[AstroPy] [pywcs] Unit question

Perry Greenfield perry at stsci.edu
Tue Apr 5 08:04:45 EDT 2011

On Apr 5, 2011, at 6:18 AM, Ole Streicher wrote:

> Am 05.04.2011 09:33, schrieb Nico Nell:
>> This can be done easily with astLib (http://astlib.sourceforge.net/).
>> See function clipImageSectionWCS
>> (http://astlib.sourceforge.net/docs/astLib/astLib.astImages-module.html#clipImageSectionWCS 
>> ).
>> Here is an example that I used to make clips from big GALEX fits  
>> files
>> (http://casa.colorado.edu/~nell/cgit/cgit.cgi/pyscripts/tree/plotting/galex-clips.py 
>> )
>> Hopefully this makes things easier for you!
> Thank you, Nico.
> However, I started now using pywcs, and I would probably stick to that
> unless I cannot use the problem with it.
> I am still quite confused why there are parallel packages doing mainly
> the same thing: astLib and astrolib are quite for the same purpose,  
> and
> having both f.e. a wcslib wrapper. In my opinion, this parallel
> development seems to me quite unnecessary and delays cooperation since
> everyone historically uses his own preferred library. For different
> programming languages, I could understand this, but I dont see a real
> reason to have different pywcs modules.
> Are there any attempts to unify the different approaches for
> astro(python|lib)? What is the common opinion about the fragmentation
> problem?

Actually, I'd like to help such a unification. WCS seems like an  
obvious place to start (it's not the only case though).

Mind you, I'm not adverse to people trying different approaches early  
on to see what works best, but after some point consolidation is  
usually a good idea.

So perhaps this is a good starting point for doing so with WCS. I  
haven't studied the details of this particular instance that much, but  
it certainly makes sense that one should be able to easily generate a  
new  WCS for a subarray. If pywcs can't do that yet, we should add  
that capability.

To the maintainers of the other wcs packages, what capabilities do you  
think pywcs is missing? Is there some way of merging the missing  
capabilities? Or is there a disagreement on the proper object model or  
interfaces? This seems like a good time to start such a discussion.


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