Bruce's sequence and comments about the field photometry file for evaqr: http://ftp.nofs.navy.mil/pub/outgoing/aah/sequence/evaqr.dat should drive home the reason why I observe a field three or more times during an interval of a month or more before I consider the field photometry reliable. Here are the three nights of data for the GSC star: yymmdd HJD V B-V verr bverr 981018 51104.6813 12.351 1.500 0.002 0.001 981019 51105.7201 12.340 1.509 0.002 0.002 980622 51351.9233 12.640 1.442 0.002 0.003 The first two measures showed no variation outside of normal photometric error (the 2millimag error above is unrealistic based on a single datum). However, the third measure was eight months later and the red star had obviously changed in magnitude. If you just observe a field once and consider that you have enough photometry to derive a sequence, you risk both a zero point offset (depending on your nightly calibration) and the inclusion of variables. Arne