[Aavso-photometry] B-V from V-I

[Arne Henden]

James Bedient wrote:
> So the question I have: Is assuming dwarf stars and calculating U or Rc or I
> like that an acceptable way to operate for routine, patrol-type photometry?
> 
> For example, I was working through some faint CVs last night, and I stuck to B
> and V since I had V magnitude comps and B-V colors.  I could easily have run the
> gamut through UBVRcI, but didn't, since I lacked a sequence.
> 
> OK, I know, I could bite the bullet and shoot standard fields, but that
> resembles... work.  :-)
> You all know how I hate that.
> 
Yes, this is an acceptable method of obtaining other bandpasses.
You can also combine 2MASS information to give even better results.
However, to remove the giant/dwarf/extinction ambiguities, the
usual method is ensemble photometry, using as many comparison stars
as possible to smooth out the single-star transformation errors.
You should also post what comp stars you used and the values you
used for them so that someone can correct your results later when
improved measures are available.
Arne