The following sources provide data on stars
suitable for photometric calibrations. Remember that for short exposures
the variation in the shutter "fly time" may dominate the photometric accuracy
of your result. One way around this is to define a set of "secondary"
standards in the field which are relatively fainter than the standards
given below. A short (say, 1 second) exposure may give a good exposure
on the primary standards, and sufficient exposure in a number of fainter
field stars. Then a longer (say, 10 second) expsoure will still leave
the fainter stars unsaturated, but will have only a fraction
(1/10 in the example given) of the uncertainty due to variation in the
time it takes to open and close the shutter. The ratio of fluxes of the
faint stars in the short and long exposures is also the ratio of the
effective exposure times of the two exposures, allowing you to infer a more
accurate exposure for the first, short exposure. This then allows a more
accurate calibration of the primary standards. Note that as long as the
exposures are taken with the same filter there is no need to know the colors
of the fainter field stars (the "secondary" standards).
- UBVRI photometric standard stars in the magnitude range 11.5-16.0 around the celestial equator
- Landolt, A. 1992, AJ, 104, 340
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