Re: Data reduction methodology for V-I colors

[Michael Koppelman <lolife@bitstream.net>]

Well I think a normal photometrist would take alternating fields of 
program stars and standards throughout the night and would in general 
create one transform for the whole night. If you have non-photometric 
conditions, you may need to divide the night into segments or 
something.

The good side of doing this is that we only use calibration stars of 
high quality i.e. use the best 50 stars from the night (e.g. Landolt 
and similar) instead of 50 stars from every frame of dubious quality.

I'm sure this is not a novel thought and it probably has complexities. 
I supposed I could get one or two nights of raw data from Tom and give 
it a try.

Cheers,
Michael

On Aug 31, 2004, at 1:33 PM, Creager, Robert S wrote:

> I'll show my ignorance here.  Seems like you can only use one zero 
> point
> across the entire night if you have no changing conditions across the 
> entire
> night (clouds, seeing?).  And, you would have to be careful to only 
> take
> pictures during astronomical twilight.  And, hope you live in an 
> evenly dark
> location (no nearby city/town).  Don't all these factors add up to a
> different zero point for every frame?