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Hubble Space Telescope
FOC Instrument Science Report # 81

FOC Instrument Science Report # 81  		5 Oct 1994

"Cycle 4 Verification of the FOC f/96 Aperture Location"
by W. Hack

Abstract excerpted from the report:

Observations were taken on 5 September 1994 to verify the
location of the f/96 aperture. The PDB was updated in early
June to correct for an error in the f/96 aperture location
since SMOV. These observations were designed as a quick check
to verify the accuracy of the new PDB coordinates. Three
snapshots centered on astrometric stars in the NGC-188 cluster
were taken. Despite minor errors in the target coordinates, the
aperture's ref-erence position was found to be (V2,V3) =
(242.9329, 135.2735), compared to the PDB value of (V2,V3) =
(242.9714, 135.2052). The scatter in the observed positions of
the stars provides a mean positional error of 0.10" in the
aperture reference position.