Standard stars
M67 Dipper Asterism
The Dipper Asterism in the open cluster M67
contains a a photometric
color sequence, and hence serves as a convenient field for photometric
calibration. Stars forming a photomeric sequence are marked below and
their BVRI magnitudes can be found in
Chevalier, C & Ilovaisky, S.A. 1991, A& AS, 90, 225
Landolt standard stars
Landolt, A.U. 1992, AJ, 104, 340