Re: [Phys-l] Galaxies and clustering in astronomy

[alex brown <aesbrown77@yahoo.co.uk>]

Thank you Brian and John, 

I had looked at mathworks site, but not found this one.  I think this might be the answer, or tleast the easy answer for me to get going...A friend and I have written a hough programme already, but its was not v good at discerning circles.  Hence the question about clustering in hough space.  It likes to find circles where there are none, especially when circles are all translated along one direction.

Cheers
Alex   

--- On Sun, 15/5/11, brian whatcott <betwys1@sbcglobal.net> wrote:

From: brian whatcott <betwys1@sbcglobal.net>
Subject: Re: [Phys-l] Galaxies and clustering in astronomy
To: phys-l@carnot.physics.buffalo.edu
Date: Sunday, 15 May, 2011, 17:46

On 5/14/2011 2:27 AM, alex brown wrote:
> Hello All,
>
> I could not find anything about this in the archive so thought I'd ask here.
>
> I have a 3d array of points with each point having an "intensity."  I wish to group points into "galaxies," and wonder what algorithms are used in astronom?  Does anyon here have any experience in this? I am looking for something that would be quick and does not need to be 100% accurate. 
>
> As an aside the actual problem is......  circle recognition in an image from a fabry perot.  I have used hough transform and my 3d array is in "hough space." The array is sparse and thus I thought it is analogous to the problem of stars and assigning them to galaxies.  I don't want to reinvent the wheel so....
>
> Thanks for any suggestions
> Alex
>    
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Not sure how helpful it is: but a grey scale image can be processed in 
the Matlab application to
provide circle center locations and radii, see this:

<http://www.mathworks.com/matlabcentral/fileexchange/9168-detect-circles-with-various-radii-in-grayscale-image-via-hough-transform>

*http://tinyurl.com/42n7h3e*

Brian W

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