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1. Alpy 600 User Guide Olivier Thizy olivier thizyOshelyak com Francois Cochard S francois cochard shelyak com INSTRUMENTS DCOO16B feb 2014 Alpy 600 spectroscope User Guide Olivier Thizy olivier thizy shelyak com Francois Cochard francois cochard shelyak com February 2014 Ref DC0016 revB Table of Contents Introduction 4 1 Discover your Alpy 600 6 Ll Ontol eD cx 99x 94994 EERE SEES ASIA EA 6 1 2 Technical specifications 6 L3 Alpy 000 elements us aces a OR ee EXE ARA 6 1 4 Mechanical interfaces an 8 1 5 VISUALODSCTVAON e wo bho woh ae aaa ee ehe ee 9 1 6 Alpy 600 principle 44 u 0 0 m 0 a u a EN ee RNA ee tr Rh RHO 10 1 7 Different slits sere reso 11 2 Alpy 600 Spectroscopy in slit mode 14 2 1 Configuration for imaging 14 2 2 Color or black amp white 18 2 3 Preview of your Spectrum 20 00 0 vu 0 u un un 9 o o users sum 18 2 4 Reference images o9 9 OV OO V nn os 19 241 Oscar a Un OR P mau ER SM WEE E xd x M eed 20 DAD IO IPIS 4x 90 93x 3c 909 III 20 2 4 3 Flat field spectrum 21 244 calibration Speci sis LS 25 0 0 a rare Esas 21 2 45 TUDICHDOBDSSEUJBOL 46 au 5 2 9 09 ee eee eR IAEA 21 20 Datigeliichon 45 3 55 oo 6 4 Sehnen TR D AAA 21 2
2. LSshelyak INSTRUMENTS 37 Here is a summary of a typical observing session to ensure data quality and productivity It is a basic checklist that you can use every time you observe Preparation Start up the equipment and cool down the acqui sition camera max 80 of cooling power Check your session parameters in AudeLA and ISIS observer s names observing site equipment working directory Prepare your session directory Check your computer time to better than 1 sec ond the exposure date amp time will be based on 1t Open a log file Run a test for all images sky Sun s spectrum calibration flat and check that all is Ok images correct file headers with proper data Prepare your target list Acquire dark and offset images and prepare mas ter images or copy from the master directory Get flat field images During observation For each target observation you will need to Locate the target start with a reference star Run the acquisition Get the calibration images Fill in the log file with any significant informa tion that will help in the future to remember the observing conditions Check that the images are properly recorded in the session directory Reduce the data as soon as possible At the end of the night Double check that you have all reference images dark frames offset flat fields neon reference sta
3. 60 277 000000 Camera Not connected uto PUE L mN 23 Y 2 15 04 2013 14 41 00 UT Mount Not connected Even though a CCD camera is generally better for astronomical applications cooling sensitivity no color LSshelyak 40 INSTRUMENTS bayer matrix effect using a DSLR camera makes astronomical spectroscopy accessible with a low bud get How to use a DSLR camera with the Alpy 600 is described in section 7 2 below 7 1 4 C mount camera adapter Most CCD cameras are today using T mount thread M42 x 0 75mm But there is also a large range of compact CCD cameras which use a C mount thread instead 1 diameter Some of them can be used with Alpy 600 thanks to the optional C mount camera adapter just keep in mind the CCD size which must be at least 8 5mm to get the full spectrum The C mount adapter replaces the main T mount adapter of the Alpy 600 7 1 5 Optical fiber adapter Alpy 600 can be used with a fiber optics The opti cal fiber adapter has a Type FC connector CHAPTER 7 APPENDIX SN 7 2 Alpy 600 with a DSLR camera Your Alpy 600 can be used with a DSLR camera A lot of people today have such a camera at home and it allows you to start in spectroscopy with a low investment Because of the long backfocus of DSLR cameras you must add the barlow adapter In the nominal configuration the spectrum length is about 18mm it is 6mm without the barlow Since pixels are
4. Settings rofle name reg 20 Cochard Dey ER Ful Save Header Database 2 Dispersion Ya E Na A i Continuum u Pal wi V Artimetic Na nud maize ee ru E mene EC gm i a yg a g amp 3 ll LSshelyak INSTRUMENTS 31 Alpy 600 user guide This response curve is very embossed This is different from what you saw on the Sun without the flat correction all the flat field details were smoothed Save the profile and re run the data reduction pro cess including the response file name in 2 General tab Now the result is only the star profile Tz m GOA You have now finished the data reduction for your reference star and you now have the dispersion law and the response curve these data will be reused for all the stars you observed during the night For the other stars you need run the data reduction process only once However you must pay special attention to an im portant point You re working in slitless mode and there is no way to put the next star exactly in the same position as your reference star spectrum There will necessarily be a shift between the reference star and the new target The dispersion law remains the same but it must be shifted to match the new star position To do it you need to identify one line in the new spectrum and give its wavelength to ISIS For instance here is a spectrum of 38 Lyn anot
5. or more 1 calibration spectrum image 5 reference star spectrum images or more and of course all the images of your object For each image you must check that there is no satu ration i A scientific measurement on an astronomi cal object spectrum requires not only a sin gle spectrum of this object but a whole set of images If you make sure you have all these im ages during an observing session data reduction will be easy and fast 2 5 Data reduction You ve now acquired all images for a full data re duction of the Sun observation In this section you will see how to proceed with ISIS software You will proceed with these images as if they were from any star 2 5 1 Prepare master files This step is to convert the series of reference im ages into single images called master files It is done very quickly in ISIS Go to the Masters tab and se lect each series of images offset dark flat to create a master Click on Go for each series LSshelyak INSTRUMENTS 21 Alpy 600 user guide P ss v5 2 0b 1 Image 2 General 3 Calibration 4 Go 5 Profile 6 Gnuplot Masters Tools Misc Instruments Settings Compute a cosmetic file Compute an uniform image synthetic flat field Name ESS Threshold 100 Constant Cosmetic file cosme Go Dark image dark30 Coordinate Ymax of validity zone 670 Compute a PRNU map Coordinate Ymin of validity zone 240
6. 5 1 Prepare master files o sy 21 2 5 2 First pass raw profile escri 22 2 5 3 Second pass wavelength eiler inle i adriana 22 2 5 4 Third pass Response curve COMECADO ee ae aaa es 24 3 Alpy 600 Stellar spectroscopy in slitless mode 26 3 1 Changing the slit position 4 vis sa ss 2 9 o9 XXX Feta vee tes aaa 26 3 2 Visual observation 26 3 3 Recording a star spectrum 27 3 3 1 Tuning the instrument 27 202 27 Stars OPCION de dde AAA 29 3 4 data reduction es errar AAA 30 SL First pass 6 ack se Gee ara 30 202 2 MCCOUd PASS uc au wow X 4b ue ED E EU ERROREM EUER S E X EDA eG 30 340 TAME DASS ka OOO HOE Re ee ew a OREO OEE Ree ee 31 4 Star spectra in slit mode 33 5 Next steps 35 5 1 Improve da tagu aliy 44 ages eee eh aes pS x 4 90k x Ee WIE 40 3 xk e 30m EES 35 5 1 1 Signal Noise Ratio SNR 35 SLA Ro ao dx war 6 75 9 9 09 ea ee RN 35 5 1 3 Wavelength calibration 36 5 1 4 Autoguiding guiding module ee 36 SLS XJOSImeHe fe SR 2 435564 44 5 66 55 6 6 eR ae eo wR GE 539444399 53b 36 INSTRUMENTS TABLE OF CONTENTS 5 1 6 Instrumental Response curve lll ses 36 5 1 7 WES AJOS ile se rara REGE arar 36 5 2 Improve PTOQUCUVIY wow oou deo oe deb om XO hok 4 OCA HERES
7. 5 2 06 1 Image 2 General 3 Calibration 4 Go 5 Profile 6 Gnuplot Masters Tools Misc Instruments Settings Root name Sun Object Sun Auto New Images to process Spectral calibration Generic name Sun Number E Predefined mode 1200 grooves mm 6 lines Predefined dispersion equation see Dispersion tool in Profile tab Calibration 0 Spectral calibration File mode 92400 type 200c Ist Output Instrument C8 Alpy 600 Atik 314L General parameters Observatory OHP Pixel size microns 645 Fixed Y value for sequence Observer F Cochard v Hour shift 0 R 494 Instr responsivity u J v Wavelength registration Wavelength shift A 0 Cosmic rays filter Heliocentric radial velocity comection v Optimal binning Auto atmosphere AOD 022 Rejection coef BIN Calibration prefix Atmo transmission Then switch to the 4 Go tab and click on Go Display the resulting profile Has v520 Rte E image eneral Calibrati 7E Profile 6 Gruplot Mast les sc Instruments et a Bl Eq a 7 der Database persion a l x Compare Contin Cars a Edt Pe Vu bos Arihmeti poe i 20 Wa Er Shit TE s La e S ooNemaize ur Crop Filter trotonight sun dat The profile is significantly different from the initial one made with no reference images at
8. 9 x Heade o 100 1000 vide oK e vance mme ES Automati ne Automatic 2 Mousses F AS To remove the emission lines double click on both sides of each line The line is replaced by a straight line LSshelyak 24 INSTRUMENTS Header Now move the cursor in the continuum panel to smooth the profile and remove all the noise in the profile Msc Instruments Settings Click on OK and save this response curve Now go back to the 2 General tab and fill in the response curve field Has 5208 Es Header This is the actual spectrum of the Sun You can compare it with the G2V theoretical spec trum click on the compare button CHAPTER 2 ALPY 600 SPECTROSCOPY IN SLIT MODE Ms v5204 e e NIE Misc ins struments Settings You can see that the result is excellent much of the detail that we could suspect to be noise is in fact the sunlight signal Summary The spectrum of the Sun is now fully processed To do it you ve run the data reduction process three times the first time to get the raw profile the sec ond one to include the wavelength calibration and the last one to correct for the instrumental response curve This process needs to be done only once per o
9. INSTRUMENTS to simulate a cold night Take a large number of im ages and create a set of master darks from them just once 5 2 3 Exposure time We suggest you always use the same exposure time for your observations typically 5 minutes 300 sec onds for faint objects Of course the total exposure time will depend on the object magnitude but you can adapt the total exposure time by changing the number of exposure They are several avantages to proceeding this way You can always use the same dark frames Data reduction is very fast no parameter is changed No risk of error during acquisition you never change the time There are some limits with this process for instance for bright or extremely faint objects but in general it will make your life easier 5 2 4 Prepare for your observation Amateur astronomers often wait for the last minute to decide what to observe We recommend to prepare for your observation well in advance If you properly organize your observing session you will optimize the target order their position in the sky higher is bet ter and so on You can even define the exposure time for each object depending on their brightness If you are looking for target and observing pro grams you can look at the Shelyak Instruments web site we ve listed many ideas ranging from from easy to ambitious 5 2 5 One directory per observing session This is a basic advice but doing spectr
10. dark we use most of the pixels are close to O ADU Click on the Go button and look at the console you ll see the number of hot pixels detected Around 100 500 hot pixels is considered normal e The master dark is not really a dark frame but the thermal map of the camera after the offset has been removed This is why the aver age level of the image is close to zero You can use the hot pixel map in the 2 General tab Simply enter the name of your map file in the field Cosmetic file and re run the data reduction ISIS will now include this hot pixel list in its calculation 5 1 6 Instrumental Response curve We have already described a simple way to get the Instrumental Response curve with ISIS In fact this is a tricky operation The response curve can evolve with some parameters like sky conditions target po sition in the sky air mass reddening and so on To be perfect you need a reference star close to your target of the same spectral type with similar mag nitude and this never happens Getting a bad re sponse curve will have an immediate effect the gen eral shape of your spectrum will be distorted It is a too long story for this document but keep in mind that getting the proper Instrumental Response curve requires some experience 5 1 7 Write a log file It can take various formats but we strongly encour age you to write a detailed log file when observing Note all the conditions of your observati
11. exactly what the eye needs a parallel beam is comparable to a beam coming from infinity Then if you put your eye behind the core el ement you ll see the spectrum LSshelyak 10 INSTRUMENTS Light source Alpy 600 core element GO za If you want to take an image with a camera you need to add the objective lens to focus the parallel beams onto the CCD sensor This is built into the Alpy 600 body Alpy 600 body Light source Alpy 600 core element Sly ak ins y 600 On the next picture you can see the objective lens part of the Alpy 600 body CHAPTER 1 DISCOVER YOUR ALPY 600 Cw The eye contains its own objective lens the crystalline lens Then it accomodates any beam coming from the infinite 1 7 Different slits The Alpy 600 is a versatile instrument As described in section1 6 a spectroscope requires a point light source to properly work the smaller the source the better is the resolution Alpy 600 contains several slits to fit to several usages Table 1 3 shows some of them To work with an extended source which is the case in most everyday situations use the standard slit 25um wide It is optimized for visual usage and for bench measurements The resulting spectrum is a wide band top line of table 1 3 In some conditions it is better to only have a small hole this way the spectrum is always at the same position in the image but it is more dif
12. first experience Here is how to proceed with your Sun spectrum Run ISIS ang go to the Settings tab Select ALPY 600 without calibration module in the spectrograph model and specify the working directory where you ve storedyour images FITS files 1 Image 2 General 3 Calibration 4 Go 5 Profile Spectrograph model ALPY 600 without calibration module Working directory c documents and settings user mes documents astro alpy Go in the tab Image Select your Sun image Sun 1 fit and display it If you don t see the spectrum it is probably because it is outside of the displayed zone You can move in the image using the scrollbars Select the checkbutton Reticule It will display the area of the image which will be selected for profile extraction If the area is not in the spectrum double click in the middle of the spectrum it will put the reticule there m 8 5 a el l Then click the button Next ISIS switches to the 2 General tab and updates automatically several fields Put Sun in the object name In the options area se lect the don t remove background checkbutton This is to tell ISIS that your spectrum is from an extended object the spectrum is not a single line in the im age Unselect wavelength calibration because at this stage we ve no data for calibration 1
13. http www astrosurf com buil isis isis htm 2 http www astrosurf com buil isis guide alpy tuto en htm LSshelyak 18 INSTRUMENTS 3 Calibration 4 Go 5 Profile 6 Gnuplot Masters Tools Misc Instruments Settings ul Images to process Spectral calibration Generic name Sun G Mme 3 Predefined made 1200 gooves mn ines Cubo A Predefined dispersion equation see Dispersion tool in Profile tab Spectral calibration ma Dak unm Rai E aas File mod 92400 Ist ona m lle mode o type exist Output Instrument C8 Alpy 600 Atik 314L General parameters Observatory OHP Pixel size microns 645 _ Fixed Y value for sequence Observer F Cochard Cosmetic file Y Sky not removed _ Hour shift 0 R 494 Instr responsivity si V Wavelength registration Wavelength shift A 7 Cosmic rays filter Ples name prefix and Object suffix E Heliocentric radial velocity correction V Optimal binning Calibration suffix neon 7 Auto atmosphere AOD 0 22 Rejection co e 45 Calibration prefix Atmo transmission Click on the Next button Isis switches to the 3 Calibration tab Check that Tilt angle Smile Y X coordinate of line at wavelength and A have the value zero Put 10 000 in the Radius value Uncheck the Auto after vertical coordinate Wists v5 24 fo S is 1 Im
14. in the image it is better to align the spectroscope axis to the telescope axis Ro tate Alpy 600 the whole instrument including CCD camera and external body in such a way that when you move the telescope in Declination the spectrum moves along the vertical axis Your instrument is now ready for observation 3 3 2 Stars observation Take some time to acquire several images of the star Of course if you make exposures of several sec onds which is more than probable you must rely on the telescope tracking If the tracking is bad the spectrum will move in the image during the acquisi tion and the result will be a band instead of a line As you did with the Sun you can immediately pro cess your first spectra with ISIS The only difference is that you now have a star spectrum Regulus in our case and you should ask ISIS to remove the sky background in the 2 General tab You should get LSshelyak INSTRUMENTS 29 Alpy 600 user guide a spectrum like this Misc Instruments Settings astrotonight regulus dat AG E D In astronomical imaging the signal level light level is very low and all the instrumental defects are pro portionally more important It is even more impor tant therefore to acquire the whole set of reference images to ensure good data reduction In slitless mode the flat field spectrum can be pro duced by putti
15. pixels and so on These effects are quite easy to correct using reference images offset dark flat fields The pre processing can be highly automated once you have made the proper reference images These images are offset dark frames flat field and cal ibration It is always better to take a series of images instead of a single image From the series you can make ei ther an average or a median This way you ll be able to eliminate any accidental events such as cosmic rays in images and improve the image quality ISIS software can manage series of images for all type of reference images Thermal Offset Dark Bias Dark Exposure t Exposure 2t Exposures t 0sec shutter ttt closed PShelyak INSTRUMENTS 19 Alpy 600 user guide 2 4 1 Offset image To avoid negative signal digital conversion CCD cameras have a fixed offset on the analog signal which is called Offset Any data readout from the CCD chip includes this offset ww Offset images are also called Bias in some documents In this User Guide we made the choice to use Offset but consider it is equivalent to Bias This offset is fairly stable and once you have a mas ter offset frame you can keep it for long time You can make one again once per year approximately It is also not too much temperature dependant Because it is very stable you can improve your data by taking a long series of offset frame aroun
16. range covered Click on the Display button for reloading the sun profile Then click on the Response button A re sponse panel appears select the G2V profile as refer ence Click on the Response button red Instrumental response Select a reference spectrum Reference spectrum c isis_data p_g2v dat Threshold up 5 Shift 0 A Threshold down o1 In the main window you now have 3 profiles your Sun spectrum the G2V theoretical profile and the division of both which is indeed the raw response curve I isis v5 200 tede Misc Instruments Settings Instrumental response g astrotonight _sun_20130320_723 f cochard fit sun Wavelength 5963 275 Intensity 1 0847 7 Automatic threshold Highlevel 02 Click on the OK button only the response curve re mains As you can see this profile is very noisy and there are some emission lines This is a side effect of the division between the profiles because the Alpy 600 and reference profiles do not have the same res olution To get the effective response curve you need to re move these lines and smooth the profile This can be done with the continuum button LESE eee 1 mage 2 General 3 Calbration 4 60 5 Profle 6 Gnuplot Mast en Tools Msc Instuments Settings Ecntnuumagusment rofi 20 ch Day amp x01
17. saturation r 7 Aud ACE visul le le Ez File View ges Ar innin togress lies El CE 4823 394 3718 000000 Camera A ARTEMIS CCD ATIK 314L uto ed mimi 57 Y 650 06 01 2012 15 06 16 UT Mount Not connected ug The Alpy calibration module contains a halo gen lamp which gives a perfect flat field spec trum 2 4 4 calibration spectrum As explained in section 2 5 3 you will process your Sun spectrum using the calibration information con tained within itself But you can also use a calibration lamp if you are working in slit mode For instance below is a neon spectrum sg The Alpy calibration module contains a cal ibration lamp made of neon argon and hy drogen which makes it very easy to calibrate in slit mode CHAPTER 2 ALPY 600 SPECTROSCOPY IN SLIT MODE r zu 7 Aud ACE visul e lt sx Files View Ima d T S 5 sec innin sitio rogress E AI i x 1 395 000000 Camera A ARTEMIS CCD ATIK 314L Auto 169 Y 888 05 01 2012 15 25 51 UT Mount Not connected 2 4 5 Typical observation To get all the data you need for a high quality ob servation here is a suggested list of all the images that you should have before switching off the equip ment This is applicable for your Sun observation but is also valid for night observations 7 offset images or more 7 dark images or more 7 flat field spectrum images
18. you made previously the exposure time must be much higher for stars If only tenths of a second were enough for Sun seconds or minutes can be required for stars If you ve chosen a bright star magnitude 0 to 3 then only few seconds is enough with a small telescope Anyway always control the exposure time to prevent saturation or low levels You should see something like this Move the telescope to position the spectrum in the center of the image Your telescope is probably unfocused Take spectra continuously while focusing the telescope Little by little youll see the spectrum get thiner and thiner When focused you should have this it must be only few pixels wide wy In slitless mode the width of the spectrum is directly linked to the star image size in the focus plane of the spectroscope slit plane Look at the left end of the spectrum there are clear absorption lines only for hot stars C If your image is black it can be due to the im age visualization thresholds In AudeLA click on the auto button bottom left to adapt the thresholds to the image You can rotate the Alpy 600 in the eypiece holder the spectrum remains horizontal in the image This is nor mal the orientation of the spectrum only depends on spectroscope position vs the CCD camera However it does not mean that you should put the Alpy 600 in any position If you want to make it easy to find and center the spectrum
19. 2D_sun fit War re tral profile is Display image er Plot After a few seconds the process is done Click on Display profile You should have this kind of image CHAPTER 2 ALPY 600 SPECTROSCOPY IN SLIT MODE r 1 W isis v5 24 sels 1 Image 2 General 3 Calibration 4 Go 5 Profile 6 Gnuplot Masters Tools Misc Instruments Settings Profile name sun Display oms DAT E EQ Ful y Save Header Database Dispersion Response Compare Continuu Edit FWHM Arithmetic H20 L Shift Normal g astrotonight sun dat Crop Wavelength 35 000000 Intensity 0 0189 V Automatic threshold Highlevel 4 Lowlevel 0 Fiter This is your first Sun spectrum profile There are a lot of absorption lines each of them is the signature of a chemical element in the external layers of the Sun s atmosphere photosphere However at this stage your profile is still not of a high scientific interest For three reasons at least The 2D image has not been pre processed The spectrum is not calibrated in wavelength The profile is not corrected for the Instrumental Response In the next sections you ll learn how to proceed to make these corrections and calibrations 2 4 Reference images Digital imaging is affected by several instrumental effects such as offset thermal signal read out noise hot
20. 968 277 1 723 3887 955 1 955 3834 227 0 773 RMS 1 974 1 When the polynomial is available re run the data reduction process including the wavelength calibra tion You will get the same profile but now calibrated in see the scale in the bottom axis note that the spectrum has been cropped between 3650 and 7300 A 3 4 3 Third pass The last operation is to establish the instrumental response curve In this document we used Regulus as reference star This is a B7V In the ISIS database Pickles there is no B7V but we can select a B8V the difference is not significant at our level Display this profile and save it in the current directory The spectrum has a much wider range than yours it goes from 1 000 to 10 000 A Reload your spectrum and click on Response W ss vs204 olez image 2 Generl 3 Calibration Instrumental response Select a reference spectrum Reference spectrum c users shelyak pictures isis database p_bBv dat Thresholdup 6 Shit 0 A Threshold down 0 so gg a gd a 3 ll Click on OK to get just the raw response curve Re move the lines and smooth the curve to reduce the noise Ti isis 5 200 E2537 jeneral Calibratio 5 Profle lastes Tools Msc Instruments
21. Generic name Dark image Gm Ofsetimae Image number 1 E Result eu Image number 11 m Result Go Also create a cosmetic file which records all the hot pixels in your camera Hot pixels are pixels that react differently from the others we consider they are de fective and the processing will replace their value by the average of the surroundig pixels The cosmetic file is made from the dark image set up the threshold in such a way that you get around 200 300 hot pixels this is a reasonable value W ss v5 2 0b 1 Image 2 General 3 Calibration 4 Go 5 Profile 6 Gnuplot Masters Tools Misc Instruments Settings Compute an offset image Compute an uniform image synthetic flatfield Name A Offset Generic name fi Image number 11 la Result CE Go Compute a dark image Generic name Dark30 000000000 Offset image offset Dark coef 1 Image number 11 E Y Vertical gain correction Result Coordinate Ymax of validity zone 670 Compute a PRNU map Coordinate Ymin of validity zone 240 Generic name EA Dark image AAN Ofsetimage 7 Image number 1 mu Result Image number 11 m Result Go 2 5 2 First pass raw profile The first pass is very similar to your first spectrum preview section 2 3 but you can now include the master files for pre processing In the 2 General tab select offset dark flat and cosmetic master files HA ss s
22. XE S 36 52l Keep tic Same setup uc a Eh a be AAA AAA 36 52 2 Dark rames Wbtary ss 4xxe x4eX 3 a 33344 rd 36 Doe EXPosireime 44 a 5 54 PP ENS S S E Sx 37 5 2 4 Prepare for your observation nennen een 37 5 2 5 One directory per observing session 37 5 2 6 Reduce your data quickly 37 5 3 Share your results 4 4 4 b 6 an AAA 37 5 4 Get pro Hke quality Specii auus ceo m om x dom dans ah ae ow Y Exo d 37 6 Typical observing session 38 7 Appendix 39 7 1 Alpy Modules amp Accessories 39 7 1 1 Alpy Guiding module 39 7 1 2 Alpy Calibration module 39 7 1 3 DSLR camera barlow adapter 40 7 1 4 C mount camera adapter 44444 4 4 0 CUR 41 7 1 5 Optical fiber adapter 44 4 wm 4 Ro e wk RO RO EEE RHR RE ati 41 7 2 Alpy 600 witha DSLR camera s ses m a a a AAA a prenne 41 C INSTRUMENTS 3 Welcome to the world of spectroscopy Alpy is a modular product line allowing you to start in spectroscopy in a very easy way and progress up to producing high quality spectra on astronomical objects Alpy 600 is the main module in this family It has several operating modes You can use it visu ally on diffe
23. ad Figure 1 1 Alpy 600 dimensions in mm C INSTRUMENTS 7 Alpy 600 user guide As far as possible standard threads have been used on the Alpy 600 parts to allow you maximum flexibility with your own equip ment For instance the external body is made with standard M42x0 75mm threads you can use a 2 eyepiece holder instead of the 1 25 one Several slits are available We ll see in the next chap ters how to change it and under which conditions to use each of them Loosen the three small screws around the spectro scope body and remove the Alpy 600 core element 1 4 Mechanical interfaces The Alpy 600 uses several standard threads for me chanical interfaces to adapt the instrument to your own setup The CCD camera interface is a standard T mount thread M42 x 0 75mm TELE TC You have now a view of all the elements of the Alpy 600 Core element Objective lens external body and nosepiece 1 25 The same thread is used on both ends of the exter nal body For instance you can replace the 1 25 nose piece by a 2 using a common 2 to T mount adapter ohelyak CHAPTER 1 DISCOVER YOUR ALPY 600 You ll see your first spectrum Look at different sources to see the different spectra types A tungsten lamp has a continuous spectrum The thread around the slit is of SM1 type external diameter 1 035 26 29mm 40 threads inch pitch 0 635mm A power savi
24. age 2 General 3 Calibration 4 Go 5 Profile 6 Gnuplot Masters Tools Misc Instruments Settings Image to process Sun i i Display 4 JI gt Next Fey Save Header Graticuk FWHM Statisti Tit Smile Line PSF X 168 Y 634 1485 Displayed image g astrotonight sun 1 fit 2013 03 20T17 20 24 677 Exposure 0 5s Domain Seuil haut ES EL Click on the Next button Isis switches to the 4 Go tab Click on the GO button ISIS runs the data reduction Bi ss v5 2 0b 1 Image 2 General 3 Calibration 4Go 5 Profile 6 Gnuplot Masters Tools Misc Instruments Go for process Object name Sun en Instrument C8 Alpy 600 Atik 314L a Observatory OHP Observer F Cochard Load the image g astrotonight Sun1 fit un orrection 500 Radius 100000 verse registi at intermediate Y coordinate 381 00 Bere Y1 403 50 Save image g astrotonight s fit sky not removed Save Ob product g astrotoi aes _Sun fit 2D image Adopted Y coordinate 381 Tilt correction second p E Write 2D image g astrotonight Ve fit Optimal binning Write raw profile g Seaton night raw 1 dat istration of individual spectra tensity of individual s ADU en n median for conie le 1 898063 490794 individual profiles We oo for proie 1 1 0000 alibrated profile 1D aped g astrotonight sun dat Pe en iced value before normalisation 1211423 99 Se 00 aped i9 astrotonight
25. all This differ ence is mainly due to the flat field correction 2 5 3 Second pass wavelength calibration You now have to establish the calibration law the relationship between pixel position and wavelength to display the spectrum in wavelength units The more lines you have the more precise is the calibration The dispersion law is usually a 3rd order polynomial To reduce the Sun spectrum you will proceed in a special mode in the Sun spectrum itself there is a list of known absorption lines that can be used for the cal ibration It is not the simplest way some lines can be quite difficult to identify but this is a reference spec trum that you can use without any additional mea surements Of course if you have access to a calibra tion lamp you can use it in preference wavelength Line 3933 Calcium K line 3968 Calcium H line 4307 G band molecular 4861 H8 balmer line 5167 Magnesium triplet 5270 Iron Fe line 5893 Sodium doublet 6563 Ha balmer line 3968 4307 3933 4861 5892 6563 5167 bes 5270 7 Click on the button Dispersion in the right side of the screen The dispersion panel appears Fill in all LSshelyak 22 INSTRUMENTS CHAPTER 2 ALPY 600 SPECTROSCOPY IN SLIT MODE the wavelengths above select absorption line and click on the first radio button matching 3933 A ke spec
26. ates the dispersion polyno mial law Compute spectral dispersion Emission lines Absorption lines pt compte ponon D gt some Line 1 3933 A4 0000000E 000 2nd Order Sien Som FREE A3 2234398E 008 aerea sind A2 5 825676E 005 4th Order Line 4 4861 830 236 Al 21945913 line 5 5167 975 757 AD 3064048 Line 6 5270 1019 705 Manual edition line 7 5893 1309 882 Line 8 6563 Save current line list Line 89 o line 10 Save current polynom Line 811 Line 812 A Load a line list Line 13 Load a polynom 4860 852 0 148 Reset 5172 872 5 872 5267 145 2 855 5891 122 1 878 6563 551 0 551 E RMS 3 776 d HS Close In the bottom area you have the RMS error re sulting from the calibration It should be around few A here the error is of 3 7 A Now re run the reduction process but selecting the Spectral calibration button in the 2 General tab You also have to select Predefined dispersion equa tion in the spectral calibration panel ER 1 Image 2 General 3 Calibration 4 Go 5 Profile 6 Gnuplot Masters Tools Misc Instruments Settings Root name Sun as Object sun Ato Net Images to process Spectral calibration Generic none SA Ga Meter 1 Predefined mode 1200 grooves ires Caibain 0 V Spectral calibration Dak dak File mode 92400 type xxx Ist Offset o
27. b serving session When you observe several objects in the same night you can reuse the calibration and the response curve to the first order you can consider that it only depends on the instrument and not on the observing conditions this may be a little bit more complex if you need a very accurate measurement We invite you to observe many spectra with this setup and run the data reduction process for each of them For a new object the only point to change is the input file and the source name in the tab 2 General and run the process in the 4 Go tab It takes only a few seconds LSshelyak INSTRUMENTS 25 Alpy 600 Stellar spectroscopy in slitless mode In the previous chapter you learned how to produce a basic spectrum You know what images are needed and how to process them to get the actual signal con tained in the light you observed You are now ready to go to the telescope and to apply the same method on astronomical objects So far you ve worked with the Alpy 600 in slit mode Ideally you should do the same with the stars But there is a problem when using a slit spectroscope the only field you get is the slit With an extended source daylight calibration lamp it s easy to aim for the source But stars are point like and it s not ob vious how to put it in the slit If the star is in the slit you get a spectrum but if it is just beside the slit you see nothing and when you see nothing
28. back on po tential improvements In addition spectroscopy is certainly still at a pio neering stage All the data you collect are of the high est interest for the scientific community don t keep them to yourself 5 4 Get pro like quality spectra Very often amateur astronomers think they are not able to provide high quality data comparable to those produced by professionals Of course amateurs usu ally don t have professional quality instruments but the quality of the data is more a question of method ology than instrumentation and you will quickly see that you can reach professional quality with just as much rigour You can even contribute to research in several Pro Amateur collaborations In a few words to get good quality data you need to pay attention to Accurate auto guiding Repeatable configuration and processing Correct data reduction SNR Wavelength calibra tion Instrumental response curve correction Standard file format see for instance BeSS file format Archiving and backing up the raw data ay Never forget that when you re observing the spectra of an object you re probably the only one doing it at this time on earth this is incred ibly valuable data and you must absolutely archive it very carefully raw images as well as processed data 2 www shelyak com menu spectroscopy educationnal amp projects 3 http basebe obspm fr basebe Accueil php flag lang en
29. comes focused you should see a large spectrum band which will become brighter and brighter The band is due to the fact that an unfocused star is like LSshelyak INSTRUMENTS 33 Alpy 600 user guide an extended object When you re close to the optimal focus the spectrum may disappear This is because the star image is now small and may be outside the slit In this case slowly move the telescope across the slit you should soon recover the star If not turn back the focus to extend again the object size until you re cover its spectrum Step by step you will be able to focus the telescope perfectly and put the star right in the middle of the slit At this point look through the flip mirror s eyepice and note the actual position of the star This position will have to be the same for the next observations If you put any star exactly at this position you ll have its spectrum in the Alpy 600 camera each time Tracking the star You ve been able to put the star in the Alpy 600 slit now you have to keep it there during the whole observation This depends of course on the quality of your mount and if it is precisely aligned or not You need to adapt the exposure time to ensure that spec trum remains very thin with no visual effects of track ing issues The spectrum must be thin and absorption lines must be sharp If after some exposures the spectrum disappears this is because the star moved out of the slit You ca
30. d 100 exposures and perform a median average to create a smooth master offset frame for your camera A median av erage is better than a simple average as it will totally remove out of the ordinary defects on some of your images such as cosmic rays for example To get an offset image put a cap on the Alpy 600 light entrance to ensure that no light comes in Take an exposure of 0 second binning 1x1 s E EE 34 307 281 000000 Camera A ARTEMIS CCD ATIK 314L to p CE 1 22 AY 06 01 2012 14 23 47 UT Mount Not connected Offset images are sometime called Bias im ages You can measure the average level in the image draw a rectangle and right click to get the statistics in the window r 3 76 Aud ACE visul tral File View Images Analysis Camera Telescope Setup Help Zn Help tor the Toot B Acquisition Setup 1 0 ic inni 1x1 7 Statistics in Window 997 Visul Max 353 Min 188 Mean 270 282562 Root mean square Deviation 16 515713 Sky Background Mean Value 273 375000 Sky Background Root mean square Deviation 14 979396 LA x E EI 34 xe34 257 000000 Camera A ARTEMIS CCD ATIK 314L to e 22 Y 98 06 01 2012 14 24 51 UT Mount Not connected 2 4 2 Dark frames CCD chips have a tendency to build up electrons over time particularly at high temperature This tem perature dependant eff
31. d in our factory during daylight start by looking at some lamps and daylight spec tra the Sun spectrum in fact record images and reduce data Secondly change to slitless configuration and in stall the Alpy 600 on your telescope start first with visual observation of some bright Stars then record amp process star spectra images Lastly take star and extended object spectra in slit mode This document follows this path Software The Alpy 600 is shipped with a CD ROM containing all the software tools you need to observe and process your data These software are free you can find their latest versions on the web Of course you can use your own software if you prefer In this document 1 http arasbeam free fr CC 4 INSTRUMENTS we use AudeLA for acquisition and ISIS for data reduction Equipment configuration The Alpy 600 can be used in many configurations but we cannot document all of them This documen tation is based on a specific configuration which fits Alpy requirements perfectly It will be easy for you to adapt the instructions to your own equipment amp software A Goto telescope able to point and track a star in autoguiding mode A C8 telescope with F 6 3 reducer A CCD camera Atik 314L It has a 8 9 x 6 7mm CCD chip with 6 45um pixels It covers the full Alpy 600 spectrum APC running under Windows 7 ug A CCD camera is the optimal choic
32. e calibration law can change across the FOV The key is to always put the spectrum at the same position in the image If you work in slit mode the horizontal position is constrained by the slit but also ensure that the spectrum is always at the same position vertically 5 1 4 Autoguiding guiding module Autoguiding is very dependent on your equipment Autoguiding means that you send the guiding image to the computer which controls the telescope based on star movement in the image AudeLA software can do that like many other software Autoguiding is not only for comfort when you acti vate the autoguiding you don t need to permanently check the guiding image any more but it also im proves the spectrum quality because it always repro duces the same conditions Consider autoguiding a high priority for obtaining good results 5 1 5 Cosmetic file The CCD chip has some hot pixels These pixels are much more sensitive than others These pixels will give wrong measurements It is better to remove them from your image This can be managed by ISIS software by creating a map of hot pixels All pixels considered as hot are replaced in the image by an av erage of the surrounding pixels To generate the hot pixel map you use a dark frame and record all pix els above a certain value In ISIS go to the Master images tab and focus on the Computing a cosmetic file area Enter the threshold value for instance 100 ADU in the
33. e extra care when changing its position and make sure that you can move it freely before turning it Cleaning the slit Over the time there can be some dust on the slit A dust particle in the slit is seen in the image as a dark line along the dispersion axis You can clean up the slit with a soft dry cloth or gently blow away loose particles Shelyak INSTRUMENTS 13 Alpy 600 Spectroscopy in slit mode In the previous chapter you ve looked at lamp spec tra using the Alpy 600 Now you probably want to take a picture of what you ve seen either to share it with others or to make measurements This is the purpose of this chapter Here you will work in slit mode with everyday light working on a bench 2 1 Configuration for imaging As explained in section 1 6 compared to visual ob servation we need to add more optics behind the grating to create an image at the focal plane the CCD surface These optics are contained in the Alpy 600 body The body is threaded for tuning the distance be tween the optics and CCD when it is mounted in the CCD camera adapter The nominal distance is about 19 5mm A threaded ring is used to lock the body in the focused position ly Watch out that the optics do not touch or damage your camera sensor Assemble the CCD camera adapter to your camera The camera used here has a T mount M42x0 75mm thread If you are using a C mount camera an optional C mo
34. e for as tronomical observations However Alpy 600 can also be used with a DSLR camera Because the backfocus distance between camera mount and sensor chip of a DSLR camera is much higher than in a CCD camera we ve designed an optical adapter for DSLR cameras Refer to Appendix for accessory descriptions Alpy modules Alpy is a scalable instrument This a family of mod ules to best fit your own needs amp observations These are the main modules The Alpy 600 is the main module It is the spec troscope itself It can be used in different config urations to cover most applications in astronomy amp the lab The Guiding module For astronomical applica tions it is difficult to ensure that all the light from the object you re observing goes into the spectro scope This module will help you to observe amp con trol the spectroscope entrance The Calibration module For accurate results a spectrum must be properly calibrated in wave length and intensity The calibration module sim plifies this operation by providing both a calibra tion and white light It can be used manually or remotely Accessories DSLR camera adapter C mount cam era adapter fiber optics connector Astronomical sectroscopy is a never ending story We have thought about a lot of applications you can find some ideas on the Shelyak Instruments website However we know that you ll invent new ones We ll be very happy t
35. e here we used the flat field It is closer to the actual star spectrum but is still strongly affected by the instrumental response curve 3 4 2 Second pass The wavelength calibration law can be established using the Balmer lines hydrogen lines which are the most visible in the spectrum They are spread out all along the visible spectrum like a geometrical se ries Here is the list of Balmer lines LSshelyak 30 INSTRUMENTS CHAPTER 3 ALPY 600 STELLAR SPECTROSCOPY IN SLITLESS MODE wavelength Line 3835 Hn eta 3889 HC dzeta 3970 He epsilon 4102 H delta 4340 H gamma 4861 H8 beta 6563 Ha alpha These lines are located as below A 6563 l With this information you can establish the cali bration law select a 4th degree polynomial because there are several available lines m u Compute spectral dispersion Emission lines Absorption lines pii Compute polynom st Order Line 2 4861 487 900 j A3 6626120E 006 rd Order Line 3 4340 335 324 A2 4 391670E 003 4th Order Line 4 4102 266 734 j Al 22620146 Line 5 3970 227 408 i AD 3292541 Calibration Line 6 3886 203 533 Manual edition Line 7 3835 187 347 Line 8 o Save current line list Line 9 it y Save current polynom Line 11 Line 12 Load a line list Line 13 Load a polynom 4339 909 0 091 Reset 4102 628 0 628 3
36. ect is called thermal noise The thermal noise is included in dark frames which are exposures taken with the camera shutter closed the offset is also included in dark frames Hot pixels are individual cells that are particularly sensitive to this thermal noise and tend to saturate quickly during long exposure These hot pixels have to be processed separately usually replaced by the average of the surrounding pixels An interesting prop erty of thermal noise is that it is linear with exposure time For example the thermal noise in a 2sec expo sure is twice the thermal noise in a 1 sec exposure This means that you can extrapolate any shorter ther mal noise frame from a master thermal noise frame with long exposure assuming you have mapped the hot pixels properly This is done by doing a median av erage of a long exposure dark frame series at least 7 frames if possible more Most astronomical software require both offset and dark frames to pre process your image The thermal noise is of course embeded in the dark frame Be very careful as the thermal noise thus the dark frame is very sensitive to temperature Make sure to use a dark frame taken at the same tem perature as your spectra If your camera doesn t have temperature regulation you should take dark frames close to the time you expose your spectra Some soft ware can still extrapolate a proper thermal noise map based on the area of your chip with no signal which is
37. ffset Ba Ba dao Ea Output Instrument C8 Alpy 600 Atik 314L General parameters Observatory Meylan Pixel size microns Fixed Y value for sequence TREES P Observer F Cochard Cosmetic file cosme sw Y Sky not removed Display the spectrum you can see that it is now cal ibrated in wavelength Database Nomalze y The calibration law can be established from any spectrum containing several known fea tures It is highly recommended to use a calibra tion light to do this when working in slit mode the more lines you can identify the more precise the calibration law will be LSshelyak INSTRUMENTS 23 Alpy 600 user guide 2 5 4 Third pass Response curve correction The whole instrument including telescope if any spectroscope and CCD camera has its own response to the light It is called Instrumental Resonse Curve For instance a CCD is much more sensitive to red than to blue light If you want to get the true spec tral profile of the source the Sun in your case you must correct for this very important effect The best way to do this is to record the spectrum of a known star a reference star and compare it to its theoret ical spectrum found in the literature In the current case you re observing the Sun and the Sun is a very well known G2V type star So we ll make the correction from a G2V spectru
38. ficult to see visually To a certain extent this is a way to reproduce in the lab what will be seen with stars second line There is another useful case working in slitess mode This is applicable to stars which are point like The advantage is that you ll see a bigger star field and you ll be able to find easily the star you re looking for To do that you can totally remove the slit from the Alpy 600 but it is better to keep in position the 3mm hole this way you ll limit the optical aberrations at the field edges and you ll not lose the slit third line Sometimes a wide slit is useful For instance when you have no guiding module but want to eliminate most of the sky background or when you want to collect the full star light if the star image is bigger than 25um In this case you can use the 300um slit last line The Alpy 600 also includes 50um and 100um slits Changing the slit position The slit position is easy to change It is mounted with two screws Remove the outer one and just loosen the central one Choose the slit you want and put its notch in front of the outer screw s hole Put back the PShelyak INSTRUMENTS 11 Alpy 600 user guide Standard slit 25um Hole 25um Wide slit 300um Table 1 3 Alpy 600 slits 12 INSTRUMENTS LSshelyak CHAPTER 1 DISCOVER YOUR ALPY 600 outer screw and tighten carefully the two screws The slit is a fragile component tak
39. finder The main tip is to slightly unfocus the star It be comes bigger in the focal plane slit plane and easier to find We recommend first working in slitless mode to be sure that telescope is close to focus If the focus plane is too far out the star can be huge even bigger than FOV and the light level very low wy Be careful if you unfocus the telescope only a samll fraction of the light will enter the spectroscope This is applicable only for bright stars Also with some experience and if your telescope is precise enough you can use your finder or even bet ter an electronic finder to put the star very close to the slit Then depending on the spectrum level you can de cide to refocus the telescope step by step By doing that the star may go out of the slit because it be comes smaller and smaller Then move the telescope again until you recover it You can make several iter ations until you juge that the star size and spectrum level are compatible with your observing conditions Again proceeding this way is more of a a fun chal lenge than a recommended observing method But it can show you the significant difference between slit less and slit spectra you ll quickly see that in most cases there is a much higher potential in slit spec troscopy Then keep in mind that by using the Alpy guiding unit you ll get the high quality of a slit spectroscope in a very easy way because you can permanently
40. h 4 mm 5 mm 6 4 mm 6 9 mm 9 mm 10 mm 11 mm 12 mm 12 5 mm 13 mm 13 8 mm 15 mm 16 mm A min 4560 4293 3920 3790 3650 3650 3650 3650 3650 3650 3650 3650 3650 A max 6055 6322 6695 6825 7380 7656 7923 8190 8319 8457 8500 8500 8500 Table 1 2 Covered bandwidth vs CCD size Note that above 7500 A the 24 order may recover the 1 order Look at the slit at the end of the spectroscope INSTRUMENTS 90 50 Description Dimension Alpy 600 Weight Resolution Power R 650nm Resolution Power R 450nm Spectral domain CCD min length Optical dispersing element Grating density Typical spectral dispersion Input beam F ratio Slit width standard Slit length Mechanical interface Value 200 600 400 370 750 8 5 Grism 600 480 F 4 25 3 M42 x 0 75 thread l mm A mm um mm CHAPTER 1 DISCOVER YOUR ALPY 600 Comment See drawing below with 1 25 nosepiece amp without CCD camera with 25um slit with 25um slit if smaller only a partial spectrum is visible grating prism Telescope beam can be from F 4 to F 10 optimal luminosity performance is at F 5 also included hole 3mm slit 300um 100um 50um hole 25um except for hole 25um Standard T mount or T2 Table 1 1 Alpy 600 specifications 58 15 CCD plane 19 90 M42 x0 5mm thre
41. h makes the beam parallel This parallel beam goes through a dispersing element usually a prism or a grating all outcoming rays of the same wavelength or color go in the same direction but the output angle differs for other wavelengths Then an objective lens collects all these beams and focuses them on the focal plane where we put the sensor Dispersion device grism Focus Collimator Objective plane Light source To make the source point like we usually use a nar row slit only the light which goes through the slit is spread out The narrower the slit the higher resolu tion the spectrum is but the less light goes through there is a compromise to find for each case In Astronomy we re lucky stars themselve are point like So when looking at stars we can afford to re move the slit Dispersion device grism CCD Collimator Objective plane Star light telescope Focus plane The Alpy 600 is designed in a modular way The core element consists of the the slit the collimator lens and a grism A grism is a combination of a grat ing and a prism The grating spreads out the light but also deviates the beam by a significant angle Using a prism brings the beam back onto the axis of the input light In this way we have an on axis instrument Collimator Grism grating prism source The light coming out the core element is then a set of parallel beams This is
42. he Signal It can be done by several ways Increase exposure time the SNR will be increased as the square root of the time multiplication fac tor Increase the telescope size this is why all as tronomers are always looking for bigger telescopes Ensure that most of the light is going through the spectroscope Star images and slits are very small a few um and it is very easy to lose a high pro portion of the light at the instrument The two main reasons for losing light at the spectro scope entrance are usually Telescope focusing If the focus is not optimal the object size will be bigger than the slit width Next steps and only some percentage of the object s light will enter in the instrument Position of the star in the slit When working in slit mode it is very easy to put the the star partly outside the slit The result is the same you lose a high percentage of your source The best way to improve this point is to check that when the star crosses the slit if any it almost disap pears from your guiding image Carefully tune your guiding camera exposure time to prevent any satura tion y If the star disappears from the guiding image when crossing the slit it means that most of light is going through the spectroscope With the experience you will know how much signal your instrument will get for a given magnitude You should also compare your data with others with sim ilar equipmen
43. her hot star In the 2D image you can easily identify the Balmer line at 4861 Measure its position and enter it in the ISIS field at the 3 Calibration tab 5 Profile 6 Gnuplot Masters Tools Misc Instruments Settings Y Graticule Seuil bas Run the process and get the fully processed spec trum 38 Lun Continue with the same process for all the stars you observed during the night Here is an other example mu Leo which is K2III bu Leo Betelgeuse Ae f jut al ehe W po wp You may observe that there are some shifts in the calibration law from one star to the other despite the realignement you made using a known line This is due to the fact that the dis persion law can be dependent on the spectrum position in the image To minimize this effect always put the spectrum exactly at the same po sition in the image You now know how to proceed with a complete and precise data reduction With experience you ll do this process in a few minutes for the reference star and in a few seconds for all the stars of the night LSshelyak 32 INSTRUMENTS In previous chapters you ve see how to use the Alpy 600 in slit mode see chapter 2 and slitless mode see chapter3 Slitless mode allows you to find your target more easily and capture all the light which is important for faint objects But slit mode has several advantages A better
44. is dramatically simplified by using the Alpy calibra tion module This module includes a halogen lamp for flat field images and an Argon Neon lamp for cal ibration It can even be used remotely to avoid any operations at the telescope during observations The Alpy calibration module is not required to produce LSshelyak INSTRUMENTS 39 Alpy 600 user guide A EEE NZ EC EEE ET p E 7 Aud ACE visul G AstroTonight Flat10 3 fit Fee File Setup Help quality data but it improves the repeatability and ef ficiency of your observations View Images Analysis Camera Telescope YAA 33074 X l Camera Not connected Auto id EA 49 Y 15 04 2013 14 39 10 UT Mount Not connected 7 1 3 DSLR camera barlow adapter The Alpy 600 has a short backfocus to comply with compact CCD cameras However in some conditions a longer backfocus is required This is the case for DSLR camera usage A DSLR camera with a T mount adapter has a long backfocus 54 85mm compared to most CCD cameras 15 25mm range The Alpy DSLR camera barlow adapter extends the Alpy 600 backfocus to match that required by DSLR cameras Calibration and flat field images made with the Alpy calibration module EU PEDE Ea 7 Aud ACE visul G AstroTonight ArgNe180 1 fit a File View Images Analysis Camera Telescope Setup Help Here the DSLR camera barlow adapter is mounted on the Alpy 600 3x C1355 X
45. is so big that the spectrum is unusable p Why not totally remove the slit You could do this but the size of the high quality field of the Alpy 600 is limited it is very good over the whole 3mm hole but decreases outside this area and keeping the slit in place is the best way to not damage or lose it 3 2 Visual observation To start with astronomical objects we invite you to look visually at a star spectrum Remove the Alpy 600 core element from the body loosen the three small screws around the body Shelyak 26 INSTRUMENTS CHAPTER 3 ALPY 600 STELLAR SPECTROSCOPY IN SLITLESS MODE This nosepiece can be put in a standard 1 25 eye piece holder RAR Attach the Alpy 600 core element to the nosepiece remove it from the external body Select a bright star in the sky preferably B or A type and point the telescope at it Now look through the Alpy 600 core element and focus the telescope to give a very thin spectrum Turn the Alpy 600 in such a way that the spectrum is horizontal with blue on the left and red on the right You should see something like this You can now look at different stars and bright ob jects 3 3 Recording a star spectrum After observing visually you will certainly want to record images You ve learned how to proceed with spectrum acquisition and reduction you ve put the spectroscope on your telescope now it s time to do both together 3 3 1 Tuni
46. limited to the vis ible domain Note that it is better to remove the IR cut filter from the DSLR camera to cover Ha this is a usual operation in astronomy The DSLR camera has a color sensor This makes raw images more complex to work with there is the Bayer matrix to manage Note that the over sampling in the DSLR camera configuration means that the Bayer matrix has no effect in practice on the Alpy 600 spectra resolution CHAPTER 7 APPENDIX INSTRUMENTS 43
47. lit towards a daylight source sky or window AAA 17 03 2013 09 45 38 UT Start your acquisition software Setup the CCD cam era cooling at 5 C for instance Take a first image of the spectrum You may have something like this The spectrum is probably unfocused and in any di rection To put it horizontally simply rotate the Alpy 600 core element in the body Even if the weather is cloudy the daylight is always the Sun light You don t need to wait for good weather when taking a solar spectrum INSTRUMENTS LSshelyak 15 Alpy 600 user guide To focus the spectrum turn the body in the CCD camera adapter Proceed step by step taking continu ous images wy When you turn the body in the CCD camera adapter you change the spectrum focus but also its orientation To see the focus improve ment it is better to keep the spectrum with the same orientation To do that fix the the CCD camera firmly we often use a small hand vice take the Alpy 600 core element in one hand to keep it in place and turn the body with the other hand When the spectrum image is correct tighten the threaded ring around the body and the three screws to lock the Alpy 600 core element You should have something like this The spectrum must be orientated with blue on the left and red on the right It is not obvious to see in a black amp white image With experience you will im mediately recognize the Sun
48. m When you observe astronomical targets it is neces sary to observe a reference star generally a hot star A type with few absorption lines close to your own target to prevent atmospheric effects A reference star is required for both calibration and response curve correction Of course the same star can be used for both needs ug Each observing session must start by observ ing a known hot reference star to allow the correction of any instrumental effect ISIS includes a database of spectra recorded at dif ferent resolutions Here is how to get a G2V star ref erence spectrum In the 4 Profile tab click on the database button The database panel appears Pickles NOAO Indo US Library CFLIB UVES bright stars 6520 A 6940 A domain Wavelength references ao y HD224926 BEIV y Aldebaran K lll Neon us Neon F Display Dispaly Display aon Balmer Elodie OHP 6200 A 6800 A domain MILES library IAC H20 Sun Vega A0V M HD000319 A1V HD000319 41V A i nn Type Mag D Display Display Display A B Ftypes only At the top left you can select an G2V star from the Pickles list Til ss 15204 kolla Normalize Lua amp ik 3 amp 3 E This profile is different from yours This is due to the Instrumental Response curve and the wavelength
49. n of course flip the mirror and look for it again but in practice it is probable that the star always moves in the same direction due to a mount alignement error So to return the star to its original position you can just move the telescope in the right direction You will quickly find this direction and the level of required corrections after some trials We may even suggest in some conditions to slightly misalign the mount This way the star will slowly move in the FOV but always in the same direction Then with experience you will know in which direc tion you need to move the telescope when spectrum level is decreasing e Of course if you have spent hours to align your mount this could be bad advice Only misalign your mount if you consider there is no such risk Pointing and tracking in wide slit mode with a flip mirror requires some experience but this is a real im provement compared to the slitless mode You will not be wasting your time if you do it Observing with the narrow 25um slit This section is for people who like challenges It is possible to observe in full slit mode using the 25um slit but it requires still more accuracy and patience compared with the wide slit The process is exactly the same as for the previous section but the tolerance for star positioning is more than ten times smaller 300um vs 25um However this is really feasible we did it even without a flip mirror only a
50. ng a diffuser in front of the telescope see an example below and illuminating it with a tungsten or halogen lamp during the night to pre vent any sunlight polluting the image The result will be like this in flats taken without a slit there is no evidence of the response curve All the details are smoothed out The wavelength calibration and response curve cor rection will both be extracted from a reference star spectrum Here is the list of the reference images you need to take in slitless mode to ensure a proper data reduc tion 7 offset image or more same as before 7 dark images or more same as before 5 flat field images or more take care of the right exposure time to get 80 of the maximum level 5 spectra of the reference star A or B type or more Point at several stars adapt the exposure time for each star and take 3 to 15 spectra of each of them 3 4 data reduction Create master files for offset dark flat fields and a cosmetic file from the master dark As you learnt in chapter 2 reduce your data in three steps to obtain the wavelength calibration and instrumental response curve 3 4 1 First pass First run the data reduction without wavelength calibration and response curve correction You should get this note that ISIS can export your profiles as PNG using the GnuPlot graphics tool This profile is different from the first Regulus one becaus
51. ng lamp has several bright emission lines and some bands The standard 1 25 nosepiece includes a standard filter thread M28 5 x 0 6mm you can easily mea sure the response curve of any filter mounted in a standard ring The Sun shows a continuous spectrum with a huge number of Fraunhofer absorption lines This shows that each source of light has it own spectrum and the spectrum reveals a lot of scentific information about its origin This will be the same for stars and any astronomical object each one has its own spectrum which reveals many physical parameters of the star 1 5 Visual observation Now take the core element and look at any light source classical lamp or spectral lamp or even the sky cloudy or not do not look directly at the sun it is far too bright Do not look directly at the Sun with or even without a telescope Shelyak INSTRUMENTS 9 Alpy 600 user guide i This document follows the standard con vention for presenting astronomical spectra The blue end of the spectrum corresponds to the highest frequencies or lower wavelength The red end is for lower frequencies or higher wavelength Usually in Astronomy we show the spectra from lower to higher wavelength From now on get into the habit of putting blue on the left and red on the right 1 6 Alpy 600 principle The principle of the Alpy 600 is as follows A point light source is sent to a collimator lens whic
52. ng the instrument In section 2 you ve seen how to tune your Alpy 600 to produce a focused and horizontal spectrum with the CCD camera You must start from there and switch to the slitless mode change the slit to the LSshelyak INSTRUMENTS 27 Alpy 600 user guide 3mm hole position Put the whole assembly into the eyepiece holder of the telescope Ensure that spectrum is horizontal with the right orientation blue on the left The external body includes a standard T mount thread M42x0 75mm If your Assemble the external body and the eyepiece ring telescope includes a 2 eyepiece holder you can on the Alpy 600 remove the Alpy 600 eyepiece ring and replace it by a T mount to 2 adapter optional Plug in the cables power supply and USB and bal Z 77 ance the instrument Do not forget to set your CCD temperature control We recommend setting up an empty direc tory on your PC to record all the images of the night LSshelyak 28 INSTRUMENTS CHAPTER 3 ALPY 600 STELLAR SPECTROSCOPY IN SLITLESS MODE Select a star to observe It must be bright and you should preferably look for a hot star A or B type be cause its spectrum has a clear continuum with some deep absorption lines In the images below we ob served Regulus which is a B7 type star When night falls point at the star using the tele scope finder Take an image of the spectrum Com pared to the Sun spectrum
53. o take your experiences into account to continuously improve this product do not hesitate to contact us if you have any comments We invite you to join the growing Shelyak Instru ments users and amateur spectroscopist community on the Spectro L Yahoo group and the Aras forum to share your own experiences and ask questions to the community We are really interested to see your results there It is now time to enter in this wonderful world Are you ready Enjoy Spectroscopy Fran ois Cochard 37 PA Qus tg the sem M ER pos Olivier Thizy 7 2 http www audela org 3 http www astrosurf com buil isis isis htm 4 http www shelyak com 5 http groups yahoo com group spectro l 6 http www spectro aras com forum 7 olivier thizy shelyak com 8 francois cochard shelyak com C INSTRUMENTS 5 1 1 Out of the box When you receive your Alpy 600 it is assembled in slit configuration ready for mounting on a tele scope and for imaging with a CCD camera The pack age contains the Alpy 600 as well as a tool set and a CD 1 2 Technical specifications The Alpy 600 specifications are given in table 1 1 and dimensions are given in figure 1 1 In addition the table 1 2 gives the wavelength covered depending on the CCD length 1 3 Alpy 600 elements Remove the external body from the big ring Discover your Alpy 600 CCD Sensor 17 2 KAF400 ICX694 KAF1600 CCD lengt
54. of common light sources The color version of each spectrum is colorized by software pOhelyak Alpy 600 user guide 2 2 Color or black amp white When you look visually at the spectrum you see a rainbow with beautiful colors Using most CCD cam eras you get only a black white image This is nor mal because the CCD camera is not color sensitive If you had used a color camera or a DSLR camera you would have a colored spectrum like this one You might think it is better to have the color it depends If this is only for sharing what a spectrum is this is true But if you want to make measurements on your spectrum a black 8 white camera is prefer able its surface is uniformly sensitive and there is no effect of the colored pixels Bayer matrix effect Anyway keep in mind that color or black white only depends on the camera the spectroscope itself works in color 2 3 Preview of your spectrum You ve recorded your first spectrum image That s great but not very useful in this format Usually a spectrum is presented as a profile giving the light intensity vs the wavelength To make the conversion from image to profile you must use spectral data re duction software Alpy 600 is provided with ISIS soft ware which is one recommended tool This docu ment isn t a tutorial of ISIS refer to the ISIS doc umentation and specially the Alpy tutorial but shows very quickly the basics for this
55. ons setup weather goal target list problems encountered dur ing the night It will help you in the future to make the best use of your data 5 2 Improve productivity 5 2 1 Keep the same setup The best way to improve your productivity is to al ways keep the same setup and always process the same way Of course observers often want to improve their setup this is a good behavior but as soon as you change parameters in your setup you have to adapt to change your process Sometime it is prefer able to keep the same conditions for both quality and productivity 5 2 2 Dark frames library Dark frames are long exposure time images at least as long as the exposure time of your objects And the more darks you take the better you will improve the SNR of the dark frame This is a very time consum ing operation something we should do at the end of the night when we know the longest exposure time But dark frames are an intrinsic charateristic of your equipment They only depend on the temperature and exposure time They don t depend on the observing conditions So there is no need to do them during the observing session itself you can do them once for in stance during a cloudy night or even during the day just take care of light leaks We suggest that you make your own dark frame li brary with different exposure times and camera tem peratures you could even put the camera in the fridge LSshelyak 36
56. oscopy will quickly produce a high volume of files To be sure that you will be able to proceed with a reliable data re duction it is important to not mix files from different observing sessions We recommend that you to create a new empty directory at the beginning of each ob serving session an observing session is generally an observing night Put your log file see section 5 1 7 in this directory 5 2 6 Reduce your data quickly It is very common that astronomers use the time during the night to observe and wait until the day af ter to reduce the data Be careful if you wait too long youll probably never reduce your data And having just raw data on your hard disk is the same as if you did nothing We strongly encourage you to reduce your data immediately after acquisition This way it CHAPTER 5 NEXT STEPS is all fresh in your mind and there is much less risk of mistakes during the data reduction 5 3 Share your results Our experience shows that the best way to improve your data is to compare your results with others When you compare your spectra with the results from ex perienced people with comparable instruments of course you can get an idea of the potential for im provement you have in front of you We encourage you for instance to observe Be stars and look at the BeSS database for comparable observations You can even send your spectra to the database they will be checked by administrators who give feed
57. r objects Archive your raw data securely Typical observing session LSshelyak 38 INSTRUMENTS 7 1 Alpy Modules amp Accessories 7 1 1 Alpy Guiding module As explained in this document working in slit mode gives some key improvements to your observations But in this mode you cannot see the telescope field and it is difficult to position the star on the slit The Alpy guiding module makes it possible to ob serve the slit entrance with a second camera usually called the guiding camera This allows you to posi tion the star precisely on the slit and to track it con tinuously This gives comfort of course but also im proves the quality of data and allows long exposure times If you re using your Alpy 600 for astronomi cal observations the Alpy guding module is almost mandatory In the image below you can see the telescope field and the Alpy 600 slit Appendix During the night you can observe and control the star position vs the slit File View Images Analysis Camera Telescope Setup Help Camera Not connected 4 CE 3274 x 240 710 000000 Auto ES HN 1 i45 Y 2302 15 04 2013 14 07 01 UT Mount Not connected 7 1 2 Alpy Calibration module As described in this document getting high qual ity spectra requires reference images These images can be made manually by putting a calibration or flat lamp in front of the telescope But this operation
58. rent light sources as well as on stars with a telescope You can also take pictures to share what you see and make scientific measurements you ll be surprised how far you can go in astrophysics with such a basic instrument For instance you ll be able to measure the temperature of a star define its spec tral class measure the expansion velocity of a nova observe the emission line of a Be star measure the expansion of the universe and so on The Alpy 600 design meets several objectives To offer an instrument which is easy to start with and fun to use but which is also powerful enough for people who want to go deeper into the science There is no compromise on the spectrum quality the optics are specially designed for this spectro scope To provide an affordable and scalable instrument Several additional modules are available You can use the Alpy 600 module alone to produce high quality spectra but adding the guiding and or cal ibration modules will make your astronomical ob servations much easier and more productive To be easily adaptable to your own setup tele scope camera the mechanical interfaces are standard and allow many different usages In spectroscopy there are different kinds of in strument slitless with slit or with fiber optics All of them have advantages and drawbacks It is the type of observation which defines the optimal configuration The Alpy 600 allows all of them Then
59. s is a trade off between the thin slit and the slitless mode Compared to slitless mode the size of the slit means Star spectra in slit mode that your spectrum is always at roughly the same po sition horizontally in the image and reduces the un certainty in wavelength calibration Also it reduces the sky background effect and gives more detail in the flat field The difference with the thin slit is that the spectrum resolution is still given by the star image size whereas the thin slit ensures that the resolution comes from the instrument itself Of course because of the field of view it is much easier to center the star To help you in star pointing we recommend using a flip mirror with a reticle eyepiece between the tele scope and the Alpy 600 This optional device will help you to put the star in a very precise position enough to put it in the wide slit at least Centering the star Use the telescope finder to locate the star start al ways with a bright one and flip the mirror to see the telescope field in the eyepiece Put the star well centered in the Field of View FOV Then flip back the mirror to let the starlight enter the spectroscope Take continuous images until you can see a spectrum in the image If there is nothing put all the thresh olds at max sensitivity and change the focus of the telescope the first time you install the flip mirror the telescope is probably very unfocused When star be
60. see the star you are observing in your guiding image LSshelyak 34 INSTRUMENTS You have now passed all the steps to produce your first reduced spectra With experience you will per form the acquisition and data reduction more and more efficiently In this section we ve put some tips and tricks to improve your observations Improved observations means better data quality up to pro fessional quality level data and better efficiency or productivity in your observing procedures Most of the advice below assumes that you re working in slit mode ie you have a guiding module 5 1 Improve data quality 5 1 1 Signal Noise Ratio SNR Star light is faint and you spread it out with your spectroscope At the end of the chain only a few pho tons reach each pixel of your CCD camera The whole instrument telescope spectroscope camera limits your ability to detect faint signals The quality of your spectrum is directly linked to the level of signal you get on your CCD compared to the noise of the in strument which is its limit of detection This is what we call the Signal Noise Ratio SNR Improving SNR can be done in two ways reduce the noise or increase the signal Reducing the noise is hard it is limited by physics But we can do it to a certain extend For instance by cooling down the camera you reduce the internal activity of the CCD and reduce the noise The best way to improve SNR is then to increase t
61. spectrum Refer to this image to put it in the right position You ve completed the most complex part of spec troscopy with Alpy At this stage your camera is equiped with the spec troscope and any image you take will be a focused and horizontal spectrum of the light coming into the slit wy When The Alpy 600 is focused you can remove the core element and put it back quickly the focus is not lost You ll have only to tune the rotation angle to put the spectrum horizontal in the image Test now different kinds of lamps tungsten power saving lamps neon lamp Alpy calibration lamp each source has its own spectrum The table 2 1 shows some examples For the next step record at least one image of the Sun spectrum in FITS format wy FITS format is the image file format for As tronomy This is a format which keeps the whole information in the image no compres sion and adds some key data in a file header such as date image size observer observing site object coordinates and so on LSshelyak 16 INSTRUMENTS CHAPTER 2 ALPY 600 SPECTROSCOPY IN SLIT MODE Description Sun light Halogen lamp flat field lamp of the Alpy calibration module Candle light an Neon Ay cc modi 3 Neon lamp White LED Power saving lamp Blue paper illuminated by a halogen lamp Red paper illuminated by a halogen lamp Table 2 1 Some examples
62. t as an external reference see section 5 3 If you see that this level is lower than is usual take some time to find the source of this loss To go further into SNR improvement you can mea sure the total power of your spectrum and tune the telescope focusing to optimize this measurement 5 1 2 Resolution If you work in slit mode the resolution of your spectrum comes mainly from the spectroscope itself The resolving power of the Alpy 600 is approximately R 600 around Ho The ISIS software calculates the actual resolving power as part of the data reduction Check that your actual result is close to this value _ The resolution is calculated from the width of the calibration lines AA FWHM of cali bration lines The better the focus of the calibra tion lines the better is the resolution 1 Resolution power gives the ability of the spectroscope to see details It is calculated as A AA whereA is the smallest visible detail in the spectrum LSshelyak INSTRUMENTS 35 Alpy 600 user guide 5 1 3 Wavelength calibration Take special care when performing the wavelength calibration Normally you should have an RMS smaller than 0 5 Take the time to record a calibration quite often and use this image for the data reduction Al ways double check that there is no major error in the calibration The simplest way is to look at the positons of the balmer lines visible in most types of stars Also remember that th
63. there is no way to define in which direction you must move the telescope gt From a practical standpoint this is not feasible at least when starting in spectroscopy You ll see in chapter 4 how to deal with that For now switch to slitless mode applicable for point like sources Slitless mode has advantages For instance it col lects the full light of the star whereas slit mode has some loss at slit entry This is useful for very faint ob jects but it has also some drawbacks there is no way to use a calibration lamp which is an extended source and the position of the spectrum will move in the field depending on your telescope tracking In a few words using the Alpy 600 in slitless mode is the way to work when you have no guiding device but this is not the simplest way to get accurate mea surements The good news is that when you become familiar with this process switching to a guided mode will reveal how easy it is to do spectroscopy ug The observation itself must be done during the night but the preparation of the tele scope and the tuning of the Alpy 600 with the CCD camera has to be done during daylight p 3 1 Changing the slit position You ve seen in section 1 7 how to change the slit Here you should select the 3mm hole the big one Now if you take an image of Sun light you ll see a very rough spectrum as if if it were strongly defo cused It is in fact focused but the light source
64. tral dispersion Emission lines Compute polynom er mnes A4 0 000000E 000 2nd Order Line 2 A3 1 856999E 007 3rd Order Line 83 A2 2 966710E 004 4th Order Line 4 Al 32327032 Line 5 AD 3017827 Calibration Line 6 z Manual edition Line 7 Line 8 Save current line list Line 9 MEA Save current polynom Line 11 Line 12 Load a line list Line 13 Load a pobmom Rest Now double click in the profile on each side of the absorption line at 6563A This will measure precisely the center of the line in pixels The next line will be automatically selected TE isis vs2od Te Ta Image General 3 Calibration 5 Profile FEN Compute spectral dispersion 5 je Emission in es Absorption lines es a ful Line 1 3933 260 434 M 0 000000E 000 2nd Ord Line 2 3968 OF a 186 3d Ord line 3 4307 A2 2966710E004 Ah Ord Line 4 4861 Az 3 ine 5 Calibration E Cose Line 6 Manual edition Une 7 589 Line 8 63 Save curent line Line 9 Sa ment Line 10 auSemamstsoinn od Line 11 ne U toadainets ne ceada pobman lt lt Reset oe rotonight sun dat Wavelength 6 000001 sity TT Ato she Lor Repeat the same operation for each recorded line When it is done select 3rd order option and click on button Compute polynomial Based on the lines you ve selected it calcul
65. unt adapter is available see appendix 7 1 4 Shelyak 14 INSTRUMENTS Put the Alpy 600 core element in the body It can turn freely this will be used to put the spectrum horizon CHAPTER 2 ALPY 600 SPECTROSCOPY IN SLIT MODE The first point to check is that the image is not satu rated The CCD camera has a capability of recording tally a certain level of light this is the dynamic range spec ification If the source exceeds this level the camera considers it is like a maximum light and cannot see any details in it The Atik 314L camera has a dy namic range of 65535 ADU If a pixel in the image is above this value it means that image is saturated To solve this problem you must reduce the exposure time or reduce the source intensity if it is possible At the opposite end if the maximum level of the image is at the bottom end of the dynamic range of the camera you lose the capability to see details in your images You can then increase the exposure time The optimal level is about 80 of the camera max level There are three small screws around the body to eu ent pose If the image is totally black or white it can be due to the image visualization threshold settings in the software Move the cursor in the image and check the pixel level bottom right Or change the thresholds by clicking on Auto button bottom left Now put the camera in a stable position and point _ ET SEE the s
66. usually small in a DSLR camera 5 6um range the spectrum is over sampled Installing the DSLR camera barlow adapter The DSLR camera barlow adapter is mounted on the back of the Alpy 600 If necessary remove the main ring for better access to the thread Make sure to tighten it firmly She yak INSTRUMENTS 41 Alpy 600 user guide a CCD camera refer to section 2 1 You can use sun light to make this operation The Alpy 600 is mounted on the DSLR camera with a standard T mount adapter But you may also use any lamp with emission lines such as Neon or Argon DSLR camera vs CCD camera You can use your Alpy 600 and DSLR camera with all Alpy modules and accessories guiding calibra tion fiber optics for lab activities as well as for As tronomy However keep in mind that a DSLR camera doesn t have the same performance as a CCD camera The main differences are Sensitivity A CCD camera is roughly ten times Focusing the Alpy 600 more sensitive than a DSLR camera It means that We suggest installing your DSLR camera on a tri for the same result you will need ten times longer pod Focus the Alpy 600 with the same method as for PShelyak 4 INSTRUMENTS exposures This is not a problem for bright objects but it limits the observation of faint targets Spectral bandwith is smaller for a DSLR camera A CCD camera can go up to near UV and near IR where DSLR camera is strictly
67. very easy in the case of Alpy 600 spectra You do not have to rebuild your dark frame every night you can create your library of dark frames taken at different temperatures and use it for several months A dark frame is taken with the same conditions as the target spectrum exposure time temperature but with no light coming into the spectroscope For instance if your star spectra are made with 300s exposure dark frames must be taken with the same duration Here is a typical dark frame of 300s binnng 1x1 of course 4 xi JEE 481 306 403 000000 amera A ATIK to ge C E Ow Y 06 01 2012 14 42 32 UT Mount Not connected E Shelyak 20 INSTRUMENTS 2 4 3 Flat field spectrum A flat field spectrum is obtained by illuminating the spectroscope with a continuous spectrum of white light Ideally it should be a lamp that has the same energy level in each wavelength It doesn t exist in real life As a compromise we use tungsten or halo gen lamps but not power saving calibration lamps or sunlight The exposure time must be choosen to give 80 ot the max level of the camera This image is mainly used to determine low fre quency non uniformities caused by dust on the CCD front glass for example or overall instrumentation vi gneting Make sure to take a series at least 5 expo sures of flats The signal has to be as high as possible without any
68. wavelength calibration using calibration lamps Observation of extended objects nebulae comets galaxies Allows the sky background to be removed useful for faint objects or urban observing conditions The resolution depends only on the slit not on observing conditions tracking seeing telescope focus For these reasons most observations are made in slit mode In this chapter you ll see how to work around the problem of pointing and tracking a star in slit mode though the best solution is definitely to add the Alpy guid ing module to your Alpy 600 This is a device which shows you the entrance of the slit you can see the star you are observing You can use this image to move the star onto the slit and track it If you plan to make regular observations of astronomical objects this is a required device for comfort and efficiency but also for the quality of your measurements It is described in 7 1 1 However there are some ways to observe in slit mode even without the guiding module It requires some experience most astronomers like challenges There are two approaches 1 Observing with the wide slit and a flip mirror 2 Observing with the narrow 25y slit The first one is really accessible The second one is clearly a challenge but we did it ourseleves Observing with the wide slit The Alpy 600 includes several slits refer to section 1 7 One of them is the wide slit 300um wide Thi
69. you can decide for yourself what is best in your case Prerequisites Spectroscopy is a very large subject Some parts are very easy For instance looking visually at a spectrum during daylight or with a star requires no experience However if you want to take images or make scien tific measurements it is highly recommended to have some experience with your instrument telescope and camera In this document we assume that you re new Introduction to spectroscopy but that you re already familiar with the basics of astrophotography Specifically we ll not cover here the following points Setting up and tuning your telescope You must be able to point and track a star Ideally you should have autoguiding with external parallel optics off axis or with the Alpy guiding module nstalling starting and using most common soft ware You should have a PC available running un der Windows we use MS Windows 7 in this doc ument Astronomical imaging You should know what is a dark an offset a flat field and classical image processing p If you ve already made some deep sky im ages with long exposure and good process ing moving to spectroscopy will be easy for you a new adventure which gives access to a new dimension Recommended learning path Here is a proposed learning path to guide you step by step through the discovery of your Alpy 600 First use the Alpy 600 in slit mode as it is con figure

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