FOS Instrument Science Report # 101

"Removal of Straylight in FOS Observations"
by Ellyne Kinney and Roberto Gilmozzi

Abstract excerpted from the report:

The FOS suffers from a straylight problem that is especially apparent in
observations of late-type stars taken in the 1150-2100A region.  Flux 
calibrated observations of these objects show an artificial increase in flux in 
the shorter wavelengths.  The problem is easily seen when comparing 
observations with observations from other instruments such as the HRS.  Since
the UV flux from late type stars is very weak, the presence of straylight from
the optical part of their spectrum often completely swamps the spectral features
of interest, making it very difficult to detect them over such an abnormal
background.  In order to provide a way to estimate the amount of straylight
to be expected (so that exposure times can be adjusted to yield the appropriate
signal to noise for the spectral features one wants to study), we have
developed a very simple 'model' for this effect and used it to predict the
amount of straylight in actual observations.


For more information, please contact the above authors.