The Magnitude scale was derived from a virtual comparison star
and is only an approximation for V mag.
A good comparison star
system is HR 8799, which has four known planets that sweep up the space between two similar disks of debris.
The brightness of each was compared with that of two supposedly constant stars, the comparison star
and the check star that were close on the sky to the variable star.
The sixth column of Table I lists the comparison star
used for each measurement.
Due to a problem with the comparison star
the data were not analyzed.
The B, V, R and I measurements of NGC 7027 were usually made first which was then followed by B, V, R and I measurements of the comparison star
Mu-Leonis was the comparison star
and Epsilon-Leonis was the check star for all magnitude measurements.
02 magnitudes when using a calibration method involving the Canopus add-on, Comparison Star
Selector, which picks comparison stars
of similar colour and magnitude to the target star.
Each measurement consisted of the sequence CSCSCSKC where C is the comparison star
measurement, S is the Saturn measurement and K is the check star measurement.
For eclipse 1, alpha Bootes was the comparison star
, while alpha-Lyrae was the comparison star
for eclipse 2; star magnitudes are listed elsewhere (5).
The comparison star
for all measurements was iota Geminorum; the magnitudes were taken from Iriarte et al.
08 V magnitude comparison star
(TYC 3991-1480-1) together with a 10.