[AstroPy] Cross-Identification of stars in a collection of images

Erik Tollerud erik.tollerud@gmail....
Fri Mar 16 16:42:34 CDT 2012

Another useful resource that's actually build into scipy is the kdtree
module (scipy.spatial.kdtree).  It's not astronomy specific, but it's
an efficient way to do nearest-neighbor searches in arbitrary
coordinate spaces.  So you can e.g. feed in the ra/dec of objects from
the first image, and then use that to find nearest-neighbor (or nth
nearest neighbor) of the second image.  This is generally the way I do
coordinate matching, because it's one of the most efficient spatial
search algorithms out there. (Note that there's also a Cython version
in scipy.spatial.ckdtree... it has the exact same interface, but it's
compiled, so it's something like 10-100x faster, and possibly more

It doesn't do any kind of transformations though - you'd have to
figure that out based on the matches, I suppose.

On Wed, Mar 14, 2012 at 7:13 AM, Joe Philip Ninan <indiajoe@gmail.com> wrote:
> Hi,
> Is there any python function to cross-identify the stars between different
> frames and calculate the coefficients of coordinate transformation
> equations?
> If not, i am planning to implement it by first running daofind using pyraf
> and then trying to match triangles; starting from brightest stars.
> Is there any better/easier way to do this?
> Thanking you,
> Joe
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Erik Tollerud

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