[Aavso-photometry] Transform coefficients and two-filter measurements

[tom_krajci at tularosa.net]

> You don't care about B or V you care about B-V and it is simply either
> redder or bluer. B-V is a single quantity, in a sense.

B-V can be considered a single quantity, but it takes two different
measurements...in two different filter bands.

These two filter bands are independent of each other.  (In other words,
one filter bandpass may be rather blue compared to the catalog
values...and the other filter bandpass...can be anything from red to blue
of catalog values.)

I'm trying to get a deeper understanding, at a conceptual level, of what
is going on here with two independent measurements to arrive at one
quantity.

Is the deviation of instrumental b-v versus catalog B-V...always a
straight line?  Can there be considerable curvature?  How is it
governed/controlled/determined by the two measurements?

Tom Krajci