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.