"To convert the instrumental measurements of the binary separation and PA into celestial units, we used a weighted average of the calibration from Pravdo et al (2006, ApJ, 649, 389), with a pixel scale of 9.963 ± 0.011 mas/pixel and an orientation for the detector's +y axis of -0.13 ± 0.07° east of north. These values agree well with Keck Observatory's notional calibration of 9.942 ± 0.05 mas/pixel and 0.0 ± 0.5°, as well as the 9.961 ± 0.007 mas/pixel and -0.015 ± 0.134° reported by Konopacky et al (2007, AJ, 133, 2008). Also, comparison of NIRC2 images of M92 to astrometrically calibrated HST/ACS Wide Field Camera images gives a pixel scale for NIRC2 that agrees to better than 1 part in 1000 with our values (J. Anderson, priv. comm.)."