Scattered Red Light in the FOS
W. P. Blair, A. F. Davidsen, and A. Uomoto

The Johns Ifopkins Universiiy

DRAFT Instrument Science Report CAL/FOS058 DRAFT

Eebruary 1989

ABSTRACT
Continuum laxnp observations have been used to determiue the fraction
of iricident long-wavelength photons scattered into the ultraviolet
bearn by the. FOS dispersers. Except for the relatively unh4~e1y
conbination of the G16OL grating and red Digicon, the gratings sho.w
acceptable scattered light level~of ~bøut OÄJ2% ofthe peak red light
intensity. Observatipns with the: pr-ism indicate a potentially high
suscepctihty to scattered red light (up to 1%), although the test
exposures were heavily overexposed and thi~ nurnber is. highly
uncertain.