STIS Filters and Dispersers

Note that MAMA imaging observations are subject to especially strict bright object limits, and will not be performed unless ALL objects in or near the aperture can be shown to be below these limits.

As STIS filters are located in the STIS slit wheel they are listed as apertures in Phase II proposals and cannot be used in combination with other apertures. The STIS filters can, however, be used together with a grating to do filtered slitless first order spectroscopy. This can be especially useful when it is necessary to exclude contamination due to geocoronal lines.

STIS has a relatively limited set of filters. However its imaging capabilities do include some unique advantages that make it worth considering as an alternative to WFC3 or ACS for some UV and optical imaging projects.

Comparisons of Imaging Mode Throughputs

Choosing a filter for imaging observations or slitless spectroscopy

STIS Brightest Pixel EE table with narrow slits

For narrow rectangular slits (e.g. 52X0.05), the size fed into the enclosed energy table for brightest pixel calculation is less than one pixel in one dimension (1X0.68), but is interpreted as a 1X1 pixel area. This will cause the count rate reported for the brightest pixel to be over-estimated. Since the brightest pixel is only used for rate limit checking, it should have no effect unless the observation is producing results close to the count rate limit.