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This article describes the control of the electronics and calibration lights of the ACE spectrograph. Note that this article does not cover the control of the telescope itself and the auxiliary devices used in parallel with the spectrograph (namely, the on-axis fiber camera, its control and the autoguiding process of the telescope).

General commands and usage

The spectrograph can be controlled with the program acectrl. For detailed help, type

acectrl --help. 

This command prints the available set of command line arguments with which the spectrograph can be controlled:

@m5:~$ acectrl --help
Usage:  acectrl [-h|--help] [-v|--verbose]
        [-c|--device|--connect <address>:<port>]
        [--thar-lamp on|off]
        [--flat-lamp on|off]
        [--led <intensity_between_0_and_1>]
        [--mode science|thar|flat|aux]
        [--fiber-focus [+|-]<focus>]
        [--spectrum-focus [+|-]<focus>]
        [--spectrum-reset] [--spectrum-preset-focus <focus>]
        [--guide-xstage-reset [--guide-xstage-center]]
        [--guide-focus [+|-]<steps>]
        [--filter-[1|2] {0|1|2|3|4|5}]
Some remarks or notes:
        - Default device <address>:<port> is
        - Before changing modes or doing focusing, start the spectrograph.
        - Stopping or starting spectrograph does not turn on or off the lamps.
        - '--xxx-lamp' just truns on or off the lamps and does _nothing_ else.
        - '--mode xxx' also turns on or off the lamps: use mainly this feature.
        - Many `acectrl` instances may interfere, please be aware of this fact!

The current status of the spectrograph can be displayed with the

acectrl --status

command. It will result in a following output:

# Frontend:
    Main pickoff mirror:    off  
    Fiber (WATEC) focus:    870
    Calibration fiber arm:  3 (mode: science)
    Guider focus position:  2100
    Guider X-stage offset:  58000
    Filter wheel #1 (V, lower): slot 1 (idle) 
    Filter wheel #2 (R, upper): slot 0 (idle)

# Calibration lamp mount:
    Rotator axis:        500 (unknown/none) 
    ThAr lamp:      off
    Flat lamp:      off
    Led illumination:    off (0.0000)

# Bench:
    Spectrum focus:      11700

The state of the Main pickoff mirror indicates whether the spectrograph is turned on or off. The spectrograph can be turned on or off with the

acectrl --start|stop 

command. The Calibration fiber arm field indicates the current spectrograph mode. It can be changed with the

acectrl --mode thar|flat|science 

command. Note that while the thar and flat modes turn on the necessary calibration lamps, changing back to science mode does not turn them off. The lamps can be controlled separately with the

acectrl --thar-lamp on|off
acectrl --flat-lamp on|off

commands. Also, turning on the spectrograph does not change the spectrograph mode to science, so do not forget to check the status. The x-stage guider should be checked as well, especially after a power failure, as it is possible that the guider lost its home position. It can be fixed with a acectrl --guide-xstage-reset and acectrl --guide-xstage-center command sequence.

The focii of the off-axis guider, the on-axis fiber cam and the collimator optics on the spectrograph bench can be controlled here as well. After starting the spectrograph, default values are set (with the exception of the collimator opcics), but these should be verified or fine-tuned. A LED placed in the spectrograph front-end can be turned on with the

acectrl --led n

command (where n is a number between 0 and 1 indicating the intensity of the LED) to help focusing the on-axis camera. To focus the collimator optics, a practical way is to obtain ThAr calibration maps, and check the peak intensity while fine-tuning the focus value.

Note that the focus of the telescope can be adjusted from ccdsh on the regular way:

set focus n

where n is the focus value. For the spectrograph, the default is around 81.2.

For obtaining ThAr calibration frames, the optimal exposure time is 1-2s, while for flats it is around 10s.

Starting observations

In order to start observing with the ACE spectrograph, do the following.

  • Initialize the FLI ML1109 bench camera camera properly via the CCDSH session that also controls the telescope.
  • Check the status using acectrl --status. This command should promptly (within a fraction of a second) provide the status information.
  • Start the spectrograph using acectrl --start.
  • Set the spectrograph mode appropriately. Probably you would start with taking a few ThAr spectra, so use acectrl --mode thar. Starting with some ThAr spectra can easily check whether the bench collimator optics is in focus and such spectra can also be taken while waiting for the bench camera to completely be cooled down.
  • If the ThAr spectra are slightly out of focus, use acectrl --spectrum-focus [+|-]step to fine-tune in the focus position. If the ThAr spectra are completely blurred, reset the collimator focus using acectrl --spectrum-reset and then start tuning with the focus. Don't forget to explicitly specify the sign of focusing steps!
  • If the camera is cooled, take same ThAr spectra and save them. Use exposure times between 1...5 seconds.
  • In a single run, never change the bench focus position once set properly.
  • Turn the spectrograph into scientific mode with acectrl --mode science.
  • Turn on the auxiliary LED on by acectrl --led 0.7.
  • Watch the live image of the on-axis camera. If needed, adjust focus of the on-axis fiber camera optics with acectrl --fiber-focus [+|-]step
  • Turn off the auxiliary LED on by acectrl --led 0.
  • In a single run, never change the focus of the fiber camera optics once set properly.
  • Start the telescope sidereal tracking and slew the telescope to the desired position. Use the CCDSH focusing command set focus ... to focus the telescope in order to have a sharp image on the on-axis fiber camera.
  • Tweak the telescope position (using CCDSH or the program `rccpanel`) in order to move the target star behind the fiber.
  • Start autoguiding if needed (it is recommended to do autoguiding if exposure times are longer than a few minutes).
  • Take spectra.
  • Take ThAr spectra regularly. The frequency of such spectra depends on the scientific accuracy needed by the actual observations. In general, the larger the thermal stability of the bench, the less frequent the ThAr spectra have to be taken.

Stopping observations

The following series of commands should be executed

  • Turn the spectrograph into scientific mode with acectrl --mode science. This command will also switch

off the ThAr lamp and flat lamp if these were turned on berfore.

  • Also ensure that the auxiliary LED is switched off with the command acectrl --led 0.
  • Check the status with acectrl --status. The above two commands ensure that no light sources are left turned on and hence the spectrograph frontend box is completely dark. This is essential if alternate instrumentation mounted below the frontend box is going to be used.
  • Turn off the spectrograph with acectrl --stop.

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