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FIES SEQUENCER + STANCAM SEQUENCER observing guidelines

This page is aimed at making observations with FIES, the high-resolution FIbre-fed Echelle Spectrograph, using the SEQUENCER mode.
General information about FIES can be found here.

Startup

Starting FIEStool

Fibers

Target Acquisition

Target Acquisition Hints

Focussing

Obtaining spectra: exposure examples

The exposure meter

Shutdown

Starting the FIES and STANCAM SEQUENCERs

  • On lisa choose tessa in the XDMCP host-menu and log in as user obs .

  • Then open a terminal window and type
        ssh -X verushka
    to login to verushka.

  • Type
        startobssys fies
    and type in the correct TCS accesscode in the popup window.

    This will start the FIES and STANCAM observing software. For each instrument there will be 2 white Sequencer windows where commands can be entered, a BIAS DS9 image display, a beige BIAS CCD status window, a small grey postprocessing UIF, and a blue observing log.

    Aditionally the FIESTA status window, the Sequencer's Talker window, and the TCS Status Display are started. These programs allow to monitor system status.

    Finally a small window with an orange 'handset' is started, which allows to tweak the star towards the fiber.

  • In all the SEQUENCER windows change the working directory to the one assigned to your program, for instance
        cd ~/scripts/38-053
    as in this directory your FIES observing scripts can be found, created, and executed.

  • To activate the observing logs press the 'Load images' button and enter the proper date specification in the FITS file names, for example
        FIrk23*.fits (for the FIES log)
        STrk23*.fits (for the STANCAM log)

    Note that the FIES log can be restarted in a terminal window with
        cd /data/fies
        obslog-fies
    and similarly for STANCAM:
        cd /data/stancam
        obslog-stancam

  • Note that the FIES and STANCAM postprocessing UIFs can be restarted in a terminal window with
        fies-postproc
        stancam-postproc

  • For a list of available SEQUENCER commands type 'help' on the SEQUENCER terminal windows or see See also a list of handy FIES SEQUENCER scripts.

  • Click (twice) on the ScreenShot below to zoom in.

  • As soon as a first frame has been taken with either StanCam or FIES, the postprocessing DS9 image display will pop up. This image display should be used for target acquisition and for examining the frame with imexamine.

Starting the FIEStool reduction software

  • On florence login as user guest.

  • Then open a terminal window and type
        ssh -X fies-pipe@elena "cd datared; ./FIEStool.py"

  • Once FIEStool has started up:
    - choose a mode (normally 'advanced')
    - switch on "Autocheck new files"
    - define a wavelength region to plot
    - and click "START processing"

Choosing the science fiber(s)

For the current fiber bundle C the fibers are numbered as follows:

Fiber correspondence table
fiber 1     low-res, R=25000, 2.5 arcsec
fiber 2 med-res, R=45000, 1.3 arcsec, optional sky fiber
fiber 3 med-res, R=45000, 1.3 arcsec
fiber 4 high-res, R=65000, 1.3 arcsec
fiber 5 high-res, R=65000, calibration fiber

Fiber #5 does not run to the telescope but to a dedicated calibration unit. This fiber provides the ThAr light for the simultaneous-ThAr mode.

There are 8 mask positions; type 'Cntr-I' in the FIESTA status display to see what position number corresponds to what fibers. Moving the mask takes a while.

There are 8 arm positions; type 'Cntr-I' in the FIESTA status display to see what position number corresponds to what fiber/lamp. If you want to take calibration spectra, then you have to put the calibration arm in front of the science fiber.
If you want to take on-sky spectra, then you have to put the calibration arm away from the science fiber!! This means putting it in front of another fiber.

Use the SEQUENCER scripts setup-fibN-star, setup-fibN-halo, setup-fibN-thar (where N is 1,2,3,4) to move the arm and mask in the correct position.

ARM correspondence table
commandposition
arm 1fiber 1 , halogen
arm 2fiber 1 , ThAr
arm 3fiber 2 , halogen
arm 4fiber 2 , ThAr
arm 5fiber 3 , halogen
arm 6fiber 3 , ThAr
arm 7fiber 4 , halogen
arm 8fiber 4 , ThAr

   
MASK correspondence table
commandposition
mask 1fiber 2
mask 2fiber 3
mask 3fiber 4
mask 4none (all closed)
mask 5fiber 1
mask 6fiber 1+2
mask 7fiber 2+3
mask 8fiber 3+4

Target acquisition


Target acquisition with StanCam (camera-probe-fies).
Left: hole 1 (low-res, 200 micron) and hole 2 are open, the calibration arm is at hole 4 (high-res).
Right: hole 3 (med-res) and hole 4 are open, the arm is at hole 1.
The small dark holes are the apertures to the fibers, and are 1.3 arcsec and 2.5 arcsec diameter for the 100 and 200-micron fibers respectively. The goal of target acquisition is to get the star on one of the fiber apertures. The images above were taken with the dome lights on, such that it is possible to see the calibration arm.


A 100x100 pixel StanCam (camera-probe-fies) window around hole 1 (low-res fiber, 2.5 arcsec aperture diameter), with the star 5 arcsec away from the aperture (left) and almost centered on the fiber (right).

 
Essential info for target acquisition:

Fiber positions for camera-probe-fies
fiberCCD X-posCCD Y-pos
1 low-res 496147
2 empty 479318
3 med-res 491489
4 high-res524656
Fiber positions for camera-probe-stancam
fiberCCD X-posCCD Y-pos
1 low-res 4401020
2 empty 410790
3 med-res 430580
4 high-res470330

  • Image scale on Stancam with camera-probe-stancam: ~0.18 arcsec/pixel
  • Image scale on Stancam with camera-probe-fies: ~0.24 arcsec/pixel
  • Approximate telescope focus with camera-probe-fies : 23???
  • Approximate guide-tv focus with camera-probe-fies: 550
  • Approximate FOV diameter of holes in fiber mask: 20 arcsec
  • Approximate diameter of hole in mirror of the low-res fiber: 2.5 arcsec
  • Approximate diameter of holes in mirrors of the med- and high-res fibers: 1.3 arcsec

  • Field orientation for 'field-rot = 0' on the Stancam movie with camera-probe-fies:
    Field orientation


    S


    W
    E


    N

  • Step sizes between fibers for camera-probe-fies.
    Teloffset between fiber positions for camera-probe-fies
    DirectionCommand
    from fiber #1 to #3 stancam.teloffset 2 83
    from fiber #1 to #4 stancam.teloffset-6 123
    from fiber #3 to #1 stancam.teloffset-2 -83
    from fiber #3 to #4 stancam.teloffset-8 40
    from fiber #4 to #1 stancam.teloffset 6-123
    from fiber #4 to #3 stancam.teloffset 8 -40

     
    Acquisition hints:

    1. To setup the telescope for FIES run the following script after switching on the telescope power, or after using other instruments for science exposures:
      FIES/STANCAM SEQUENCER window: setup-tel-fies
      Note that steps 2-4 below are already done as part of the setup-tel-fies script.

    2. TCS terminal: foc-pos 23xxx (the default focus for FIES)
    3. TCS terminal: ccd-filter 2 (put in blue STANCAM filter or else 3, 4, or 8)
      Note that you have to use a clear or BVR filter, or else the fiber entrance will not be in focus on StanCam.
    4. TCS terminal: field-rot 0

    5. slew the telescope to target, and start guiding.


      The commands of steps 6-12 below are grouped together in the script stancam.acquisition.

    6. setup the mask and arm for fiber number N.
      FIES/STANCAM SEQUENCER window: setup-fibN-star   where N is 1,2,3,4

    7. FIES/STANCAM SEQUENCER window: camera-probe-stancam (to go to STANCAM imaging mode)
    8. take a full frame image with Stancam (e.g. binned by 2). The image will be grossly out of focus, but that does not matter.
      STANCAM SEQUENCER window: autosave_on
      STANCAM SEQUENCER window: resetxy
      STANCAM SEQUENCER window: bin 2
      STANCAM SEQUENCER window: exp 0.1 (or longer for faint stars)
    9. move the star close to the projected X,Y coords of the fiber of choice (see top of this page), using the fiboff routine:
      STANCAM SEQUENCER window: fiboff N   where N is 1,2,3,4,
      which uses the postprocessing DS9 display, and follow the instructions.
      After the telescope moved, press 'q' in the postprocessing DS9 window to stop the fiboff routine.

    10. FIES/STANCAM SEQUENCER window: camera-probe-fies (to go to fiber viewing mode)
    11. switch on STANCAM 'movie mode'
      STANCAM SEQUENCER window: fibNmovie exptime hicut   where N is 1,2,3,4, exptime∼0.5, and hicut∼1000
      Note that you can tune the colour cuts while the movie is ongoing, using the Sequencer commands hicut, locut, and zscale.
    12. and use the orange guide-probe offset keys to move the star onto the dark spot (= fiber)

    If you have to start at step 1 then the whole process can take about 10 minutes. Experienced users will manage to do target acquisition in less than 3 minutes.

    Focusing

    For FIES the telescope should be focussed while in fiber-viewing mode (camera-probe-fies). The default telescope focus for FIES is 23???, which usually gives good results. Hence the below instructions are only for the sake of completeness.

    Focusing instructions:

    • First move a bright star (e.g. an FK5 star) onto the fiber.
    • Preset to the star and start guiding.
    • Go through the steps of the above acquisition hints.

    • Switch on the postprocessing tool QuickExam.
    • Then take a few spectra with FIES, with different values for the telescope focus; a good focus step is 50 units. Use the postprocessing tool QuickExam with keystroke 'l' to find the telescope focus that gives best throughput on FIES.
    • Set the final focus based on the best result obtained from the above sequence, for example
      TCS terminal: foc-pos 23xxx

    Making target and calibration exposures: short guidelines

    When you have the target on the fiber, and have autoguiding switched on, you can either expose on the target or take calibration frames.
    How to make exposures on-target (in FIES SEQUENCER window):

    This is an example of a frame (only the central part is shown) obtained in simultaneous-ThAr mode.


    Calibrating the science fibers:

    The special SEQUENCER script called fies-calibs can be used to automatically obtain a full set of calibration images in the afternoon and in the morning.
    Alternatively, the SEQUENCER scripts setup-fibN-halo, setup-fibN-thar, or exp-fibN-halo, exp-fibN-thar can be used to simplify the calibrations.

    Below are some basic commands to make calibration images.

    • Halogen flat:
      • setup-fibN-halo   (where N stands for 1, 2, 3, or 4)
      • object Halogen
      • expose X               (where X stands for the number of exposure seconds)
      • lamp 6 off

    • ThAr calibration:
      • setup-fibN-thar   (where N stands for 1, 2, 3, or 4)
      • object ThAr
      • expose X
      • lamp 7 off

    • Change back to on-sky observing:
      • setup-fibN-star   (where N stands for 1, 2, 3, or 4)

    • A table of typical exposure times for the calibration frames can be found here.


    Simultaneous-ThAr mode: science exposures and calibrations

    For this mode there is a special SEQUENCER script called simulthar to automatically allow some ThAr light into fiber #5 during a science exposure, at fixed intervals.

    The special SEQUENCER script called fies-calibs can be used to automatically obtain a full set of calibration images, including a minimal set of 1 ThAr and 1 halogen both through fiber #5.
    Alternatively, the SEQUENCER scripts setup-fib5-halo, setup-fib5-thar can be used to simplify the calibrations.

    Required calibration: to trace the ThAr spectrum you need a separate flatfield exposure with fiber #5.

    Required calibration: to calibrate the wavelength offset between the science fiber and the calibration fiber #5 you need an exposure with both ThAr lamps switched on. This will give a 'double' ThAr spectrum.

    Below are some basic commands to make calibration images.

    • Halogen flat:
      • setup-fib5-halo
      • object Halogen
      • expose X               (where X stands for the number of exposure seconds)
      • lamp 1 off

    • ThAr calibration:
      • setup-fib5-thar
      • object ThAr
      • expose X
      • lamp 4 off

    • Double ThAr calibration:
      • setup-fibN-thar   (where N stands for 3 or 4)
      • setup-fib5-thar
      • object "double ThAr"
      • expose X
      • lamp 4 off
      • lamp 7 off

    • A table of typical exposure times for the calibration frames can be found here.

    The exposure meter

    Since fall 2008, FIES is equiped with an exposure meter that can be used to monitor the count rates during an ongoing exposure. The exposure meter picks off light inside the spectrograph that otherwise would have fallen outside the bottom of the CCD. As the red orders are longer than the blue orders, and hence more red light is falling off the CCD, the exposure meter is more sensitive for red stars than for blue stars.

    Use the FIES exposure-meter count calculator (EMCC) to find out what is the exposure-meter count value that corresponds to the required peak S/N in the FIES spectrum of your star.

    The most useful Sequencer commands to operate the exposure meter are the exposure command 'exp-count', and the counter commands 'expmcount' and 'expmstopcount'. For example, to expose an M star to reach CCD counts peaking at approximately 32000 ADU, which corresponds to a peak S/N=sqrt(32000*0.7*4)=300, the EMCC tells you that 50 million exposure-meter counts are needed. Then use the command
        exp-count 50000000 1800
    which will readout when the exposure meter has reached 50,000,000 counts or when 1800 seconds exposure time have elapsed.
    Above the expected S/N per extracted spectral bin is computed as S/N=sqrt(peak-ccd-counts * ccd-gain * profile-width), with the profile width 7 pixels for the low-res fiber and 4 pixels for the other fibers. See the FIES EMCC.

    The dark current of the exposure meter is on the order of 150 counts per second, and has not been accounted for in the exposure-meter count calculator.

    The exposure meter counts and count rates can be monitored graphically on a separate page of the FIESTA window.

    Unfortunately the exposure meter cannot yet be used with the simultaneous ThAr mode.

    Shutting down

    • Turn off all the lamps, e.g. 'lamp 1 off', etc.

    • Open a terminal window as obs@verushka and type shutdownobssys fies






  • Back to top Last modified: 18-Nov-2014