Nod is useful for moving between target and sky positions. To help with recordkeeping, exposures at the starting position are all made with selection one in the data-taking system, while all those made at the offset position use selection two . The user is prompted for a single set of right ascension and declination offsets, in arcseconds, which define the distance between the start and offset positions. The user is prompted for the number of exposures at each position, the number of iterations of the sequence, and whether the program should pause before and after moves, to allow enabling or disabling of the autoguider. Remember that with n coadds selected, each exposure is the sum of n frames.
Dither moves the telescope according to a predetermined pattern.
In the first three cases below, the user is prompted for the number of exposures at each position, the number of iterations of the entire sequence, and whether the program should pause before and after moves, to allow enabling or disabling of the autoguider. The telescope always returns to its starting position on completion of the observations. Exposures are made according to the parameters in selection one of the data-taking system. Remember that with n coadds selected, each exposure is the sum of n frames. To protect your own dither files from being accidentally overwritten, save a copy in your personal directory.