Re: V image fainter than I

[Andrew Bennett <andrew.bennett@ns.sympatico.ca>]

On Fri, 18 Mar 2005 18:27:40 -0600 (CST), droege@snapmail.us wrote:

>...
>We could as Michael suggests assign some average (V-I).  I think this
>would be a little smaller than the 3-4 Michael suggests, but the result is
>still probably garbage.

Garbage? Are you sure?
How big is the effect anyway? I thought it was O(0.01 mags) 
for d(V-I) O(1). Is it really much bigget than this? I will admit
that my Ensemble programs have on occasion come up
with much larger coefficients but I assumed this was my
incompetence rather than something The Sky was doing!

I suspect some people would be perfectly happy with
unmatched I data so long as it was flagged as such and
so long as people were aware that the magnitudes
were uncorrected for colour or were corrected for
some assumed typical colour.

It would in any case be nice if the data base contained
somewhere the coefficients used to correct each image,
if only for those of us who trust nobody and would like to
go back and do it again from scratch ...
If only to make it possible for me to compare my PSF-fitting
program with data base pipeline results.

Andrew Bennett, Avondale Vineyard, NS, Canada