[Aavso-photometry] V filter only - transforms possible?

[Tom Krajci]

I have a CCD/scope rig with only a V filter screwed into the CCD 
nosepiece.  No filter wheel, no other filters.

Here's the $64 question.  Is it possible to determine transformation 
coefficients for this setup with only a V filter?

If I do differential photometry of a Henden calibrated field (V 
magnitudes and color indices are known for the comps, *and* the target), 
can I transform to V magnitudes?

What if I take images of ye-olde standard field, M67, and compare my 
instrumental magnitudes with the catalog magnitudes?  What sort of 
correlation/transformation coefficient will that give me?  (If it's not 
a true transformation coefficient, then what is it called - a pseudo 
transform?)

(I know that if I use this V-filter-only rig on uncalibrated comps and 
targets, i.e. V mags and color indices are unknown,...then there is no 
way I can transform.  Therefore I'm looking for 'easy' target fields 
that I can work to higher precision...hopefully with a proper transform 
to V magnitudes.)

I'm just trying to get the most out of this V-filter-only system.  (And 
if I can't transform to V with this setup...how close can I get?  How do 
I report the magnitudes?...as untransformed?)  (And if I can't transform 
to V with this setup...what do I need to acquire?...a B or R filter?)

Thanks in advance.

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Tom Krajci
Cloudcroft, New Mexico
http://picasaweb.google.com/tom.krajci

Center for Backyard Astrophysics (CBA)
http://cbastro.org/ CBA New Mexico

American Association of Variable Star
Observers (AAVSO): KTC http://www.aavso.org/
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