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Re: automated PSF [message #70350]

Fri, 02 April 2010 11:30

wlandsman
Messages: 743
Registered: June 2000

Senior Member

>
> The problem with GETPSF is that it requires a list of stars from FIND;
> however, find requires that you feed it a FWHM for sources in the
> image, for which you would want to use the FWHM of the PSF, right? If
> not, then I'm confused.

For *finding* sources on an image you don't need to know the FWHM very
accurately. FIND will look for locally connected regions of
enhanced intensity that are roughly the size of your FWHM -- it will
throw out much narrower objects (e.g. cosmic rays) or much larger
objects (e.g. due to detector sensitivity variations). It is
probably good enough to simply look at your stars to see how many
pixels wide they are, though you could do a 2d Gaussian fit if you
wanted.

If you want to get accurate photometry in regions where star profiles
overlap, *then* you need to know the PSF much more accurately. --
Wayne

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[Message index]

		Re: automated PSF By: wlandsman on Fri, 02 April 2010 11:30
		Re: automated PSF By: Gray on Fri, 02 April 2010 10:44
		Re: automated PSF By: Jeremy Bailin on Fri, 02 April 2010 06:52

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