Estimating Straylight Levels in the Faint Object Camera

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Session 113 -- HST, UIT and UV Instruments, UV Processing and Archives
Display presentation, Saturday, January 15, 9:30-6:45, Salons I/II Room (Crystal Gateway)

[113.01] Estimating Straylight Levels in the Faint Object Camera

E.K.Kinney (STScI), R.Gilmozzi (STScI/ESA)

The FOS suffers from a straylight problem that is especially apparent in observations of late-type stars, taken in the wavelength region of 1150- 2100 \AA. Observations of this kind show elevated flux levels in the shorter wavelength regions. It has been proposed that the increased flux is due to grating scatter. It is possible to estimate the amount of excess light due to this effect based on the target's magnitude, spectral type, and color excess. This method assumes that the amount of straylight detected is constant accross the entire diode array. A curve of predicted counts/second/\AA versus spectral type was constructed, using observations from an independent source, which were used to determine the total amount of light the instrument detects, and an observation with straylight present, which was used to zero the curve.

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