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Data acquisition

We are now ready to start observing. The target object has been acquired and put on the slit, and a guide star found. We start taking data with

ADAM> RUN 1000 "target 1234 1000s"

The cosmic ray rate is typically 20-30 events per full CCD frame per 1000 seconds. These can be weeded out of the sky areas by the reduction software, but if they land on the object spectrum you can only clean them out by comparing with another exposure. For this reason, it is best to limit exposures to less than 1800 seconds. There is an overhead of about 30 seconds while the chip is read out and the image displayed before you can issue another RUN command. As the sky alone generates between 200 and 1000 adus per pixel per 1000 seconds, FOS is mostly well above the readout noise problems in typical exposure times.

All of the normal CCD commands are applicable to FOS, and so the observer is referred to the CCD userguide, which is kept in the INT control room.

Tue Apr 12 04:13:28 BST 1994