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| Pippo |
01/23/2009 11:58AM (Read 1794 times)
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Status: offline
Registered: 01/23/2009
Posts: 2
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Hi, I would want to know how I can eliminate the sky from a scientific image for photometrical analysis.ThanksPippo
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| jturner |
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01/23/2009 11:58AM
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Status: offline
Registered: 12/29/2005
Posts: 165
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I'm no expert, but photometric analysis routines typically calculate the background around the extraction aperture for you and subtract it off. They may even [i:4cff12df52]require[/i:4cff12df52] that your image contain the sky level for proper signal-to-noise optimization or whatever. Otherwise, if you have several images taken at slightly different pointings/offsets and your source is not too extended, you could combine the exposures with statistical rejection of the brightest pixels (eg. using imcombine) to remove the stars and just get sky, then subtract that from each image with imarith or imexpr.James.
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