GHRS Instrument Science Report 076 "Photocathode Granularity Maps for Grating G140L of the GHRS" A. Schultz and J. Eisenhamer Aug 12, 1996 Abstract Maps of photocathode granularity have been created for correcting observations made with GHRS grating G140L. These flat fields were computed using a "tomographic" technique to separate spectrum from granularity features using observations of BD+75D325 taken on September 22, 1995, as part of program 6209. Application of the flat field to G140L observations taken after the 1993 HST Servicing Mission indicate that the flat field corrects features at the 2% level for observations with signal-to-noise greater than about 30. The technique discussed in this ISR to create the G140L flat field can be used with care to create flat fields for other GHRS gratings.
