[Aavso-photometry] Normal Variation in Tranformation Coefficients?

[Greg Crawford]

I have been calculating transformation coefficients over a number of nights.
There is variation for each value. What range of variation is normal and what is
unacceptable?

A table of my results, across a number of nights (and sometimes on the same
night), shows:

B-V		 V		V-R		V-I
1.143		 0.047	1.124		1.224
1.182		 0.010	1.124		1.224
-		-0.095	1.023		0.952
-		 0.014	1.605		1.224
-		-0.065	1.021		0.882

Should I assume this variation is normal and just average results, or is the
variation suspect?

If they are suspect, what should I look for? As I understand my software, first
order extinction coefficients affect the calculation of T/Cs because they are
used to extrapolate to exoatmospheric magnitudes. So I assume extinction
measurements could be suspect (light clouds perhaps?) Is SNR another factor?
(That's why I left some B-V transformations above blank.)


Greg Crawford

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http://www.nelsonbay.com/~gc/observatory.htm