14 | QUIRC User Guide |
dither subtract on/off This option, when turned on, will subtract the previous image from the current one and store the result in a file with a “chop" added to the normal data file name instead of the file number. The name is the same as the chop mode described above. This is often useful when dithering on a faint source that cannot be seen without subtracting the sky/array background from the image.
For experienced users: note that if you want to use auto from a script, you can specify the complete set of parameters, in the order above, as numeric arguments. Be careful not to skip any, and use 1 for on and 0 for off.
clear h[num]iClear (reset) array
clear resets the detector num times, default 1. If you have
comment htextiAdds a comment to the obs.log file, and to the FITS header of the
>image file. This is added only to the next observation header, then it is cleared.
et hsecondsiSet exposure time
et sets the exposure t me. Any floating point value is accepted; the accuracy of the exposure timing is somewhat better than 0.01 second, but it is ultimately limited by the mechanics of the shutter. et uses Unix to compute the exposure time, and an exposure which is based on Unix t ming can be interrupted. Some care is taken to make sure that the unix timed exposures are correct, but the machine running qcdcom is heavily loaded it is possible for the shutter to stay open slightly longer. The exposure time recorded in
>the header, however, will reflect the true amount of time the shutter was open.
filter hnum commandiSet filter
This command selects the filter setting. If no filter setting number is given, the list of installed filters and the current setting is given. To specify a filter setting, its number is given. If it is different than the current filter setting, the wheels are moved to the new position. Note that for a filter wheel setting, both wheel positions are specified and the movements are done simultaneously. See the fw command description below if other filter wheel motions are required. To reinitialize the filter wheels, the command fi home is used. One can use fi home1 or fi home2 to reinitialize only one particular wheel. To use the polarizer (wheel 2 position 8) with one of the filters in wheel 1, one adds the word “pol" after the number requested, e.g. fi 1 pol will select filter setting 1 and the polarizer instead of the OPEN position in wheel 2. Since the polarizer is in the second wheel, it can only be used with filters that are in wheel #1 (filter settings
The command fi DARK will move the filter 1/2 filter step backward between filters to aid in taking a dark frame if necessary. Note that there is now a LOWFLUX filter setting which should give a reasonable dark frame. The command fi BACK inverts the DARK command and restores the wheel to its previous position. Be very careful to issue BACK when finished taking dark frames, otherwise the filter wheel position will be lost. If this happens, more than one DARK or BACK command in a row or not in pairs are issued, or the filter wheel motion fails for any reason, issue a filter home command to
