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C100/RetroCam Observing Procedures

You may also refer to the Carnegie Supernova Project RetroCam manual:



1. Initialize System

  • Field of view is now: ˜ 3.4' arcmin

1.1 Instrument Control:

  • The technical staff will start the system for you; but in case a restart is needed (for example if the observer's computer -Caballo or Clarity- needs a reboot), do as follows:
  • Log into Caballo (or Clarity) as obs1, obs2, or obs3 (get username and password from the technical staff)
  • Double click on the RetroCam icon on Caballo or Clarity dock.
  • The setup  RetroCam window will pop up.
  • Type in the observer name under 'Observer'
  • Make sure that 'Camera' and 'Telescope' are Online and their right check marks are checked. 
  • Then click OK
  • The RetroCam window will pop up.
  • Go to the task bar on the top of Caballo window, click on Camera and then select DataPath. A window will pop up where you can define the directory where data will be stored. If that direcotry does not exist, the system will offer you the possibility of creating it.
  • From the Camera menu you should also launch the QuickLook Tool window where images will be automatically displayed. For a detailed description of the QuickLook tool functionalities refer to this web page.
  • Go to the Telescope menu  (also on the top task bar) and open the TeleGUI and  Airmass.
  • 1.2 Data Inspection and quick reductions:

  • Open IRAF by clicking on the IRAF icon in the task bar (this will bring up an IRAF terminal and DS9).
  • In the IRAF terminal, load the RetroCam observing package:
    cl> retrocam
  • In the IRAF terminal, go to the data directory, e.g.:
    cl> cd /Volumes/Data_Caballo/RetroCam/20140511_02
  • See the use of observing scripts in Section 4 below.


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2. Calibrations and Telescope Setup

    2.1 Dome Flats

    • Ask the operator to set the telescope for dome flats
    • In Retrocam-Control window set:
      • Exptime = 5
      • Readmode = Double
      • ObjType = dflat
      • Loops = 15
      • Object = Domeflat 
    • Turn ON quartz light (max voltage is 480), suggested voltages are as follows:
      • Y:  335
      • J:  295
      • H: 265
      This way you should get about 12,000 ADU on average.
    • In Retrocam-Control window select a filter and click the Go button to start a loop of flats.
    • When done, turn OFF quartz light.
    • Click Go again to get "lamp-off" flats.
    • Change filter and lamp level, and repeat the two previous steps.
    • When the sequence of dome flats is complete, check that the quartz lamp is OFF.

    2.2 Sky Flats

    • Dome flats may be all you need for flatfielding your data, but if interested in getting twilight flats, ask the operator to go to an empty field or just try pointing to Zenith if it is still  clear. Beware that some of the empty fields are dark clouds in the Milky Way which contain plenty of stars in the NIR. 
    • In Telescope Control window set dy = 10 (10 arcsec steps).
    • In RetroCam-Control window set:
      • Exptime = 5
      • Readmode = Double
      • ObjType = tflat
      • Filter = Hc
      • Loops = 1 or 2
      • Object = Skyflat 
    • Start a test exposure with Go. Repeat until you have gone down below 20,000 ADU. Make sure that average counts are indeed going dwon between subsequent integrations. If not, the chip is still saturating.
    • Change Exptime = 5.
    • If you want to reset the counter in Filename to the first unused number you had before the tests you need to go to  the   Camera menu on the task bar on top of Caballo/Clarity display.
    • Push Go to start the first flat.
    • Push the N or S buttons in Telescope Control window between exposures.
    • Alternatively, you can do the offsets by running a dither macro: In RetroCam-Control window press Dither and select
      • Dither-Pattern = rot-5
      • Dither-Step = 15
      • Guider = none
      You can change the exposure time while the telescope offsets between integrations.
    • Take at least five (5) images.
    • Change Filter to Jo and repeat the procedure above.
    • Take at least 5 images with 8,000 to 20,000 ADU, and offsetting the telescope between them.
    • Finally, go to Filter = Yc 
    • If you don't get enough counts you can ask the TO to move the telescope  West 1h or 1.5h to increase the illumination.

    2.3 Telescope Zero-Point (CSET)

    • Ask the operator to point to a bright star for the zero-point
    • In RetroCam-Control window set:
      • Exptime = 3
      • Readmode = Double
      • ObjType = test
      • Filter = Yc
      • Loops = 1
      • Object = Test
    • Take an image with Go.
    • In the Display window click on the center of the bright star.
    • In the same window click on Center Telescope.
    • In Telescope Control window click on the 0,0 button.
      The telescope will now center the bright star.
    • Ask the operator to do the 'CSET'.

    2.4 Telescope Focus

    •  The first estimate for the focus values with a T=8-9 gives a first offset of +0.15 units higher than Y-H. E.G.: first focus for Y-H=43.00; J=43.15 on July 18th 2011. A focus sequence is needed at the beginning of each night and sometimes during the night also. The image quality needs to be monitored along each observing sequence.
    • If the focus is fairly good, ask te operator to start a sequence, take a single 10sec image, and wait for the operator to change the focus value
      • Exptime = 10
      • Filter = Yc
      • Loops = 1
      • ObjType = test
      • Object = Test,
    • Use 'disi' iraf task to 'display and imexam' the images; use the 'r' and 'e' keys to judge their quality and find the best focus. For example,   'disi 15 1' will display irr_00015_001.fits (image 15, loop 1) and run imexam on it.
    • Tell the operator what the best focus was so that he does an fset.

    2.5 Darks

      Darks may be taken in the afternoon before the observations,  in the morning, or during the night in case no object can be observed.
      Darks should be taken with each exposure time used during a particular night.
      Therefore, you may need to add darks in the morning, once you know which exposure times you have used.
      Note that this includes all the exposure times used for twilight flats.

    • In the RetroCam-Control window select:
      • Readmode = Double
      • ObjType = dark
      • Filter = dk
      • Loops = 15
      • Object = Dark
    • Set one of the required exposure times in ExpTime.
    • Click Go to start taking the darks.
    • Repeat with every required ExpTime.
    • Darks can be obtained using a macro. In that case, after setting Filter, ObjType, Loops and Object as explained above, the macro name is  entered under 'File'  and the sequence is started with 'Execute'. There are 2 different macros available: darks_5_10_30 and darks_5_10_20_30_45. If different exposure times are needed, a new macro can be defined at /Users/Shared/Library/Application\  Support/RetroCam/Macros/ directory.


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3. Observing

    3.1 Science targets

    • In the RetroCam task bar click on File and Open ObjectList. This will bring up a window where you can select the ObjectList you want to open. New lists may also be created.
    • You can use the buttons to Add, Edit, or Remove an object and also editing a new object list.
    • Remember to save your changes or else you'll lose them when you close the application.
    • The Preview button shows the situation of the selected target in the Airmass and the Skymap windows without having to point the telescope to the object.
    • The SendTo button is now working for sending the target coordinates to the TCS.
    • Select an object and send it for the operator to move the telescope to the target.
    • To check that pointing and focus are good, in the RetroCam-Control window set:
      • Filter = Yc or Jo
      • Exptime = 10
      • Loop = 1
      • ObjType = astro
      • Object =   name will be automatically loaded from the Object List
    • Take a test image by clicking on Go.
    • If you need to correct the pointing, use the dx and dy offsets and the directions panel in the Telescope Control window.
    • The upper-left (NE) quadrant should be avoided because it contains several dead spots.
    • If wanted, reset the Filename counter to the value previous to the test (unless you want to keep those), and set Exptime, Loops, and Macro.
    • To define the Macro, press Dither and select the options of Dither-Step, Dither-Pattern, and Guider. Make sure you select Guider = auto.
    • Ask the TO to start guiding (in general, guiding is not needed for individual exposures of 45s or less). If you decide not to guide, select Guider =none in the Dither macro and loops = 1.  You can do several sequences to get the desired total exposure time.
    • Start a dither sequence by pressing Execute in the RetroCam-Control window.
    • Also remember to apply the focus offset when you change from/to J.
    • You can make use of the quick-processing scripts described in Section 4 below to check the quality of the data and perform quick photometry, and adjust exposure times or dither sequences.

    3.2 Standard Stars

    • If the night is photometric, you may want to observe at least 3 or 4 Persson Standard stars.
    • In the Object List window go to File and Load.
    • Select the file persson.objects and click Open.
    • The list of Persson standards is displayed.
    • Select a standard from the object list and SendTo the TCS, and tell the operator to slew.
    • In the RetroCam-Control window select:
      • Exptime between 5 
      • Readmode = Double
      • ObjType = standard
      • Loops = 1
      • Object = SJ####   
    • Take a test exposure with Go and check the field and exposure time.
    • You may need to move the star off the quadrant divisions. If so, in Telescope Control set dx and dy to something like 50 and move diagonally in the chip. This offset should be now smaller. Try with smaller offsets and cross-check.
    • Avoid the upper-left (NE) quadrant. It cointains spots of dead pixels.
    • If the star is too bright, you may need to defocus slightly the telescope so that it doesn't saturate.
    • In the RetroCam-Control window select the macro by clicking on the Dither button. Then select:
      • Dither-Step = 5" - 15''
      • Dither-Pattern = rot-5
      • Guider = none
    • No guiding is required.
    • Launch a dither sequence by clicking on the Execute button.
    • Change filter and repeat the previous step until you have done Yc, Jo and Hc.
    • Remember to apply the focus offset when changing from Y-H to J.

    3.3 Guiding

    • Guiding is  done automatically by the telescope. Once you're pointing to your target, when selecting the macro on the Dither, choose guider=auto.
      Then the telescope operator will search for a guide star and put it into the guiding box and shall start guiding, and when ready, the observations can start. We have experienced problems while guiding with RetroCam: somtimes the images will look elongated or the guide star will jump out of the guider box. This is why some observers prefer not to use the guider with RetroCam, in which case we recommend setting the number of loops to 1 and repeat the dither sequence until the desired exposure time is obtained.
    • A  SkyMap is available. The TO may use it to find guide stars.


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4. Quick-Processing IRAF Scripts

  • A series of IRAF scripts are available in Rigel and csp4 to help the observations.
  • The scripts are loaded automatically when you start IRAF. The task definitions are given in the '' file in ~/iraf/.
  • The script files themselves sit in ~/iraf/retro_quick/.
  • The following tasks are available:
    • dis:
      Displays an image without having to type in the whole name.
      Usage:    cl>  dis  num   loo
      where 'num' is the frame number, and loo is the loop number.
    • disi:
      The same as above but it starts imexamine.
      Usage:    cl>  disi  num   loo
    • dp:
      Displays the difference between two "_001" frames.
      Usage:    cl>  dp  num1   num2
      where 'num1' and 'num2' are the frame numbers of the images to be subtracted.
    • pdiffi:
      Displays the difference between any loop of two frames and starts imexamine.
      Usage:    cl>  pdiffi  num1  num2
      by default, it subtracts loops "_001" of both frames.
      You can edit the optional parameters 'l1' and 'l2' to use other loops.
    • avgo:
      Displays the difference of two frames after averaging all the loops in each one.
      Usage:    cl>  avgo  num1  num2
      You can modify the optional parameter 'scl' to change the scaling factor to be applied before subtraction --- scl = "mode" is the default.
    • sky_stats:
      Shows the median and mean sky level for a range of frames. Useful to check flats.
      Usage:    cl>  sky_stats  num1  num2
      where 'num1' and 'num2' give the range of frames to analyze.
    • p_fid:
      Mark a fiducial star used to align dithered images.
      Usage:    cl>  p_fid  r  num1  num2  aut/man
      where 'num1' and 'num2' give the range of frames in a sequence. Options 'aut' or 'man' allow to make the program select a star, or the user to mark it. The task will write the star position in the headers of frame num1.
    • p_fx_asecs:
      Correct the RA and DEC offsets between frames that are written in the header keywords ASECS and DSECS.
      Usage:    cl>  p_fx_asecs  r  num1  num2
      where 'num1' and 'num2' give the range of frames in a dither sequence. The user will be prompted to mark the same star in all frames (after averaging the loops). r_quick will usually fail if this is not done in advance.
    • p_mimdel:
      Delete a range of frames of some kind.
      Usage:    cl>  p_mimdel  pre  num1  num2
      where 'pre' is a frame prefix ('icr' for loop-combined, 'isx' for sky-subtracted, etc.), and 'num1' and 'num2' give the range of frames in a dither sequence. Since p_fx_asecs fixes the headers of 'irr' frames only, you will need to delete the 'icr' frames before running r_quick, in order to get the right offsets.
    • r_quick:
      Produce a quick and dirty stack of a range of frames.
      Usage:    cl>  r_quick  num1  num2
      It produces a sky by averaging the frames. It asks the user to mark a few stars with 'a' in imexamine. It may fail if the dither steps are too large (>30''), or if the guider star got lost..
  • To make a fast combination of a dither sequence:
  • rcmosaic: For example, for a sequence of frames 10 to 18  type: 'rcmosaic 10 18' and follow the instructions that will be displayed. You can also go step by step as follows:
  • p_fid r 10 18 aut
  • p_fx_asecs r 10 18
  • p_mimdel icr 10 18
  • r_quick 10 18

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Last modiied on March 27, 2015 by Nidia Morrell (


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