From: Robert A. Knop Jr. (robert.a.knop@vanderbilt.edu)
Date: Sat Nov 02 2002 - 14:58:05 PST
On Sat, Nov 02, 2002 at 02:50:27PM -0800, Greg Aldering wrote:
> The summary is that if we coadd everything, the effective depths relative
> to 50 minute exposure with 0.8" seeing are 0.75, 0.79, 0.82, 0.71 and
> 0.92 in fields 1-5, respectively. If we only sum images with FWHM < 0.9"
> then the relative effective depths are 0.61, 0.69, 0.64, 0.47 and
> 0.75, respectively.
This is useful information. It looks like, in general, with the images
we have it doesn't *hurt* to add more worse seeing images. As such, the
first sums we should do should be including *all* the news, and try the
"better seeing" subset later (time permitting).
It does surprise me a bit that it doesn't hurt to add worse seeing
images-- although it's always incremental, there's never a real terrible
jump in seeing.
Note that the way you describe the method is a good model of what should
really happen when the code decides what aperture to use in searching
and photometry, so the results should have a good bearing on reality.
(Another wrinkle, of course, is cloud transparency. Adding images with
poor transparency adds noise out of proportion to the signal they
contribute.)
-Rob
-- --Prof. Robert Knop Department of Physics & Astronomy, Vanderbilt University robert.a.knop@vanderbilt.edu
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