A method for determining the V magnitude of asteroids from CCD images

摘要

We describe a method of determining the V magnitude of an asteroid using differentialphotometry, with the magnitudes of comparison stars derived from Carlsberg MeridianCatalogue 14 (CMC 14) data.The availability of a large number of suitable CMC 14 starsenables a reasonably accurate magnitude (±0.05 mag) to be found without having toresort to more complicated absolute or all-sky photometry. An improvement in accu-racy to ±0.03 mag is possible if an ensemble of several CMC 14 stars is used.This methodis expected to be less accurate for stars located within ± 1 0 of the galactic equatorowing to excessive interstellar reddening and stellar crowding.