| Re: automated PSF [message #70350] |
Fri, 02 April 2010 11:30 |
wlandsman
Messages: 743
Registered: June 2000
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Senior Member |
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>
> 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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| Re: automated PSF [message #70351 is a reply to message #70350] |
Fri, 02 April 2010 10:44  |
Gray
Messages: 253
Registered: February 2010
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Senior Member |
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On Apr 2, 9:52 am, Jeremy Bailin <astroco...@gmail.com> wrote:
> On Apr 1, 10:09 pm, Gray <grayliketheco...@gmail.com> wrote:
>
>> Hi all,
>
>> Anyone have any ideas on how to automate finding the PSF of an image?
>> There are other applications out there where I could do it by hand (so
>> to speak), but I have a lot of images to process...
>
>> --Gray
>
> I'd try getpsf from the IDL astronomy user's library.
>
> -Jeremy.
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.
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| Re: automated PSF [message #70354 is a reply to message #70351] |
Fri, 02 April 2010 06:52 |
Jeremy Bailin
Messages: 618
Registered: April 2008
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Senior Member |
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On Apr 1, 10:09 pm, Gray <grayliketheco...@gmail.com> wrote:
> Hi all,
>
> Anyone have any ideas on how to automate finding the PSF of an image?
> There are other applications out there where I could do it by hand (so
> to speak), but I have a lot of images to process...
>
> --Gray
I'd try getpsf from the IDL astronomy user's library.
-Jeremy.
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