Up: General Principles of Observing with CCDs
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  1. Log in, initialise software

    At observer's console

    SI (initials),n,n (n = account, n = Password (same as n))


    and follow prompts. Note that it is most efficient in terms of observing time to put data onto DISK only, and save it on TAPE later using FITSOUT. This can be done during long (> 300 second integrations) so that is perfectly possible to have all your data safely dumped to tape by the end of the night. The EAGLE disk can theoretically hold more than 1200 CCD frames which is more than adequate in most cases for a week's observing. However you are strongly recommended to dump to tape as soon as convenient. Power cuts have drastic effects on large disks.

    Initialise the filter wheel by typing ZEROSET in response to an Adam:> prompt.

  2. Hardware set-up OK?

    Cryostat filled and cold?

    Correct filters, filter wheel, optical thicknesses

    Chip orientation correct?

    Telemetry OK?

    Telescope pointing checked, SNAFU?

    Telescope in focus? (FOCUS, SETFOCUS)

    MIMIC display active?

  3. Set filter required

    Adam:> FILTER <name>

    Adam:> FILTER? (displays which filter position is in beam)

  4. Set telescope to flat field position

  5. Set telescope to focus star position

  6. Check positioning, exposure required with a short exposure using

    Adam:> GLANCE (sec)

    This run can be saved with

    Adam:> KEEP ``HD123 10 SECs V FILTER``

  7. Make the real exposure

    Adam:> RUN (sec)

    This command makes the exposure, reads out the chip, displays the image on ther Lexidata with auto-scaling and saves the image file on disk, tape or both, depending on the option chosen. Useful commands during RUN are RUNSTATUS to tell you how long to go; STOP, which terminates and saves normally, just as if requested time had expired; ABORT, which closes the shutter, and loses the data and TIME (sec) which resets the requested exposure time and PAUSE (to stop exposure temporarily) and CONTINUE (to restart a PAUSEd exposure).

  8. To examine the data (best done from the point of observing efficiency after the next run has been started), use:

    Adam:> PHOT

    Follow instructions/indications on the Lexidata and the joystick box. To display and examine other runs:

    Adam:> DISP R(run number)

    Some on-line analysis is available; see II.4. For general file-handling see II.5.

  9. The use of the grisms and the drift scan table can be found in Sections III.3.7 and III.3.8.

  10. Remember to do a few bias frames each night. One long dark frame will be sufficient for the whole run. Dark runs must be done in darkness. Even though the cryostat is reasonably light-tight the dark count is so low that it is swamped by the smallest leak. Always keep the black skirt over the cryostat and filter wheel assemblies for DARK runs and twilight flat fields. If you are trying to flat field through a narrow band filter then white light coming through a leak can swamp the small amounts of light penetrating the filter. Try to get flat fields at the end of the night which will give extra S/N when combined with those at the beginning.

  11. Note that there is no preflash available for the RCA chip. The GEC is regarded as being good enough that preflash is not necessary.

  12. At the end of the session (or preferably during the night) write out data files to tape using

    Adam:> FITSINIT (follow prompts - for new tapes only - do not use on tapes which already contain data)

    Adam:> FITSOUT (follow prompts)

    Dumps from disk to tape with verify option selected take about 50 seconds so it is convenient to write a few at a time during long exposures.

    You can make your data safe by

    (i) Using the VERIFY option on FITSOUT and

    (ii) dismounting the tape from the deck and removing the write ring.

    Please place completed D tapes in the tray marked ``FOR DUTY OFFICER COLLECTION'' together with a copy request form giving details of what is required. Duly copied C tapes for your use will appear in the TAPES COPIED pigeon hole in the INT building on the first floor together with a short listing of the tape contents. Please note that IT IS STRICTLY FORBIDDEN FOR OBSERVERS TO TAKE D-TAPES FROM THE MOUNTAIN.

  13. At the end of the session, sign off:

    Adam:> SHUTDOWN

    and after system messages, request a hard copy of the log file or not.

    *SO (sign off)

  14. At the beginning and end of every night, fill up the cryostat with liquid nitrogen. Your support astronomer or duty tech will show you how to operate the dewar containing the bulk liquid nitrogen supply

Up: General Principles of Observing with CCDs
Previous Page: Control of the Autoguider
Next Page: CCD Data Acquisition Software

Fri Jun 10 17:31:56 BST 1994