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Re: change pixel scale [message #80331 is a reply to message #80321]

Sun, 27 May 2012 08:03

Russell Ryan
Messages: 122
Registered: May 2012

Senior Member

On May 26, 7:46 am, spasoklampa...@yahoo.com wrote:
> Hi
>
> I have some fits files (astronomy images) that have a different
> pixel scale. How is it possible to bring them on the same pixel scale?
> The given routine of degrade is not suitable, since it degrades the
> image resolution by a factor of two, which is not my case.
>
> Thanks a lot.

So...

There are several ways to skin this cat, and they depend on how
careful you want to be. Before we get into those ways, you need to
answer a few things about your images...

(1) Do they both have WCS in the headers that you trust?
(2) Are they astrometrically aligned already, and you just want to re-
pixelate?

If the answer to (1) is "no," then we need to fix that first.
Hopefully, you know *roughly* where your field is and can just grab a
bunch of stars either from the DSS or SDSS to get the precise WCS
mapped out. If not, then you need to go outside of IDL get the job
done.

Then you can use hastrom.pro (in the IDL astro library) to register
the two images. This does only a bilinear (I think?) interpolation
--- which may not be good enough for you. If you have a weight map
(or error image), then you need to process that as well --- but
remember you'll need to work with variances!!

If you don't like bilinear, then the only way I know how to do this is
to go outside of IDL and use SCAMP and SWarp to get the job done.

Good luck!
Russell

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[Message index]

		Re: change pixel scale By: spasoklampanas on Mon, 28 May 2012 09:17
		Re: change pixel scale By: Russell Ryan on Sun, 27 May 2012 08:03
		Re: change pixel scale By: spasoklampanas on Sat, 26 May 2012 08:56
		Re: change pixel scale By: wlandsman on Sat, 26 May 2012 08:28
		Re: change pixel scale By: spasoklampanas on Sat, 26 May 2012 07:34
		Re: change pixel scale By: wlandsman on Sat, 26 May 2012 07:01

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