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Hubble Space Telescope
FOC Instrument Science Report # 83

FOC Instrument Science Report # 83              21 Feb 1995

"The Photometric Accuracy of the FOC" 
by Gerhardt R. Meurer

Abstract excerpted from the report:

A comparison is made between the expected photometric accuracy
of the FOC, and that observed. The presently known systematic effects
are listed and quantified. Typically when both internal and external
factors are included one only expects to obtain photometry accurate to
~0.2 mag in the ultraviolet. This expectation is tested by comparing
magnitudes extracted from F220W images of nine starburst galaxies with
those extracted from IUE spectra. After removing one discrepant
observation, it is found that relative to the IUE, the FOC external
errors are 0.05 mag, three times lower than expected. By carefully
removing some of the internal zeropoint variations, one should be able
to reduce the total systematic errors to ~0.10 mag.