[Aavso-photometry] xform question

[Michael Koppelman]

So when we do our transformation coefficients we end up with basically 
a slope coefficient and an intercept coefficient for each 
transformation. In theory the slope coefficients don't change much over 
time for a given telescope/camera/filter combination. The zeropoint, 
though, which needs to be determined each night, is basically the 
intercept coefficient, right? The question I'm leading up to is: you 
don't really use the intercept coefficient that you calculate when you 
are calculating your slopes, right? When you actually transform unknown 
fields you just use the slopes and the zeropoint, right?

I'm thinking a guy should also use weighted fits when determining these 
coefficients as well?

For me my slope coefficients after 8 nights over 2 years are:

Vr      0.017  (V from V-R)
Vb      0.007  (V from B-V)
B-V     1.060
V-R     1.097
R-I     0.947
V-I     1.016

Cheers,
Michael Koppelman
http://www.lolife.com/astronomy/