scratch exposes the CCD mosaic and saves the images as four runs in FITS files. The files are not passed to the archiving and logging facilities.
The command handles the necessary interactions with the autoguider. At the end of the readout, the shutter opens again to let the autoguider see the sky. If the system is autoguiding at the start of the run, it will autoguide during the exposure and again after the run finishes.
A title may be given for the observation: the title appears as the datum of the OBJECT keyword in the FITS headers.
scratch n exp-time ["title"]where exp-time is in seconds. The title-string must be enclosed in double quotes. n identifies the lowest-numbered scratch file in the set of four: the other three numbers are n+1, n+2 and n+3.
If you choose a number range in which scratch files already exist, those earlier files are overwritten and lost.