[AstroPy] Summer scholar

Rene Breton superluminique@gmail....
Mon Aug 2 23:04:37 CDT 2010


Hi everyone,


Thanks for sharing your tips/library Stefano. Indeed a matching routine would be very nice to have so people should definitely aim to have something that makes use of several criteria such as distance and magnitude (in a more generic way). The Groth/Stetson algorithm seems very good but maybe yours is similar or can do better. Worse case, both can be put in under different names a little bit like the different root finding algorithms in scipy.optimize. You can never have enough algorithms to get around pathological problems.

Now, regarding Wolfgang's post, I very much agree with his ideas. I have to say that I've already implemented the "find" from "find.pro" in IDL's astrolib, which works really well in order to identify point sources. At the same time, I've modernized the program so that it takes advantage of numpy's array algebra, hence there are no slow "for loops". Maybe other algorithms could be worked out but this one certainly works well and it would be a shame to re-invent the wheel and have someone redo it. I think it should have been committed in the "pyastrolib" project that I was part of. If not, I'm very happy to add it here.

I'm also not very far from having a re-brewed "aper" function working, from "aper.pro" in IDL's astrolib but there are a couple of function dependencies that I haven't had try to code. So maybe the students could start from there in their coding.

Here are two ideas that I'd like to throw in for the student project, but they also apply in a more general way:
1. IDL's astrolib is a good start. The phot/daophot stuff from IDL's astrolib is generally pretty good, though it would gain to be modernized (and make use of array operations for instance). Since IDL and python are arguably similar, it would probably be not too difficult for someone with minimal experience to port some IDL code to python. Then one can optimize it.
2. Working on new photometry algorithms. Despite students may have limited programming background, they might be clever physicists. There are different algorithm using maximum entropy and such that can try to optimized the number of fitted sources. Among other interesting things would be algorithms/functions to derive photometric upper limits. This is what annoys me most and IDL's astrolib totally misses it. For PSF photometry, a routine that adds fake stars and tries to retrieve their flux in order to asses upper limits would be awesome. Something should also be done for aperture photometry.


Cheers,


Rene






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