I am using BSM NM and VPhot contains preloaded values for the Transformation Coefficients for this setup:
Tv = -0.010
Tbv = 0.990
Tvi = 0.994
Tvr = 1.001
Tri = 0.968
Arne also kindly supplied the value of Ti (=0.002), which I entered using the manual input box as required.
VPhot then seems happy and can transform my (BVI) observations.
My question is how can this work (for the B observations) considering there appears to be no value for Tb? Is there another way it is being computed?
Here is my results from one night, untransformed and transformed respectively for T CrB:
B=11.486 and 11.502
V=10.177 and 10.151
I=7.525 and 7.531
I can send images if neccessary.