comp.lang.idl-pvwave archive: archive

Home » Public Forums » archive » Least square fitting

Show: Today's Messages :: Show Polls :: Message Navigator
E-mail to friend

Re: Least square fitting [message #60467 is a reply to message #60326]

Wed, 21 May 2008 00:47

Bringfried Stecklum is currently offline

Bringfried Stecklum
Messages: 75
Registered: January 1996

Member

Marshall Perrin wrote:
> MichaelT <michael.theusner@googlemail.com> wrote:
>> Hi all,
>>
>> I have a problem with a rather complicated function depending on four
>> parameters which I try to find using least square fitting and I don't
>> know exactly how to do it.
>>
>> The basic problem is the following:
>> I have an astronomical image of a star field and try to relate the sky
>> coordinates (right ascension, declination) of the stars to the pixel
>> coordinates (x, y).
>
> So if you truly wish to know how to properly solve this particular
> mathematical problem, I will leave that to other wiser experts to
> answer.
>
> If, however, what you really want is just to know the astrometric
> solution for your data, you may be interested to know about
> Astrometry.net, a research project by David Hogg at NYU and
> collaborators which intends to solve this particular problem once and
> for all, for everyone. You feed their web service arbitrary
> astronomical images, and it hands back the astrometric solution. I've
> not tried it for images as wide-field as you have, but I suspect it
> will work just fine. See http://astrometry.net/ for more info.
>
> - Marshall
I agree with Marshall. Astrometry.net offers a good service and the
code works well if the FOV is not too small (i.e. there are enough
stars to match). However, it does not take (yet) advantage of the WCS
info provided by the FITS header. For your purpose the TERAPIX
procedures SCAMP and SWARP can be used. The former establishes
the astrometry (including field distortion) while the latter does the image
transformation, i.e. creates a non-distorted output mosaic. You might
want to have a look at the TERAPIX website for more information.

Regards,

Bringfried

Report message to a moderator

[Message index]

		Least square fitting By: MichaelT on Tue, 20 May 2008 02:41
		Re: Least square fitting By: MichaelT on Wed, 21 May 2008 01:45
		Re: Least square fitting By: Bringfried Stecklum on Wed, 21 May 2008 00:47
		Re: Least square fitting By: Marshall Perrin on Tue, 20 May 2008 14:48
		Re: Least square fitting By: MichaelT on Tue, 20 May 2008 11:44
		Re: Least square fitting By: wlandsman on Tue, 20 May 2008 10:28

Previous Topic:	interact with iimage from the command line?
Next Topic:	Re: problem in using function ll_to_utm.pro

-=] Back to Top [=-

[ Syndicate this forum (XML) ] [

] [

]

Current Time: Fri Oct 10 09:43:26 PDT 2025

Total time taken to generate the page: 0.63947 seconds