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[vsnet-chat 1725] Re: BVRI Photometry
- Date: Mon, 29 Mar 1999 13:55:40 -0800 (PST)
- To: vsnet-chat@kusastro.kyoto-u.ac.jp
- From: Lew Cook <lcoo@yahoo.com>
- Subject: [vsnet-chat 1725] Re: BVRI Photometry
- Sender: owner-vsnet-chat@kusastro.kyoto-u.ac.jp
Stan asked about flat fielding different filters -
Here's an experiment you can do to see just how
important it is to flat field with each filter.
Take a flat frame through each filter, B, V, R and I.
Use the I flat and flat field each of the other 3 flats
using the I flat as your flat frame. The final frame
will show the relative variation over the chip in each
color relative to the I filter.
This will be a relative sensitivity map of the CCD in
each color. If you find there is no detectable
variation (unlikely) from one to the next, then perhaps
doing a flat in each color isn't warranted, but (more
likely) you will find variations and a systematic trend
across the chip. At any rate you will know a little
more about your chip.
===
Regards, Lew
- Visit http://home.pacbell.net/cookl
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