF field plate to new apparent positions However this is not practical with 2dF since it would involve re configuring the entire field The atmosphere modifies the true RA Dec of one s targets to an Apparent observed position Over a 2degree field of view this modification has significant variations in magnitude with changes in HA What is more as the Hour Angle changes the size of the modification changes significantly as a strong function of field plate position While the full effect is complex shift in apparent position across the field and depends in detail on where one is pointing on the sky the effect can to first order be considered as three components 1 Translation of the field centre taken out by telescope tracking 2 Rotation of the field taken out by the 2dF field plate rotation mechanism
84. t al 2010 SPIE 7735 19 23 24 Chapter 3 Calibrations and Overheads In this section we discuss the overheads incurred and the minimum calibration requirements for HERMES data 3 1 Detector Settings HERMES CCDs can be readout using SLOW NORMAL and FAST readout modes with 1 2 or 4 amplifiers Tables 3 1 show the gain readout noise and readout times for the various readout modes using a single top left amplifier The values for other individual amplifiers are very similar to those in Table 3 1 A faster NON ASTRO readout mode is also possible but not supported for science observations due to known spurious effects This mode is only made available for engineering tests Using the two Left amplifiers or two Right amplifiers readout the detector in the spatial direction where fibres 1 200 are readout with the bottom amplifier and fibres 201 400 are readout with the top amplifier This avoids splitting the data in the spectral direction and is the default amplifier setting Using two Top amplifiers or two Bottom amplifiers readout the detector in the spectral di Table 3 1 HERMES Readout Modes CCD Mode Readout time Gain Read Noise sec e ADU e7 BLUE Fast 144 2 6 4 1 Normal 282 1 8 3 2 Slow 420 1 2 2 9 GREEN Fast 144 3 0 4 4 Normal 282 2 0 3 1 Slow 420 1 4 2 6 RED Fast 144 31 4 9 Normal 282 1 9 3 1 Slow 420 1 4 2 9 IR Fast 144 2 7 4 4 Normal 282 1 5 3 5 Slow 420 0 7 3 0 25 rection
85. t high airmass are only valid for short time periods Losses due to fibre position mismatches this is in no way an error within 2dF it is the Earth s atmosphere which is at fault can be significant outside of this time window An excellent paper discussing the full horrors of the effect is Newman 2002 PASP 114 918 13 1 2 Chromatic Variation of Distortion 1 2 1 The Chromatic Variation in Distortion of the 2dF prime focus corrector and the effect of the Earth s atmosphere The prime focus corrector of the 2dF telescope top end is essentially a 4 element corrector incorporating an Atmospheric Distortion Corrector ADC It is charged with not only delivering the un vignetted 2degree field at the 2dF field plates but also creating a flat focal plane with nearly constant plate scale projected fibre diameters vary between 2 0 2 1 arcsec across the field plate and without creating large non telecentric angles The subtleties of this have a very real impact on 2dF and AAOmega operations Lewis et al 2002 MNRAS 1 2 2 Does the Atmospheric Distortion Corrector ADC work correctly The first two elements of the prime focus corrector are both prismatic doublets counter rotated to compensate for atmospheric distortion The ADC is actively controlled and has been operating correctly for many years now and regular tests indicate that the ADC correctly compensates for atmospheric dispersion 1 2 3 Chromatic Variation in Distortion CVD CV
86. t in the HERMES position will pop up see Figure 11 6 If you are sure the HERMES mechanisms have not been moved since last clean shutdown then proceed with Trust button Ask the afternoon tech staff If unsure click Don t Trust and all the mechanisms will be moved to the home position prior to making any subsequent moves To bring up the various control windows click the more button under the corresponding part of the system in the 2dF Main Window The FPI window starts up minimised and can be found in the task bar at the bottom of the screen 11 3 Shutting down 2dF This section is for advanced users only If you have not done this before seek help from AAO staff before proceeding NOTE It is important to realise that if there have been positioning problems or errors then you should NOT attempt to shut down 2dF without expert technical assistance by phone or in person particularly if the gripper is carrying a fibre when it is stopped These are the steps needed to perform a regular shutdown of 2dF 1 From the main tdfct window choose the exit option from the File menu item 68 800 IX 2dF Control Task HERMES File Commands Display Windows Options Help E Control Task Status UT Time 17 Dec 13 22 37 51 Telescope Time 18 Dec 13 09 37 51 Telescope E ADC m HERMES Unknown ic Obs Slit 00 00 00 00 i Shutters UNKNOWN more more more Positioner Calibration
87. the observing position We find 3x 3 minutes gives good results however remember in skyflats you have to keep changing the exposure time between each exposure Furthermore longer exposures are probably reguired for high resolution in the blue Select Offset Sky for these observations and choose exposure time etc in the usual way When working in crowded or messy fields e g globular clusters nebulous regions large initial offsets up to 1 2 degrees may be reguired to avoid having too many objects landing in fibres 15 2 Standard Stars Here we discuss observing standard stars through individual fibres for instance to observe radial velocity and spectrophotometric standard stars This is still a time consuming process taking at least 15 minutes to observe a standard The observer has to supply the 2dF Support Astronomer with star positions for the current epoch including proper motions for nearby white or red dwarfs as J2000 coordinates However an offsets calculator is available and built into the 2dF control system Please note that it is not feasible to achieve good guantitative spectrophotometric calibration of the full set of 2dF fibres thanks to fibre to fibre variations and the effects of several chromatic distortions in the input images Most spectroscopy of individual stars is done to calibrate line strength indices or radial velocities 90 Two basic procedures are possible 1 Using an existing field configuration and ob
88. the requested configuration fails this test then the robot will not be able to configure the field It is 84 e Does a survey of the plate to be configured with the gripper gantry note the FPI Gantry cannot be moved while this happens e Moves all the fibres to their new positions for a full field this takes 30 50 minutes 14 1 3 Hints for configuring fields Changes in Fibre Status If during the course of an observing run the status of the fibre changes usual with broken fibres being disabled then the user may want to re configure the sds file The tdFconstants400 sds file on aatlxy is updated by the 2dF software every few seconds The version of the file on the configure web site is only updated at 8 30am each morning If configure is run on aatlxa the updated version will be used On the user s own computer the new files will have to be obtained from aatlxy instsoft 2dF positioner tdFconstantsDF sds Configuring a field without parking unused fibres The default mode of operation is for the positioner to park all unused fibres in a new configura tion However in some circumstances this is not the behaviour which is required For example if the new configuration is to observe a few bright stars at the end of the night then the ob server might not want to spend a lot of time parking the unused fibres To change the mode of operation select the flags tab on the positioner subwindow and click on the right hand button provided
89. to the focus procedure When you are more confident of the right focus you can decrease the number of steps and the focus offset 9 The Night Assistant can also set the focus to a value used on a previous night if necessary The FPI camera saturates at 65 000 counts 76 Figure 12 2 Textbook example of a focus run with the FPI camera The red crosses indicate the different FWHM values y axis in each of the seven exposures used at different focus values x axis The magenta cross indicates the initial focus of the telescope The blue and green lines are linear and parabolic fits to the data In this case the best focus value is 38 8 mm which gives a seeing of 5 pixels 1 5 arcsec 12 5 Acquiring a target to an arbitrary fibre There are two methods for acquiring an arbitrary target such as a standard star to an arbitrary fibre on the plate The automatic process walks you through the process but a manual process is also provided for unusual circumstances such as large offsets Keep in mind that the automatic process does a blind offset while the manual process will guarantee the offset by using the FPI to centre the object over the desired fibre 12 5 1 Automatic Method TO DO Confirm that this method actually enables the buttons I think there is a step missing talk to Sarah M NOTE This method does a blind offset to bring the object from a known position the guide fibre to the science fibre Offsetting the AAT i
90. tra Drawing the calibrators from the recent sample of White Dwarfs and Hot Sub Dwarfs of Eisenstein et al ApJS 2006 167 40 from SDSS has worked well Absolute flux calibration is limited by the unguantifiable aperture losses both in position and size of the aperture in any given 33 observation and by fibre throughput variation primarily from FRD within the retractor mechanism However including a standard star in each field plate observation can im prove the guality of internal spectral calibration and monitor data guality during a run All caveats relating to astrometric accuracy apply to calibrator data as well as science and guide data Sky fibre positions You will need 20 30 sky fibres in the observation so 50 100 possible sky positions should be enough Eyeball the sky fibre positions to check they are actually blank regions Assigning Specific Wavelengths to specific targets The telescope s Positioner GUI also handles atmospheric refraction effects when working out the positions of fibres on the field plate including the effects of chromatic variation of distortion Normally a single wavelength is chosen for all fibres and is applied at the time of observation However it is possible to optimise individual fibre placement for one of up to nine user specified wavelengths Target priorities The simulated annealing algorithm is very good at allocating targets based on the 9 possible priority levels 9 is highest priority Ho
91. trol window e NOTE 1 Write these values down in case of software crashes If you don t record these values and have to restart the positioner mid configuration you may be faced with a time consuming tweak to positions if conditions change A convenient log sheet can be found at 2dF config LogSheet_conf ps e NOTE 2 If configuring during the day remember to set realistic night time tem peratures etc Check the Met system and guesstimate the temperate based on what it was 24 hours ago and the current trend 4 Select the Plate tab for the plate to be configured 5 Set the start time in 24h local time and duration in hours of the observing sequence for the field which is known as the tweak NOTE Tweaking a field does not change the actual time a field is valid for which is fixed by the physics of the atmosphere and 2dF corrector system It just sets how the software will configure the field to get the most possible light down the fibres over the period observed however little that might actually be Generally fields are valid for up to two hours sometimes much less See X XX for more information if you are confused 6 Select the configuration file by clicking the Find button and finding the file in the file system 7 Finally press the Configure fibres button to start the configuration The system then e Checks that the configuration including tweak is valid i e no fibres will collide If
92. ttons toggle select which subsystems should be cleaned up on shutdown Normally local system should be selected Ask Tony for clean up GUI images 11 4 Restarting 2dF When restarting 2dF during the night a complete logout from aatlxy is not required The two main actions to carry out prior to a restart is to power cycle 2dF and the CCD controllers if needed Here are the steps to follow to restart 2dF 1 First shut down 2dF following steps included in the previous section Sect 11 3 2 An internet power switch allows the power to the 2dF top end to be cycled from the control room via an internet browser To use the system follow these steps a start up a web browser on any machine on the AAT network The power switch is bookmarked on the browser tool bar for reference IP address for the switch is 70 Figure 11 7 2dF internet power switch window 10 88 90 66 This should pop up a password request box You do not need a password just leave the entries blank and click OK DO NOT click Cancel A web form interface to the 2dF top end network power switch will appear see Fig 11 7 Select the Boot radio button from the form for the VME Crate and then hit the Apply button to reboot the top end power supplies VME crate Finally although the system has a 2 minutes auto time out on it click the log out button to exit the system Now wait for the two boot messages to appear on the aatlxy The pop up window notifying the reboot o
93. u na wa ea ER ea 15 0 7 Long Slit Flat Fields ok 15 1 Offset Sky Frames 2 22 aa 15 2 Standard Stars IV Data Reduction using 2dfdr 83 83 83 83 85 85 86 86 87 87 88 89 89 89 89 89 90 93 List of Figures 2 1 6 1 6 2 9 1 9 2 9 3 9 4 11 1 11 2 11 3 11 4 11 5 11 6 11 7 12 1 12 2 14 1 14 2 Physical Layout of HERMES 0 2002000002 eee eee 21 Allocation options in Configure 2 CL m rn nn 42 Allocation options in Configure 44 HERMES Spectrograph Control Window ooo e a 54 Automatic Focus Window a oaoa a a 55 Focus Mech Window oaa aa nn 55 Confirm changes to focus values nn nn 55 COD Control Window 4 4102 8 2a nb e ni an ban ani 64 CCD Control Window aoaaa 66 The ARC lamp selection window oo 67 The Flat field lamp selection Window 2 2 0000 eee eee ee 68 The 2dF main window upon start up After initialising the system will show the status as Available in green aa a 69 The HERMES Trust Prompt 2 on nn nn 70 2dF internet power switch window 2 22mm nn rail The three windows of the Focal Plane Imager Control 74 Textbook example of a focus run with the FPI camera o o TI 2dF Positioner Control window 84 2dF Telescope Control window 86 List of Tables 3 1 HERMES Readout Modes 3 2 HERMES Calibration exposure times 00000002 eee 6 1 2dF Distortion Model F
94. uration is needed rapidly Note the original Oxford configuration algorithm which can be used instead of the annealing by running the configureTrad command will be far quicker 41 hd Allocation B Set Allocation Parameters and Hit OK to Allocate Quick Annealing Standard Thorough 4 Weight Close Pairs ThetaMin arcsec lo ThetaMax arcsec 60 4 CrossBeamSwitching never Straighten Fibres moderate heavy Collision matrix filename collision matrix W Enforce sky quota M Weight peripheral fiducial targets 4 Weight fiducial target pairs Number of background threads to use jo W On the fly collision calculation Number of AAOmega fibres to assign to sky 25 Figure 6 1 Allocation options in Configure Number of Sky fibres The indicated number of sky fibres will be assigned but see the note above on enforcing the sky fibre quota 6 2 4 Additional Expert allocation options These options can only be accessed via the Expert user mode which one activates via the toggle setting in the Options menu These settings are generally for support astronomers and expert users These are illustrated in Figure 6 2 Fibre clearance Button clearance and pivot angle These options are mainly for the 2dF support staff If you do not know what they are used for then you should not adjust them Note that the 2dF robot has safe values HARD WIRED into the system and so a configuration
95. use the sparse sampling set the seed for the random number generator and then set the percentage of allocations to sample Using only 10 will result in a very quick configuration but most likely a poor yield Using 80 seems to give a significant improvement in speed without an obvious detrimental effects on the yield Note this mode is still underdevelopment and it s effects are poorly understood at this time 6 3 What is needed for observing In order to achieve a wide field of view and good image quality over that entire field of view the 2dF prime focus corrector suffers from Chromatics Variation in Distortion CVD This means that while the Atmospheric Distortion Corrector ADC accounts for the effect of the atmosphere on your target object s white light apparent positions the prime focus corrector moves your target on the field plate as a function of wavelength The effects can be quite large up to 2 arcsec in the worst case when considered over the full wavelength range accessible to 2dF and over the full 2 degree field 2dF knows about CVD and so you must specify for what wavelength you want 2dF to put the fibres in the correct position This must be the compromise which best suits your program goals 43 Allocation Set Allocation Parameters and Hit OK to Allocate Fibre clearance 400 to 40000 microns Button clearance 400 to 40000 microns Max non radial pivot angle 0 00 to 14 32 degrees Annealing ThetaMin a
96. ut to ensure that half of the fibres e g 50 150 250 and 350 go to position A guide stars while the other half e g 100 200 300 and 400 go to position B guide stars There is no requirement that these stars be the same set in the A and B positions Number of background threads to use The calculation of the fibre collision matrix is very CPU intensive On a modern multi CPU machine Configure can hijack all of the available CPUs and run a number of background threads this vastly reduces the allocation time For a single CPU machine there is nothing to gain here On the fly collision calculation By default the the collision matrix is calculated in full in advance of the annealing this is the way Configure v7 4 operated when SAconfigure was first introduced An alternative is to calculate it on the fly This ensures that A configu ration is achieved as quickly as possible This configuration will be HIGHLY sub optimal The longer the process is allowed to run the greater the region of parameter space that is investigate and the the better configuration will be In the limit of the annealing process the two approaches will produce identically good configurations and will take identically long to reach this point There is therefore often little point in doing the calculations on the fly In fact this option may allow inexperienced inpatient users to produce sub optimal configurations It can however be used in cases where a pretty good config
97. wever the user should exercise some restraint when using the available levels Using all of the available priorities to derive a complex priority selection function will almost always yield very limited returns at the expense of usability 5 2 Guide Stars Guide stars are crucial to the success of your observations so pay careful attention here Guide stars not only are used to guide the telescope but also determine the field plate rotation and set the relative position of the science fibres on the sky Poor choices may mean that no light falls on science fibres e 2dF instruments have eight guide bundles available All eight should be allocated wherever possible This will reguire 20 30 or more candidate guide stars well distributed across the field plate to ensure all guide fibres can be allocated and prevent guide star selection compromising science fibre placement e Guide stars as bright as 8th magnitude in V can be used but typically stars in the range 12 13 5 are best Fields closer to the moon will require brighter stars Stars fainter than 14th magnitude in V are typically too faint e The range in guide star magnitude should be made as small as possible to that all guide bundles are evenly illuminated In practice less than 1 mag is a good range and 0 5 mag is best e Guide stars MUST be on the same astrometric system as your targets Otherwise you will likely place your science fibres on blank sky e Be aware of proper motio
98. which is outside these bounds will be flagged as INVALID at configuration time These settings should only be used to restrict the values to tighter constraints for reasons that are beyond the scope of this web page Random Seed and Percentage of allocations sampled If one needs to configure more quickly e g if the field is pathologically complex usually centrally condensed or with heavily clus tered targets and one cannot alter fibre allocations as described above and on the complex 42 configurations page then it is possible to sparse sample the collision matrix and speed up the process The details of this option are beyond the scope of this guide and should be discussed with your support astronomer The principle is for such configurations that the slow speed is caused by the large number of rather similar configuration that are available in essence many objects could be configured with many different fibres without changing the basic properties of the configuration The sparse sampling reduces the number of available allocations for these heavily oversampled objects but does not remove the object from the possible allocations Note that at this time the effect of this sparse sampling on properties such as spatial clustering is unknown In most cases a better construction of the fid file with serious thought given the the true requirements of the project is more appropriate than using sparse sampling on a poorly defined input file To
99. with help dialogue to select the mode where unused fibres will be left in the field unless they are in the way of the future configuration Remember to unset the flag after doing the configuration it also automatically resets on the next restart of 2dF 14 2 Acquiring a New Field Acquiring the first field of the evening and slewing to a new field is a complex task 1 If changing fields check that all required calibrations have been taken with the current field before tumbling to the new field 2 In the Telescope Control window select the source for the next observing positions typically Config Plate File Clicking Load Position from File should update the position boxes on the left hand side of the window 3 Check with the night assistant that it is safe to slew the telescope then click Commence Slew and Track in the same window 4 While the telescope slews exchange the field plates using the Tumble button in the Posi tioner Control window 5 Once the new plate is in position and the spectrograph slit exchange has completed take the required calibration frames usually an arc and a flat While these frames read out there is generally time to check the seeing and centre the field using the FPI camera necessary to go back to configure and either de allocate the offending fibres or re do the allocation Confirm that configure is using the current distortion model In general it is safe to take calibrations while slewi
100. x A box can be defined for centroiding operations by Shift left dragging a box in the FPI SkyCat window CCD Readout Window The CCD readout window can be changed to e g get a larger field or decrease the readout time using the Image Set Window command in the menu It is generally advisable to centre the window 74 12 2 Checking the seeing With a star in the FPI field of view it is possible to measure the seeing or more exactly the FWHM of whatever object is selected With care the seeing can be checked during an AAOmega readout as it takes less than 60 seconds 1 Move the FPI to a star of suitable brightness in the field by selecting one from the Select Object window and clicking Goto RA Dec Alternately one can search for a star by jogging the FPI around the field 2 By default the software uses the full CCD window to measure the FWHM Especially in crowded fields it is necessary to draw a selection box which only includes the object of interest Shift left drag within the image to create a selection box Typically the box needs to be at least a few times the objects FWHM to be useful 3 With the Compute Centroid box checked take an image of at least 1 second to average out the seeing The FWHM of the star will be displayed in the scrolling message area of the FPI Main Window 12 3 Acquiring Fields with the FPI The FPI can also be used to acquire an object place it s light accurately on a fibre button This is

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