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Re: CD5 Saturated Sources again
On Tue, 28 Dec 1999 17:13:18 -0600, Tom Droege <email@example.com> wrote:
*>If I understand you correctly, the +.22 "across the image" in RA (I send
*>them out with RA up/down so I assume that you have rotated the image) means
*>that the magnitude goes down by .22 mag as you go from the first scanned
*>pixel to the last.
*>Likewise, the image gets dimmer from the first scanned line to the last by
*>Do I have it right?
*>At 08:35 PM 12/24/99 GMT, you wrote:
*>>The trends removed were +0.22 +- 0.03 magnitudes across the image
*>>in RA and +0.11 magnitudes in DEC. These appear to be real and
*>>a "feature" of the CCD and/or electronics.
...or of the optics!
I believe these effects are either due to coma, or at least they
are obscured by coma. I have a thought experiment, maybe I will do it
as time permits but I will lay it out now. Some of the Mark IV CD #5 images
appear relatively free of "clouds" or irregular variations in background
when examined visually. But they have a "cross" pattern as a background
that is darker in the corners. I think THAT is coma spreading the
background out at the corners. Local measures of background throughout
the image - this is what a flat field does in part - may suggest the average
effects of coma AND might be informative about any loss of CCD efficiency
along the columns.
My simple programs (on the TASS section of my Web page) will allow me to do
this with not much fuss.
Herbert R. Johnson http://pluto.njcc.com/~hjohnson
firstname.lastname@example.org voice 609-771-1503, New Jersey USA
amateur astronomer and astro-tour guide
S-100 computer restoration, parts, manuals as "Dr. S-100"
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