October 30, 1997 | 7 |
4 Writing Scripts and Taking Mosaics
Any sequence of qcdcom commands can be entered into a text file (using your favorite editor) and executed by qcdcom. The command to do this is source file, where file is the filename of the command list. This allows some routine types of observations to be performed automatically, for example taking a sequence of images in J, H, and K. By entering a sequence of filter move, exposure time, and go commands into a file, taking a JHK sequence can be done with one source command. Each command is printed along with its file name and line number before it is executed. If some command in the script fails, execution will stop and the line number where it stopped is printed. A script may be
Scripts can be most useful for taking mosaics, by using special commands to move the telescope and communicate with the guider. If you are taking a sequence of unguided exposures, such as for standard stars, the telescope may be moved directly; the command to do this is tel aoffset RA Dec, where RA and Dec are offsets from the base position (88”) or current telescope position (CFHT, 0.6m). These commands can be interspersed with go commands, filter changes, etc. in a script to perform whatever pattern you wish.
You can also perform “guided” offsets, either directly (CFHT) or through communication with Atlas (88”). This is done via the tel goffset RA Dec command, which stops the guider, moves the telescope and guide probe, and turns the guider back on. On the 88" this communicates with Atlas and MiniOtto over the ethernet to perform the guider movements, and on CFHT commands are sent over a serial cable to the TCS.
As an example, a potentially useful script is one that takes data for a standard star. This might be a sequence of exposures in a dithered pattern (using alternating tel aoffset and go commands), followed by a filter change, followed by another dither pattern, and so forth. Several example scripts may be found in the home directory of obs/irgroup. Another useful script is one that takes a standard dithered pattern of a field (e.g. a
If you prefer, it is also possible on the 88" to run mosaics from Atlas. To do this, turn pause and CCD modes off and QUIRC mode on on Atlas. After initiating the mosaic program on Atlas, the qcdcom tel gnext command tells Atlas to move to the first mosaic pattern position and waits for it to finish moving. The go command can then be issued, then another tel gnext causes Atlas to move to the next mosaic position. This can be repeated until the mosaic is complete, and any other qcdcom commands (except telescope motion, do not use aoffset!) can be interspersed. Note that if Atlas encounters an error, an alert box will pop up and Atlas will cease talking to qcdcom until the alert is cleared. This will most likely cause the script to fail, and the mosaic will need to be
5 Filters and Focusing
There are now two filter wheels in QUIRC with eight positions each. Because two OPEN positions (position 5 on both wheels) are required and one position (wheel 2 slot 8) holds a polarizer, thirteen