8.5 Parallel Observations While Using COS
Because the COS aperture is small, it makes sense to use COS as the prime instrument even if a camera, say, is used in parallel. Also, COS is intended to be used on point sources that are centered in its aperture, and that may prevent dithering any camera exposures obtained in parallel. However, small displacements (up to 0.3 arcsec on either side of the center) in the cross-dispersion direction should allow some movement of the image at a camera without degrading the COS spectrum and with only slight loss in throughput.
Proposers with an interest in developing parallel observations with COS are urged to contact an Instrument Scientist and to check the STScI Web pages for new information before the proposal deadline. Also, the HST Call for Proposals should be consulted for policies on using COS in parallel with other instruments.
