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HAWK-I User Manual
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1. 33 F 4 2 OB Requirements and Finding Charts 33 KAS Observing Modes 34 F44 Calibration Pla AA AA eee oe ee ade tand orau RS 34 F45 Filo Fles Mame soced oca mdd amata niei e 24 BEERS 34 E B Template Guide 34 F 5 1 Acquisition HAWKI_img_acq FastPhot 34 F 5 2 Science template HAWKI_img_obs_FastPhot 36 F 5 3 Calibration templates HAWKI_img_cal_DarksFastPhot 37 HAWK I User Manual Issue 88 1 1 Introduction 1 1 Scope of this document The HAWK I user manual provides the information required for the proposal preparation phase 1 the phase 2 observation preparation and the observation phase The instrument has started regular operations in period 81 We welcome any comments and sug gestions on the manual these should be addressed to our user support group at usd help eso org 1 2 Structure of this document The document is structured in 2 parts Part 1 1 takes you step by step through the essentials writing your proposal in phase 1 preparing your observations in phase 2 conducting your obser vations at the telescope and reducing your data Part 2 II contains collected useful reference material 1 3 Glossary 1 4 Abbreviations and Acronyms DMO ESO ETC FC FoV FWHM HAWK I NIR OB P2PP PSF QC RTC RTD SM TIO USD VLT VM Data Management and Op
2. Organisation Europ ene pour des Recherches Astronomiques dans Hemisphere Austral A Europ ische Organisation f r astronomische Forschung in der s dlichen Hemisphare ES EUROPEAN SOUTHERN OBSERVATORY o A ESO European Southern Observatory Karl Schwarzschild Str 2 D 85748 Garching bei M nchen Very Large Telescope HAW K I User Manual Doc No VLT MAN ESO 14800 3486 Issue 89 01 September 2011 Giovanni Carraro and the HAWK I IOT Ed EES C Dumas AP scans Sa nek Se Dee ee hk Dyin yee ete es Name Date Signature A Kaufer S EU AA KUFUZU KUTUA SANGA KUU Rae E HAWK I User Manual Issue 88 Change Record Issue Rev Date Section Parag Reason Initiation Documents Remarks affected Issue 1 25 May 2007 all First release for PAE Issue 81 31 August 2007 prepared for CfP P81 6 Dec 2007 all update after end of commissionnings Issue 82 06 March 2008 P82 Phase version bump Bug in over head table corrected Minor changes to introduction Issue 82 1 06 March 2008 minor bug Issue 82 2 06 March 2008 Added warning about sky subtraction Issue 83 0 01 Sep 2008 P83 Phase 1 cal plan Issue 83 1 27 Nov 2008 P83 addenda for the IP83 release Issue 84 0 29 May 2009 P84 addenda New read out mode and persistence study Change of offset scheme Issue 84 1 27 Jun 2009 P84 addenda cleaning and Phase II Issue 85 0 09 Dec 2009 P85 Phase and Il Issue 85 1 28 Feb 2010 Fast P
3. Figure 1 Pop up window at the start of an example template it provides a quick check of your offset pattern In the above example Fig 1 7 offsets are requested and the way the are performed is shown in Fig 2 The sequence of offset will be 10 10 90 10 100 200 100 200 300 420 and 580 10 4 5 Instrument and telescope overheads The telescope and instrument overheads are summarized below HAWK I User Manual Issue 88 13 ll Telescope offsets J Delta Alpha Quit Figure 2 Offset execution along the template Hardware Item Action Time minutes Paranal telescopes Preset 6 HAWK I Acquisition Ae HAWK Initial instrument setup for ACQ only 1 HAWK I Telescope Offset small 0 15 HAWK I Telescope Offset large gt 90 2 0 HAWK Readout per DIT 0 03 HAWK I After exposure per exposure 0 13 HAWK Filter change 0 35 The instrument set up is usually absorbed in the telescope preset for a simple preset In the case of MoveToPixel the exact integration time is dependent on the number of images one needs to take at least 2 and of course the corresponding integration time For 3 images of Detector Integration Time DIT 2 NDIT 1 the overhead is 1 5min 4 6 Recommended DIT NDIT and Object Sky pattern For DITs longer than 120sec the SM user has to use one of the following DIT 150 180 240 300 600 and 900sec Table 3 lists the contrib
4. All calibrations taken within the context of the calibration plan are pipeline processed and quality controlled by the Quality Control group at ESO Garching The raw science and calibration data are available to the PI only through the ESO archive Master calibrations and science pipeline products are no longer available More information about the HAWK I quality control can be found under http www eso org qc index_hawki html The time evolution of the most important instrument parameters like DARK current detector characteristics photometric zero points and others can be followed via the continuously updated trending plots available on the HAWK I QC webpages HAWK I User Manual Issue 88 28 E The HAWK I pipeline We refer to the pipeline manual for a full description on the HAWK I pipeline This section provides only a very brief overview of what to expect from the pipeline The pipeline full documentation is available at http www eso org sci data processing software pipeli The planned data reduction recipes included in this delivery will be e hawki_img_dark The dark recipe produces master dark and bad pixel map e hawki img flat The flat field recipe produces a master flat a bad pixel map a statistics table the fit error image e hawki img zpoint This recipe provides the zero points for the UKIRT selected standards e hawki_img_detlin This recipe determines the detector linearity polynomial coefficients com putation
5. A note of caution as all current infrared arrays the HAWK I detectors suffer of persistence at the level of 107 1074 depending on how badly the pixels were saturated that decays slowly over minutes about 5min for the maximum tolerated saturation level in SM This might leave artifacts reflecting the dither pattern around saturated stars 2 2 Photometry with HAWK I As you will have noticed acquiring a single star per night does not allow to carry out high precision photometry but rather to monitor the instrument performance and make a rough evaluation of the quality of the night HAWK I User Manual Issue 88 5 2 2 1 Two ways to get reasonable photometry If good photometry is your goal you should go for one of the following options e Ask for special calibrations Take into account as early as phase 1 i e in your proposal the fact that you want to observe more and other standard fields than the ones foreseen in the calibration plan In your README file you can then explain that you want your specified standard field observed e g before and after your science OB You can also specify that you want illumination maps for your filters close in time to your observations and or specify as special calibrations your own illumination maps e f a photometric calibration to 0 05 0 1 magnitude is enough for your program consider that the HAWK I field is large and that by experience you will have 10 100 stars from the 2MASS cat
6. Can you bring your own filters Possibly HAWK I hosts large 105mm7 i e expensive filters and was designed to have an easy access to the filter wheel However to exchange filters the instrument needs to be warmed up which usually only happens once per year Thus in exceptional cases i e for very particular scientific program user supplied filters can be installed in HAWK I within the operational constraints of the observatory Please make sure to contact paranal eso org before buying your filters 2 1 3 Limiting magnitudes Limiting magnitudes are of course very much dependent on the observing conditions The exposure time calculator ETC is reasonably well calibrated and we encourage you to use it In order to give you a rough idea of the performance to be expected we list here the limiting magnitudes S N 5 for a point source in 3600s integration on source under average conditions 0 8 seeing 1 2 airmass HAWK I User Manual Issue 88 4 Filter Limiting mag Limiting mag Saturation limit Vega AB in 2 sec J 23 9 24 8 10 0 H 22 9 23 9 10 3 Kg 22 3 24 2 9 2 assumed 0 8 seeing For more detailed exposure time calculation in particular for narrow band filters please use the exposure time calculator Due to persistence effect of the detector in service mode no observation will be accepted for fields containing objects brighter than K 8 1 H 9 1 amp J 8 8 i e 5 times the saturation l
7. 23 CHIP 1 CHIP 2 T T T Te T A r ge 8 aa a 4 ye L J L A C amp A L 4 xe E 6p ot x A DT L J A A 4 LA A A A A A a4 A aa A E be I igerri 5 5 10 NDIT NDIT CHIP 3 CHIP 4 mT T at TT el LA A LA A A S 0 6 L J A L J S io a i R 7 E a E 8 K A F A A S Sun oA ig d a J O A A sd L E H L 4 A a a L ol A A A A a le A 4 1 0 4 A z a A A bo L 134 Figure 9 Trend of dark with NDIT in the 4 detectors x ze e z yi KAA mwa P gt x S D x N Y s Es S C D _CHIP 4 lt KH R WA AA LC E 3 if a ole fie PE K of Si SEI L oo d E M D D SE S ae D ef S L D lt a d a is GES v S z 1 V D SE 4 fee r ee LE L S GEN GR F WA W fe gt E Wa Y E R TR z Rig F Ee S SE tae aa ns air e 4 E ss x wel R s E m RRS re CRIP 1h YA ee x Y CHIP Z wy a er s E ee E RE OR a OR be yes ate SG v x EE z Z SE WA 2 zA S G Z E L E d ya eee 3 3 Ae Ka U Ke re DN D we Bre o S R Se ae a ey E 2 s x Z TA RES CH D d 3 X i ee Sh SW on 3 e ee MER b P A EE G T YA R E AZ Figure 10 The field around the z 2 7 quasar B0002 422 as seen in the 4 HAWK I quadrants HAWK I User Manual Issue 88 24 16 CHIP 1 14 CHIP 2 A Se CHIP 3 3 10F CHIP 4 oO 3 8 Coadded stack ap E B 6 z 03 uM 15 le L 8 I9 MAG_APER D 1 8 ZP 25 Figure 11 Number
8. DET WIN NY define the detector windowing As in the science template they are used to window the detectors but unlike the science template they are explicitly defineable and accessible by the users The parameter is not available in the calibration templates All the calibration are taken as reconstructed images in other words DET BURST MODE is internally always set to False Readout mode is set in the template implicitly to NonDest because for now this is the only one for which the new windowing is implemented The hardware windowing is set to true The store in cube option is set to true
9. H J 500 E 4 1 ay L j o bee KUKUA KAA g a il 0 500 1000 1500 2000 0 500 1000 1500 2000 X 2000 PITT 2000 PTT 1500 L 4 1500 L 4 L oi J L Q2 1000F chip 66 E 1000 f chip 78 500 F 4 500 E 4 posi tir tisiitiiii I nl 0 500 1000 1500 2000 0 500 1000 1500 2000 Note that quadrant 1 2 3 4 are usually but not necessarily stored in extensions 1 2 4 3 of the HAWK I FITS file Indeed FITS convention forbids to identify extensions by their location in the file Instead look for the FITS keyword EXTNAME in each extension and verify that you are handling the quadrant that you expect eg EXTNAME CHIP1 INT1 The characteristics of the four detectors are listed below Detector Parameter Ql Q2 Q3 Q4 Detector Chip 66 78 79 88 Operating Temperature 75K controlled to 1mK Gain e7 ADU 1 705 1 870 1 735 2 110 Dark current at 75 K e s between 0 10 and 0 15 Minimum DIT 1 6762 s Read noise NDR 5 to 12 e7 Linear range 1 60 000 e 30 000 ADUs Saturation level between 40 000 and 50 000 ADUs DET SATLEVEL 25000 1 The noise in Non Destructive Read NDR depends on the DIT the detector is read continuously every 1 6762s i e the longer the DIT the more reads are possible and the lower the RON For the minimum DIT 1 6762s the RON is 12e7 for DIT 10s the RON is 8e7 and for DIT gt 15s the RON remains stable at 5 E Figure 6 represents the quantum efficiency curve for each of the dete
10. The influence of the Moon 2 266215 482944444 44646464 4 46 4 4 4 Orientation offset conventions and definitions 4 5 Instrument and telescope overheads 2 a a 4 6 Recommended DIT NDIT and Object Sky pattern Reference Material KA enerne N Gn On Om Om Om Ln A P GO GO KA KA KN WO CO CO CO CO HAWK I User Manual Issue 88 v A The HAWK I filters 16 B The HAWK I detectors 19 B 1 Threshold limited integration 20 B 2 Detectors structures and features 20 B 3 Detectors relative sentisivity 21 C The HAWK I Field of View 25 C 1 Relative position of the four quadrants 25 C 1 1 Center of Rotation and Centre of Pointing 25 C 2 Vignetting of the field of view 26 D The HAWK I calibration plan 27 D 1 Do you need special calibrations 27 D 2 The HAWK I standard calibrations in a nutshell 27 D3 Quality Controls se soeone Cae a EMS Ee ap Cee ew R 27 E The HAWK I pipeline 29 F HAWK I Burst and Fast Jitter Modes 30 Pal The Mode in Nutshell 30 Fa Description o c seose sop ed AA AA L e SE ed WA 30 FS Timing Information c e bocen ase Soe won HE bee ea a d a a 33 FA Preparation and Observation 33 Fal OB Naming Convention
11. and time from the first frame A sequence of frames in the K band was obtained when the target was near the zenith and the pupil was rotating by 2 45 degrees minute Being the VLT an alt azimuth telescope the image rotates with respect to the pupil This is noticed as a rotation of the difraction spikes seeing around bright stars The sky subtraction error is larger when the pupil rotation angle between the two images is largest HAWK I User Manual Issue 88 15 Figure 3 The annotation indicate the difference in pupil angle between the two frames being subtracted and the difference in start time between the two exposures HAWK I User Manual Issue 88 16 Part Il Reference Material A The HAWK I filters The 10 filters in HAWK I are listed in Table 4 The filter curves as ascii tables can be retrieved from the hawki instrument page Note in particular that the Y band filter leaks and transmits 0 015 of the light between 2300 and 2500 nm All other filters have no leaks at the lt 0 01 level Table 4 HAWK I filter summary Filter name central cut on cut off width tansmission comments wavelength nm 50 nm 50 nm nm Kal Y 1021 970 1071 101 92 LEAKS 0 015 at 2300 2500 nm J 1258 1181 1335 154 88 H 1620 1476 1765 289 95 K 2146 1984 2308 324 82 CH 1575 1519 1631 112 90 Bry 2165 2150 2181 30 77 H 2124 2109 2139 30 80 NB1060 1061 1057 1066 9 70 NB1190 1186 1180 1
12. counts as a function of aperture magnitude for the four HAWK I chips The magnitudes as plotted adopt an arbitrary zeropoint of 25 plus the relative zeropoint offsets as monitored for the J filter 0 14 0 03 0 23 mag for chips 2 4 relative to chip 1 The limiting magnitudes i e the location of the turnover in the number counts of the four chips are essentially identical within the measurement precision of this exercise lt 10 Also shown are the number counts for a deep coadded stack of the four rotated and aligned jitter sequences We use this deep image to assess the number of spurious sources detected on each chip objects matched from the single chip image to the deeper image are considered to be real while objects that only appear on the single chip images are considered spurious The number of spurious detections is negligible for chips 1 3 and 4 though for chip 2 it reaches 20 around the limiting magnitude HAWK I User Manual Issue 88 25 C The HAWK I Field of View C 1 Relative position of the four quadrants The four quadrants are very well aligned with respect to each other Yet small misalignments exist They are sketched below Q4 chip 88 chip 79 8 0 03 8 0 04 Q2 Q1 hip 78 chip 66 8 0 130 Quadrants 2 3 4 are tilted with respect to quadrant 1 by 0 13 0 04 0 03 degrees respectively Accordingly the size of the gaps changes along the quadrant edges The default orientati
13. detectors and the gaps projected on the sky in arcsec are also given The binaries gen erated from quadrants 1 2 3 and 4 are usually but not always stored in fits extensions 1 2 4 and 3 Arrows indicate the direction in which the parameters DET WIN STARTX DET WIN STARTY DET WIN NX and DET WIN NY increase Note that the param eter DET WIN STARTX defines the starting point of the window counted from the beginning of each detector stripe not from the beginning of the detector Note that all these parameters are defined in pixels although this figure is plotted in arcsec Four different sets of windows are shown in violet yellow solid and dashed black lines HAWK I User Manual Issue 88 32 require action on the part of the user F 3 Timing Information The minimum DIT and the execution time for some parameter combinations are listed in Table 5 These values may change quickly for the latest information please check the HAWK I web pages Table 5 Timing Parameters for NDIT x DIT 1000 x 1 sec 1000 sec of integration The 32 and 2 multiplication factors are given to remind the user that the NX and NY parameters are the total width of the detector windows across the entire set of stripes The readout mode is NonDest STARTX NX STARTY NY MINDIT Exec Overhead Overhead sec Time sec per DIT sec sec 1 64 128 64 0 0260 1174 174 0 174 1 64 128 128 0 0517 1199 199 0 199 1 128 128 64 0 0506 1198 198 0 198 1 128 128 128 0 100
14. features More of these can be seen in Fig 8 on chip 88 Both features are stable and removed completely by simple data reduction no extra step needed HAWK I User Manual Issue 88 21 Figure 7 Typical raw HAWK I dark frame DIT 300sec 3 Detector glow which is visible for long DITs but is removed by e g sky subtraction 4 The darker area visible in Fig 8 corresponds to the shadow of the baffling between the detectors 5 Emitting structure whose intensity grows with the integration time It is however fully removed by classical data reduction 6 Q2 chip 78 suffers from radioactive effects see Fig 10 below 7 Q4 chip 88 dark median has been found to be larger than the other detectors and to increase with NDIT see Fig 9 Thanks to Sylvain Guieu for detecting this B 3 Detectors relative sentisivity We undertook a program to assess the relative sensitivities of the four HAWK I chips using ob servations of the high galactic latitude field around the z 2 7 quasar BO002 422 at RA 00 04 45 Dec 41 56 41 taken during technical time The observations consist of four sets of 11 x 300 sec AutoJitter sequences in the NB1060 filter The four sequences are rotated by 90 degrees in order that a given position on the sky is observed by each of the four chips of the HAWK I detector The jitter sequences are reduced following the standard two pass background subtraction workflow de scribed in the HAWK I pipeline manual Obje
15. no file has to be attached except for the finding chart all other entries are typed 3 1 2 Observing Blocks OBs As an experienced ESO user it will come as no surprise to you that any HAWK I science OB should contain one acquisition template followed by a number of science templates If this did surprise you you may need to get back to the basics 3 1 3 Templates The HAWK I templates are described in detail in the template reference guide available through the instrument web pages A brief overview is given below If you are familiar with the ISAAC SW imaging or NACO imaging templates these will look very familiar to you and cover essentially the same functionalities The acquisition and science templates are listed in Table 1 Two forms of acquisition exist a simple preset when a crude accuracy of a couple of arcsec is enough and the possibility to intearctively place the target in a given position on the detector The science templates provide four forms of obtaining sky images small jitter patterns for un crowded fields random sky offsets for extended or crowded fields when the off position needs to be acquired far from the target field fixed sky offsets when random sky offsets are not suited and fi nally the possibility to define an arbitrary offset pattern when the standard strategies are not suited HAWK I User Manual Issue 88 9 For Rapid Response Mode we offer two acquisition templates They are exactly th
16. position The astrometry and flexure templates are needed to compute the distortion map the plate scale and relative positions of the detectors and to quantify possible flexures Three further templates are used to characterize the detector to determine the best telescope focus and to measure the reproducibility of the filter wheel positioning Table 2 Calibration and technical HAWK I templates calibration templates functionality comment HAWKI_img_cal_Darks series of darks HAWKI_img_acq_TwPreset acquisition for flat field HAWKI_img_cal_TwFlats imaging twilight flat field HAWKI_img_cal_SkyFlats imaging sky flat field HAWKI_img cal_StandardStar imaging of standard field available to the SM user technical templates HAWKI img tec IlluFrame imaging of illumination field HAWKI_img_tec_Astrometry imaging of astrometric field HAWKI_img_ tec_Flexure measuring instrument flexure center of rotation HAWKI_img_tec_DetLin detector test monitoring HAWKI_img tec_Focus telescope focus determination HAWKI_img_tec_FilterWheel filter wheel positioning accuracy 3 2 Finding Charts and README Files In addition to the general instructions on finding charts FC and README files that are available at http www eso org observing p2pp the following HAWK I specifics are recommended e The FoV of all FCs must be 10 by 10 in size with a clear indication of the field orientation HAWK I User Manual Issue 88 10 e Ideally
17. total observing time will be much larger e The S N is computed over various areas as a function of the source geometry point source extended source surface brightness Check carefully what was done in your case Most of the other ETC parameters should be self explaining and or well explained in the online help of the ETC 2 4 Proposal Form HAWK I allows only 1 set up direct Imaging Please indicate which filters in particular narrow band filters you intend to use This will allow us to optimize their calibration during the semester INSconfig HAWK I Imaging provide HERE list of filters s Y J H K NB1060 NB1190 NB2090 H2 BrG CH4 T 2 5 Overheads and Calibration Plan When applying for HAWK I do not forget to take into account all the overheads when computing the required time HAWK I User Manual Issue 88 7 e Make sure that you compute the exposure time including on sky time not only on source if your observing strategy requires it e Verify in the call for proposal that you have taken into account all listed overheads which can also be found in Sect 4 5 To do so you can either refer to Sect 4 5 or simulate the detailed breakdown of your program in terms of its constituent Observing Blocks OBs using the P2PP tutorial manual account see Sect 1 4 of the P2PP User Manual available at The Execution Time Report option offered by P2PP provides an accurate estimate of the time needed for the execution of each OB
18. 192 12 75 NB2090 2095 2085 2105 20 81 Optical ghosts out of focus images showing the M2 and telescope spiders have been rarely found only with the NB1060 Lya at z 7 7 amp NB1190 Lya at z 8 7 filters As illustrated in Fig 4 the ghost images are 153 pixels in diameter and offset from the central star in the same direction however the latter varies with each quadrant and is not symmetric to the centre of the moisac The total integrated intensities of the ghosts are in both cases 2 but their surface brightnesses are a factor 1074 of the peak brightness in the stellar PSF The figure 5 summarizes the HAWK I filters graphically HAWK I User Manual Issue 88 17 Figure 4 Smoothed enhanced images of the optical ghosts visible in the four quadrants for the NB1060 left amp NB1190 right filters HAWK I User Manual Issue 88 18 100 L Y J H K 80 L 4 an li CH SS ent H gt 5 L Bry gt oO e az K 0 L NB NB1190 NBRO90 4 a 40 L UI 20 L 4 0 K 1 1 L 1 1000 1500 2000 wavelength nm Figure 5 HAWK I Filters Black broad band filters Y J H Ks Green cosmological filters NB1060 NB1190 NB2090 Red CH4 H2 Blue Bry HAWK I User Manual Issue 88 19 B The HAWK I detectors The naming convention for the four detectors is the following 2000 PTT 2000 BT 1500 F 4 1500 E 4 L Q4 b L Q3 1000 8 chip 88 E 0094 chip 79 500
19. 8 1248 248 0 248 1 128 128 256 0 2013 1349 349 0 349 1 128 1792 128 0 1037 1251 251 0 251 1 32 128 32 0 0070 1155 155 0 155 F 4 Preparation and Observation F 4 1 OB Naming Convention Following the common convention for the fast modes e FastJitter OBs BURST F should start with the prefix FAST in their name e Burst OBs BURST T which does not make use of the EVENT keywords EVENT DATE 0 and EVENT TIME 0 should start with the prefix BURST in their name e Burst OBs BURST T which make use of the EVENT keywords EVENT DATE YYMMDD and EVENT TIME HHMMSS need to include the time at which the science template not the acquisition should start i e the UT time of the EVENT time minus half the total exposure time For example let us assume that you are exposing for 30 sec in total and lets assume that your event occurs at UT date YY MMDD and UT time HHMMSS then your OB name should include the following prefix BURSTUTYYMMDDHHMMss where SS SS 30 2 SS 15 F 4 2 OB Requirements and Finding Charts The Burst mode OBs are allowed to use the HAWKI_img_acq_Preset template This is necessary for example for Lunar occultations where a large number of events can be followed in a raw with small intervals in between The OBs making use of this acquisition template do not need HAWK I User Manual Issue 88 33 an attached finding chart It will be responsibility of the user to double check his her coordinates since this is in e
20. NX and DET WIN NY are not accessible to the user from this template The parameter DET BURST MODE selected between Burst True and Fast Jitter False modes The parameters EVENT DATE and EVENT TIME define the time at which the ob servation has to be centered They are ignored if DE T BURST MODE is set to False They are also ignored if they are set to zero to streamline the usage of the Burst mode for non time critical observations i e for lucky imaging Readout mode is set to NonDest because for now this is the only one for which the new windowing is implemented The hardware windowing is set to true implicitely for the use The store in cube option is set to True The parameters BADAG and BADAO determine if the template checks and waits for guiding and active optics False check True no check F 5 3 Calibration templates HAWKI _img_cal_DarksFastPhot Twilight flats for this mode are obtained with the normal non windowing HAWKI_img_cal_TwFlats template making the dark current calibration template HAWKI_img_cal_DarksFastPhot the only unique calibration template for the fast mode It is similar to the usual dark current template HAWK I_img_cal_Darks with the execution of the hardware windowing and the storage of the data in cubes The parameters for filter DIT and NDIT are lists allowing to obtain multiple darks in one go Specific details The new windowing parameters DET WIN STARTX DET WIN STARTY DET WIN NX and
21. WK I User Manual Issue 88 6 http www eso org observing etc it returns a good estimation of the integration time on source needed in order to achieve a given S N as a function of atmospheric conditions A few words about various input variables that might not be quite standard also read the online help provided on the ETC page e the parameters to be provided for the input target are standard The input magnitude can be specified for a point source for an extended source in which case we compute an integration over the surface defined by the input diameter or as surface brightness in which case we compute values per pixel e g 106106 mas e Results are given as exposure time to achieve a given S N or as S N achieved in a given exposure time In both cases you are requested to input a typical DIT which for broad band filters will be short 10 to 30s but for narrow band filters could be long exposures between 60 and 300s before being sky background limited e Do not hesitate to make use of the many graphical outputs In particular for checking your target line and the sky lines in the NB filters The screen output from the ETC will include the input parameters together with the calculated performance estimates Here some additional notes about the ETC output values e The integration time is given on source depending on your technique to obtain sky mea surements jitter or offsets and accounting for overheads the
22. alog in your field These are typically cataloged with a photometry good to lt 0 1 mag and would allow to deter mine the zero point on your image to 0 05 mag using these local secondary standards Extinction coefficients would automatically be taken into account They are measured on a mothly basis Besides we remind that colour terms for HAWK I are small 0 1x J K Check with Skycat or Gaia ahead of time whether good non saturated 2MASS stars are present in your science field Skycat is available under http archive eso org skycat Gaia is part of the starlink project http starlink jach hawaii edu 2 2 2 Consider the 2MASS calibration fields The 2MASS mission used a number of calibration fields for the survey Details are given at http www ipac caltech edu 2mass releases allsky doc seca4_1 html In particular the sect II 2 http www ipac caltech edu 2mass releases allsky doc sec3_2d html provides a list of fields touch stone fields that you could use as photometric fields in order to calibrate your observations 2 2 3 HAWK I extinction coefficients We measured HAWK I extinction coefficient for the broad band filters as a result of a year moni toring The results are J 0 043 0 005 H 0 031 0 005 K 0 068 0 009 Y 0 021 0 007 We plan to keep monitoring these coefficients on a monthly basis according to the calibration plan 2 3 The Exposure Time Calculator The HAWK I ETC can be found at HA
23. amples of various detector window definitions For instance an increase of the parameter DET WIN STARTX would move the violet set of windows towards the yellow set if the other parameters are fixed Similarly an increase of the parameter DET WIN STARTY would move the violet set towards the solid black set The dashed black line set corresponds to DET WIN NX 128 128x16 stripes x2 detectors 4096 px in total along the X direction that defines contiguous windows see bellow The minimum DIT depends on both the size and the location of the detector windows For example DET WIN STARTX 48 DET WIN STARTY 1075 DET WIN NX 32 and DET WIN NY 32 corresponding to windows on the stripes with sizes of 3232 px 3 4x3 4 arcsec gives MINDIT 4millisec An interesting special case is to define contiguous regions i e the windows on the individual stripes are as wide as the stripes themselves so there are no gaps along the X axis one has to use fro example DET WIN STARTX 1 DET WIN STARTY 48 DET WIN N X 128 and DET WIN NY 32 corresponding to windows on the stripes with sizes of 128 x 32 px 13 6x3 4 arcsec gives MINDIT 20 millisec Note that the stripes are 128 px wide so this is indeed a contiguous region on each of the detectors with size 2048 x32 px 217 7x3 4 arcsec One should try to use as big windows as the requirements for the MINDIT and for lowering the overheads allow because the larger windows greatly help with the target acquisition an
24. as well as the error on the fit e hawki_img_illum The illumination map of the detectors is obtained by observing a bright photometric standard consecutively at all predefined positions over a grid e hawki_img_jitter All science data resulting from the jitter and generic offset templates The four quadrants are combined separately The four combined products are eventually stitched together The online reduction pipeline working on Paranal will not provide this stitched image if min offset lt 1500 or max offset gt 1500 Besides utilities will be provided to make it easier for the users to reduce the data by hand step by step This utilities list is not finalised yet but will contain among others e hawki_util_distortion Apply the distortion correction e hawki_util_stitch Stiches 4 quadrant images together e hawki_util_stdstars Generates the standard stars catalog from ascii files e hawki_util_gendist Generates the distortion map used for the distortion correction HAWK I User Manual Issue 88 29 F HAWK I Burst and Fast Jitter Modes F 1 The Mode in Nutshell This section describes a mode for high cadence and high time resolution observations with HAWK l the fraction of time spent integrating is typically 80 of the execution time and the minimum DIT is in the range 0 001 0 1 sec This is achieved by windowed down the detectors to speed up the observations in other words to shorten the minimum DIT and to decrease t
25. ation on the sky or the Detector offsets 1 and 2 refer to the detector X and Y axis respectively For jitter pattern and small offset it is more intuitive to use the detector coordinates as you probably want to move the target on the detector or place it on a different quadrant in which case do not forget the 15 gap The sky reference system is probably only useful when a fixed sky frame needs to be acquired with respect to the pointing For a position angle of 0 the reconstructed image on the RTD will show North up Y and East left X The positive position angle is defined from North to East Note that the templates use always offsets relative to the previous pointing not relative to the original position i e each offset is measured with respect to the actual pointing For example if you want to place a target in a series of four offsets in the center of each quadrant point to the star then perform the offsets 115 115 telescope moves to the lower left star appears in the upper right i e in Q3 230 0 0 230 230 0 Note that HAWK offers during execution a display that shows at the start of a template all the offsets to be performed see below It provides a quick visual check whether your pattern looks as expected see Fig 1 iA Telescope offsets 30 200 7 260 210 110 200 300 220 6 1004 lt 1 410 10 2 100 07 denen ennet aa Se Delta CH L
26. ctors HAWK I User Manual Issue 88 20 r Y i Wavelength micro Navelength micro T Figure 6 Quantum efficiency of the HAWK I detectors BI Threshold limited integration The normal mode of operation of the HAWK detectors defined a threshold by setting the keyword DET SATLEVEL All pixels which have absolute ADU values below this threshold are processed normally Once pixels illuminated by a bright star have absolute ADU values above the threshold the values are no longer used to calculate the slope of the regressional fit For these pixels only non destructive readouts having values below the threshold are taken into account The pixel values writen into the FITS file is the value extrapolated to the integration time DIT and is calculated from the slope using only readouts below the thershold The pixels that have been extrapolated can be identified because their values are above DET SATLEVEL B 2 Detectors structures and features We present some of HAWK I s detector features in two examples Figure 7 is a typical long gt 60s exposure Some features have been highlighted e 1 some black features on chip 66 amp 79 For both of them when light falls directly on these spots some diffraction structures can be seen as shown in the corresponding quadrants in Fig 7 e 2 On the left chip 88 there is an artefact on the detector s surface layer On the right chip 79 these are sort of doughnut shaped
27. cts have been detected with the SExtractor software courtesy of Gabriel Brammer including a 0 9 gaussian convolution kernel roughly matched to the average seeing measured from the reduced images Simple aperture photometry is measured within 1 8 diameter apertures The resulting number counts as a function of aperture magnitude observed by each chip are shown in Fig 11 As expected the coaddition of the four jitter sequences reaches a factor of 2 0 8 mag deeper than do the individual sequences The limiting magnitudes here taken to be the magnitude HAWK I User Manual Issue 88 22 Figure 8 Typical raw HAWK I twilight flat field Y Band where the number counts begin to decrease sharply and a proxy for the chip sensitivities are remarkably similar between the four chips We conclude that any sensitivity variations between the chips are within the 10 While they do not appear to affect the overall sensitivity the image artifacts on CHIP2 caused by radioactivity events see Fig 10 do result in an elevated number of spurious detections dashed lines in Fig 11 at faint magnitudes reaching 20 at the limiting magnitude for this chip The number of spurious detections in the other chips is negligible see Fig 11 This rate of spurious detections on CHIP2 should be considered as a conservative upper limit as it could likely be decreased by more careful optimization of the object detection parameters HAWK I User Manual Issue 88
28. d to the FITS file name F 5 Template Guide F 5 1 Acquisition HAWKI_img_acq_FastPhot The template is similar to the ISAACLW_img_acq_FastPhot The action sequence performed by the template includes 1 Preset the telescope set up the instrument no windowing at this stage the full field of view is shown on the RTD 2 Move to the sky position take a non windowed image ask the operator to save it in the RTD and to turn on the sky subtraction 3 Take a non windowed image of the field of view ask the operator if an adjustment is neces sary Note that the adjustment here includes both the telescope pointing and field of view orientation and the detector windowing parameters At this stage the operator is expected HAWK I User Manual Issue 88 34 T T T T T T T T FF Win FF NonWin1 FF Win FF NonWin2 FF NonWin1 FF NonWin2 Gaussian mean 1 sigma 0 02 log N ji MA AN M d 1 1 2 1 4 Ratio of different flat fields Figure 13 Histograms of the ratios between a windowed and two non windowed Ks twilight flats For comparison the ratio of the two non windowed flats and a Gaussian function is also shown HAWK I User Manual Issue 88 35 to press the draw button that draws on the RTD the windowing as defined in the acqui sition template The operator can modify it at any time from now on but has to redraw to have the latest version shown on the RTD 4 If the opera
29. d tolerate target drifts inaccurate coordinates and even give a larger margin for human error issues that require time to be addressed which may not be available when observing time critical events The data product is a fits file with four extensions each a cube for one of the four detector arrays Each slice of the cube is a tiled images of all windows spliced together i e without the gaps that may be present between the individual windows The Burst sub mode generates a single fits tile the FastJitt as many files as the number of the executed jitters The only readout mode for which the new mode is implemented currently is NonDest The new mode works only with hardware detector windowing The difference between the hardware and the other option the software windowing is that in the first case only specified portion of the detectors is read while in the second case the entire detector is read and the windowing is applied later by software means The hardware windowing is set explicitly in the templates and doesn t HAWK I User Manual Issue 88 31 ae DET WIN STARTKI DET WIN STARTEX1 400 EI D D 3 z 4 300 E Z r N K H Vi U J LU U ZB Z e 47 200 D H 100 S Ra ES A 0 G 100 200 300 400 X arcsec Figure 12 Definition of the windows The location of the four HAWK I detectors on the fo cal plane are shown as well as the 16 stripes in which each detector is being read The sizes of the
30. ding very critical for your program i e should we acquire more flats e g in your narrow band filters Would you like to achieve a photometry better than a few percent i e do you need photometric standards observe right before after your science frames Is the homogeneity of the photometry critical for your program i e should you ask for illumination frames close to your observations Is the astrometry critical i e should we acquire a full set of distortion and flexure maps around your run We would be more than happy to do all that for you if you tell us so i e if you mention it in phase 1 when submitting your proposal D 2 The HAWK I standard calibrations in a nutshell Here is what we do if we do not hear from you HAWK I Calibration Plan Calibration number frequency comments purpose Darks 10 exp DIT daily for DITxNDIT lt 120 Darks 5 exp DIT daily for DITxNDIT gt 120 Twilight Flat fields 1 set filter daily broad band filters best effort basis 1 set filter as needed for narrow band filters Zero points 1 set broad band filter daily UKIRT MKO or Persson std Colour terms 1 set monthly broad band filters only best effort basis Extinction coefficients 1 set monthly broad band filters only best effort basis Detector characteritics 1 set monthly RON dark current linearity Please do not hesitate to contact us usd help eso org if you have any questions D 3 Quality Control
31. e same as the normal acquisition template but with the string RRM appended to the name Table 1 Acquisition and science HAWK I templates acquisition templates functionality comment HAWKI_img_acq_Preset Simple telescope preset recommended HAWKI img acg MoveToPixel Interactive target acguisition HAWKI_img_acq_PresetRRM Simple telescope preset for RRM offered starting P82 HAWKI_img_acq_MoveToPixelRRM Interactive target acquisition for RRM offered starting P82 HAWKI_img_acq_FastPhot Acquisition for windowed mode science templates HAWKI_img_obs_AutoJitter imaging with jitter no offsets recommended for low density fields HAWKI_img_obs_AutoJitter0ffset imaging with jitter and random sky offsets recommended for extended objects HAWKI_img_obs_FixedSky0ffset imaging with jitter and fixed sky offsets when random sky is not suited HAWKI_img_obs_GenericOffset imaging with user defined offsets HAWKI_img_obs_FastPhot imaging with fast read out and windowing The calibration and technical templates are listed in Table 2 The only calibration template accessible to the SM user is the one to take standard stars The calibration templates are foreseen to acquire darks flat fields and simple standard star obser vations to calibrate the zero point The technical templates are used for the periodical characterization of the instrument The illu mination frames are used to determine the variation of the zero point as a function of detector
32. erations Division European Southern Observatory Exposure Time Calculator Finding Chart Field of View Full Width at Half Maximum High Acuity Wide field K band Imager Near InfraRed Observing Block Phase II Proposal Preparation Point Spread Function Quality Control Real Time Computer Real Time Display Service Mode Telescope and Instrument Operator User Support Department Very Large Telescope Visitor Mode HAWK I User Manual Issue 88 2 Part Observing with HAWK I from phase 1 to data reduction 2 PHASE 1 applying for observing time with HAWK I This section will help you to decide whether HAWK I is the right instrument for your scientific projects take you through a quick evaluation of the observing time needed and guide you through the particularities of HAWK I in the proposal form 2 1 Is HAWK I the right instrument for your project HAWK I does only one thing but does it well direct imaging in the NIR 0 97 to 2 31 um over a large field 7 5 x7 5 So far HAWK I has been successfully used to study the properties of medium redshift galaxy clusters see e g Lidman et al 2008 A amp A 489 981 outer solar system bodies Snodgrass et al 2010 A amp A 511 72 the very high redshift universe Castellano et al 2010 A amp A 511 20 and exo planets Gillone et al 2009 A amp A 506 359 The recent implementation of Fast Photometry see Appendix F is probably going to boost more activity in the exo plane
33. es of the telescope pointing FITS keywords TEL TARG ALPHA TEL TARG DELTA in all quadrants C 2 Vignetting of the field of view The Hawaii2RG detectors have 4 reference columns rows around each device which are not sensitive to light In addition due to necessary baffling in the all reflective optical design of HAWK I some vignetting at the edges of the field has turned out to be inevitable due to positioning tolerances of the light baffles The measured vignetting during commissioning on the sky is summarised in the following table Edge No of columns or rows vignetted gt 10 Maximum vignetting Y 1 14 Y 8 54 X 7 36 X 2 15 The last column represents the maximum extinction of a vignetted pixel i e the percentage of light absorbed in the pixel row or column with respect to the mean of the field Note although the Y edge vignetting is small in amplitude it extends to around 40 pixels at lt 10 HAWK I User Manual Issue 88 27 D The HAWK I calibration plan D 1 Do you need special calibrations The calibration plan defines the default calibrations obtained and archived for you by your friendly Paranal Science Operations team The calibration plan is what you can rely on without asking for any special calibrations Thus we strongly advise all the users to carefully think whether they will need additional calibrations and if so to request them right in phase 1 For example is flat fiel
34. evel This is really a generous lower limit brighter objects will produce persistence now more easily because of the larger minimum DIT 1 6762 secs Please check carefully your fields during Phase Il preparation 2 1 4 Instrument s performance We expect HAWK I to be used for plain imaging photometry and astrometry The image quality of HAWK I is excellent across the entire field of view Distortions are below 2 over the full 10 diagonal and the image quality has always been limited by the seeing our best recorded images had FWHM below 2 2 pix i e lt 0 23 in the Ks band The photometric accuracy and homogeneity that we measured across one quadrant is lt 5 as monitored on 2MASS calibration fields We expect that with an even more careful illumination correction and flat fielding about 3 absolute accuracy across the entire field will be achieved routinely when the calibration database is filled and stable Of course differential photometry can be pushed to a higher accuracy Note in particular that given the HAWK I field size between 10 and 100 useful 2MASS stars calibrated to 0 05 0 10 mag are usually present in the field Finally the relative astrometry across the entire field is auto calibrated on a monthly basis see HAWKI calibration plan using a sample of globular clusters as references The distortion map currently allows to recover relative position across the entire field with a precision of 1 arcsec
35. ffect a blind telescope pointing The typical accuracy of the VLT pointings is bellow 1 arcsec Remember that the windowing is defined in the specialized acquisition template it HAWKI_img_acq_FastPhot These parameters can not be modified with the HAWKI_img_acq_Preset template Therefore HAWKI_img_acq_FastPhot must be executed at least once and the windowing parameters should be kept the same during the entire sequence The usage of HAWKI_img_acq_Preset template is allowed only in Visitor mode and it is forbidden in Service For more details on the templates see Sec F 5 The finding chart requirements are the same as for the other VLT instruments FA 3 Observing Modes The Burst and FastJitter modes are offered both in Visitor and in Service modes However in the case of Lunar occultations only disappearances are offered in Service Visitor mode must be requested in the case of appearances F 4 4 Calibration Plan e Darks taken with the same windowing and readout mode the latter is valid only if and when other readout modes are offered e Twilight Flats non windowed and with the same filters as the science observations are offered the users only have to excise from them the relevant windows we compared windowed and non windowed Ks flats and found no significant difference Fig 13 F 4 5 FITS Files Names The file names for the fast mode should contain FAST for clarity The extentions SAMPLE and DIT are also appende
36. he overheads The burst mode is intended for applications that require short high time resolution observations i e lunar and KBO occultations transits of extrasolar planets etc The Fast Jitter mode is intended for observations of extremely bright objects that require short DITs to avoid saturation and small overheads to increase the efficiency i e exo planetary transits As of mid 2010 the burst mode suffers from an extra overhead of 0 15sec plus one minimum DIT the exact value depends on the detector windowing but for the most likely window sizes it is a few tens of a second or larger an upper limit for a non windowed detectors is MINDIT 1 8 sec asso ciated with each DIT This makes observations with very high cadence requirements problematic Addressing this issue requires a modification of the detector readout mode Efforts to minimize the overheads are under way Please check the HAWK I web page for updates The fast photometry may be familiar to the users of fast jitter and burst modes of ISAAC NaCo VISIR and Sofl The main advantage of HAWK I in comparison with these instruments is the wide field of view that allows broader selection of bright reference sources for relative photometry F 2 Description The HAWK I detectors are read in 16 vertical stripes each The stripes span 128x2048 px and the detectors span 2048x2048 px each A window can be defined in each of the stripes but the locations of the windows are not independen
37. hotometry included Issue 86 0 30 Jun 2010 Several correction in the Appendix F Issue 87 0 02 Aug 2010 No changes from P86 to P87 Issue 88 0 05 Feb 2011 Many different small changes Issue 88 1 10 June 2011 Many different small changes once again Issue 89 0 01 Sept 2011 P89 Phase and Il HAWK I User Manual Issue 88 HAWK I as a CAD drawing attached to the VLT and in the integration hall in Garching HAWK I in a Nutshell Online information on HAWK I can be found on the instrument web pages and in Kissler Patig et al 2008 A amp A 491 941 HAWK I is a near infrared 0 85 2 5 um wide field imager The instrument is cryogenic 120 K detectors at 75 K and has a full reflective design The light passes four mirrors and two filter wheels before hitting a mosaic of four Hawaii 2RG 2048x2048 pixels detectors The final F ratio is F 4 36 1 on the sky correspond to 169 4um The field of view FoV on the sky is 7 5 x7 5 with a small cross shaped gap of 15 between the four detectors The pixel scale is 0 106 pix The two filter wheels of six positions each host ten filters Y J H Ks identical to the VISTA filters as well as 6 narrow band filters Bry CH4 H2 and three cosmological filters at 1 061 1 187 and 2 090 jum Typical limiting magnitudes S N 5 in 3600s on source are around J 23 9 H 22 5 and K 22 3 mag Vega HAWK I User Manual Issue 88 Contents 1 I
38. including all necessary overheads e Check whether you need any special calibration have a look at the calibration plan in Sect D this is what the observatory will give you as default You might need more and we will be happy to provide you with more calibrations if you tell us which Note however that night calibrations should be accounted for by the user Any additional calibration you might need should be mentioned in the phase 1 proposal and the corresponding night time to execute them must be included in the total time requested HAWK I User Manual Issue 88 8 3 PHASE 2 Preparing your HAWK I observations This sections provides a preliminary guide for the observation preparation for HAWK I in phase 2 both for Service mode SM or Visitor mode VM We assume that you are familiar with the existing generic guidelines which can be found at e http www eso org observing observing html Proposal preparation e http www eso org observing phase2 SMGuidelines html Service mode informations e http www eso org paranal sciops VA_GeneralInfo html VM informations We know that they are not super thrilling but a quick browse over them might save you some time during phase 2 3 1 HAWK I specifics to templates OBs and p2pp HAWK I follows very closely the philosophy set by the ISAAC short wavelength and NACO imaging templates 3 1 1 p2pp Using p2pp to prepare HAWK I observations does not require any special functions
39. ntroduction Ld Scopeof thisdocument sos ak 6G SHES SRE RBS SE RE CE DS Ox 12 Structure OF this doCument s oc 44 eo e N e oO a ee ee SE ale dt SORE eee rk ae Bc PEED Ew HORS ER eS e EO ee So We 1 4 Abbreviations and Acronyms 0000 2 eee eee eee Observing with HAWK I from phase 1 to data reduction PHASE 1 applying for observing time with HAWK I 2 1 Is HAWK I the right instrument for your Droiect a aooo 2 1 3 Limiting WARNES e q aos ee GRE Re ee ee ee 2 14 Instrument s performance 0000 ee eee 2 2 Photometry with HAWK 2 4 6 lt 8 a5 ee 4b 4 4 44064 bdo ws 2 2 1 Two ways to get reasonable photometry 2 2 2 Consider the 2MASS calibration fields 2 2 3 HAWK I extinction coefficients 23 The Exposure Time Calculator lt lt s o eg r 2eee ee bee Se bee Dae A oe Proposal Pont AA s aedi a BSE 4 BEDE CED Ee ESR Yee A 2 5 Overheads and Calibration Plan 2 2 PHASE 2 Preparing your HAWK I observations 3 1 HAWK I specifics to templates OBs andp2pp elk ON L ced ke bee a Seed oe eee woo es Gd hs Sk Gs Hae 3 1 2 Observing Blocks OBs Bille lt nue e Gee ee hb hE Ga ES GRRE EEE ES EEE SD Sees 3 2 Finding Charts and README Files Observing Strategies with HAWK I 4 1 Overview 4 2 Visitor Mode Operations 4 33
40. o the calibration plan In Visitor mode is also possible to observe bright objects using BADAO say switching active optics off Telescope and or instrument defocussing are however not permitted 4 3 The influence of the Moon Moonlight does not noticeably increase the background in the NIR so there is no need to request dark or gray time However it is recommended not to observe targets closer than 30 deg to the Moon to avoid problems linked to the telescope guiding active optics system The effect is difficult to predict and to quantify as it depends on too many parameters Just changing the guide star often solves the problem Visitors should check their target positions with respect to the Moon at the time of their sched uled observations e g with the tools available at http www eso org observing support html Backup targets are recommended whenever possible and you are encouraged to contact ESO in case of severe conflict i e when the distance to the Moon is smaller than 30 deg 4 4 Orientation offset conventions and definitions HAWK I follows the standard astronomical offset conventions and definitions North is up and East to the left All offsets are given as telescope offsets i e your target moves exactly the other way in arcseconds The reference system can be chosen to be the sky offsets 1 and 2 refer to offsets HAWK I User Manual Issue 88 12 in Alpha and Delta respectively independently of the instrument orient
41. on PA 0 deg is North along the Y axis East along the X axis for quadrant 1 For reference purposes we use the partly arbitrarily common meta system Quandrant offset in X pix offset in Y pix Ql 0 0 Q2 2048 153 0 3 Q3 2048 157 2048 144 Q4 0 5 2048 142 It is valid in its crude form to within a few pixels The distortion corrections for a proper astrometry will be added to all image headers Distortions including the obvious rotation component will be defined with respect to the above system First qualitative evaluations with respect to HST ACS astrometric calibration fields re covered the relative positions of objects to about 5 mas once the distortion model was applied a precision that should satisfy most purposes C 1 1 Center of Rotation and Centre of Pointing The center of rotation of the instrument is not exactly the centre of the detector array In the standard orientation North is Y East is X the center of the detector will be located 0 4 East and 0 4 South of the telescope pointing HAWK I User Manual Issue 88 26 The common reference point for all four quadrants taken as the centre of the telescope pointing and centre of rotation has the following pixel coordinates to 0 5 pix in the respective quadrant reference system Quadrant CRPIX1 CRPIX2 Ql 2163 2164 Q2 37 5 2161 5 Q3 42 28 Q4 2158 25 5 The CRVALI and CRVAI2 have the on sky coordinat
42. rates in two modes Burst and FastJitter In Burst mode the telescope is staring at the target for the duration of the integration INT NDIT xDIT and only one data cube is produced In FastJitter mode the telescope can jitter in the sky and many data cubes can be produced within one template In Burst mode it is possible to set the absolute time on which the observation has to be centered For example this is the case of Lunar occultations if one wants to observe an event at time T and sets a total integration of 60 seconds the template will start to collect data at time T 30 and end at T 30 The template ignores the timing parameters if they are set to zero Action sequence performed by the template is identical to that of the HAWKI_img_obs_AutoJitter template 1 Sets up the instrument including selection hardware detector windowing 2 Performs a random offset most users are likely to set the jitter box size to zero to keep the objects located on the same pixels which should reduce systematic effects from imperfect flat fielding 3 Acquires a images stored in a cube and continues as long as the number of the frames in the cube is equal to the value of the parameter DET NDIT this parameter defines the lenght of the cube HAWK I User Manual Issue 88 36 4 Goes back to step and repeats the actions until SEQ NEXPO cubes are collected Specific details The new windowing parameters DET WIN STARTX DET WIN STARTY DET WIN
43. t field If you are interested in doing stellar population studies be aware that the present read out mode does not allow to image field with bright stars in the Milky Way disk or bulge The basic characteristics FoV pixel scale can be found in the nutshell at the beginning of this document 2 1 1 Field of View The Fo of HAWK I is defined by four Hawaii 2RG chips of 2048 pixels each 1 pixel corresponds to 0 106 arcsec on the sky The detectors are separated by gaps of about 15 arcsec Thus the FoV looks like this HAWK I User Manual Issue 88 3 15 217 lt gt 7 5 Note that it is very tempting to point right onto your favorite target and to loose it in the gap since this is where the telescope points BEWARE of the gap between the detectors And see the details in Appendix C 2 1 2 Filters HAWK I is equipped with 10 filters 4 broad band filters and 6 narrow band filters see appendix A for detailed characteristics and the URL to download the filter curves in electronic form The broad band filters are the classical NIR filters Y J H Ks The particularity of HAWK I is that the broad band filter set has been ordered together with the ones of VISTA There are thus identical which allows easy cross calibrations and comparisons The narrow band filters include 3 cosmological filters for Lya at z of 7 7 1 06um and 8 7 1 19um and Ha at z 2 2 i e 2 09um as well as 3 stellar filters CH4 H2 Bry
44. t i e they all move together in a consistent manner that will be described further Therefore the total number of windows for each HAWK I frame is 4x16 64 because of the 4 detector arrays Along the X axis the windows can be contiguous or separated within each detector note that the four detectors only offer a sparse coverage of the focal plane i e there is space between the arrays so one can not have a single contiguous window across the entire focal plane The closest to that are four stripes across each detector The detector windows are described by the following parameters e DET WIN STARTX and DET WIN STARTY They define the starting point of the window within an individual stripe Note that the X axes on all detectors increase in the same direction but the Y axes on the upper and the lower detectors increase in opposite directions so when the values of DET WIN STARTX and DET WIN STARTY increase the starting points of the windows move to the right along the X axis and towards the central gap along the Y axis Note also that these parameters are different than the parameters DET WIN STARTX and DET WIN STARTY used to define the windowing in other modes Values larger than 100 px are recommended for DET WIN STARTY because the background at the edges of the detectors is higher due to an amplifier glow The allowed value ranges for DET WIN STARTX and DET WIN STARTY are 1 128 and 1 2048 respectively but if they are set to 128 and 2048
45. the FC should show the field in the NIR or at least in the red and the wavelength of the image must be specified in the FC and the README file e The IR magnitude of the brightest star in the field must be specified in the P2PP comment field of the OB HAWK I User Manual Issue 88 11 4 Observing Strategies with HAWK I 4 1 Overview As with all other ESO instruments users prepare their observations with the p2pp software Ac quisitions observations and calibrations are coded via templates and OBs OBs contain all the information necessary for the execution of an observing sequence At the telescope OBs are executed by the instrument operator HAWK I and the telescope are setup according to the contents of the OB The HAWK I Real Time Display RTD is used to view the raw frames During acquisition se quences the RTD can be used as well as for the interactive centering of the targets in the field Calibrations including DARKs skyflats photometric standard stars illumination maps etc are ac quired by the Observatory staff according to the calibration plan and monitored by the Quality Control group of ESO Garching 4 2 Visitor Mode Operations Information policy on the Visitor Mode operations at the VLT are described at http www eso org paranal sciops VA_GeneralInfo html Visitors should be aware that about 30 minutes night of night time may be taken off their time in order to perform the HAWK I calibrations according t
46. the window will only be 1x1 px so the users should select smaller values HAWK I User Manual Issue 88 30 e DET WIN NX and DET WIN NY They define the windowing by giving the sizes of the windows in each individual stripe For example if the user wants to define a window of 18x28 px on each stripe the corresponding values of DET WIN NX and DET WIN NY will be 18 and 28 respectively but these values will produce a fits file with four extensions each a data cube with 288 x28 NDIT because of the 16 stripes in each of the detectors along the X axis 18x 16 288 The allowed values are 1 128 and 1 2048 for DET WIN NX and DET WIN NY respectively but the users should take care that the starting point plus the size of the window along each axis do not exceed the size of the stripe along that axis The FastPhot templates are discussed in details further but for clarity we will point out here that they work in a distinctly different way with respect to the templates for other ESO instruments the windowing parameters are present only in the acquisition template and their values are carried over to the science template s by the Observing Software OS To modify the windowing one must re run the acquisition If an OB has been aborted the windowing parameters are remembered by the observing software as long as the DCS and OS panels have not been reset restarted so the OB can simply be restarted skipping the acquisition Figure 13 shows ex
47. tor gives a negative answer the template acquires an image saves it and then ends Otherwise an offset window is opened on the RTD to let the operator to define an offset and rotator angle offset and to modify the windowing parameters 5 The offsets including the rotator offsets are sent to the telescope and after they are exe cuted the template returns to item 3 The windowing parameters defined in the acquisition template are stored in OS registers and used by the science template later They can be accesed by the science template even if it has been aborted and restarted multiple times as slong as the OS has not been stopped and restarted Some additional details e The new windowing parameters DET WIN STARTX DET WIN STARTY DET WIN NX and DET WIN NY are this template They are used to draw on the RTD the locations of the 32 windows e The parameters BADAG and BADAO determine if the template checks and waits for guiding and active optics False check True no check These parameters are hidden i e they are not available to the user via the P2PP and if the user requires degraded AO performance for example because of extremely bright target they should request this in the README The BADAG is best left unchanged Please consult the HAWK saturation limiting magnitudes given earlier in this manual F 5 2 Science template HAWKI _img_obs_FastPhot This template is similar to the SAACLW_img_obs_FastPhot It ope
48. ution of the sky background for a given filter and DIT Please note that these values are indicative and can change due to sky variability especially for H band whose flux for a given DIT can fluctuate by a factor of 2 due to variations of the atmospheric OH lines This effect also impacts the Y J amp CH4 filters The Moon has an effect on the sky background especially for the NB1060 and NB1190 filters Similarly the variation of the outside temperature impacts the sky contribution for the K BrG H2 and NB2090 filters Due to the sky variations and in order to allow for proper sky subtraction we recommend to offset at least every 2 minutes Please be reminded that the minimum time at a position before an offset HAWK I User Manual Issue 88 Table 3 Sky background contribution amp Useful integration times Filter Contribution from sky RON limitation linearity limit Recommended DIT electrons sec DIT sec DIT sec sec Broad band filters Ks 1600 lt 1 30 10 H 2900 lt 1 20 10 J 350 1 15 140 10 Y 130 3 400 30 Narrow band filters CH4 1200 lt 1 40 10 NB2090 60 7 900 60 NB1190 3 6 110 14000 300 NB1060 3 4 120 14000 300 H2 140 17 400 30 BrG 180 15 300 30 14 is about 1 minute which corresponds to the typical time needed to perform a full cycle of M1 active optics correction The figure 3 shows the quality of the sky subtration as a function of pupil angle
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