[AstroPy] Problem running pywcs example

Michael Droettboom mdroe@stsci....
Thu Aug 19 09:11:20 CDT 2010


On 08/19/2010 09:23 AM, Michael Droettboom wrote:
> On 08/18/2010 03:56 PM, Peter Erwin wrote:
>> Hi Mike,
>>
>> Thanks for the quick reply!
>>
>> It looks like what happened is that *was* an earlier version of pywcs hiding
>> in /Users/erwin/lib/python [as opposed to
>> /Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6 ,
>> which is where pywcs 1.9 got installed].  Possibly it got installed as part of
>> an earlier installation of stsci_python ...
>>
>> Anyway, I nuked the earlier installation, and now pywcs seems to work.
>>
>>
>> Am I missing something, or does the documentation for pywcs mention anywhere what
>> "sky coordinates" actually means (i.e., allowed formats, types, order, etc.?).
>>    
>
> The order is described in the wcs_sky2pix docstring:
>
> """
>
> Either two or three arguments may be provided.
>
>         * 2 arguments: An /N/ x /naxis/ array of /x/- and
>           /y/-coordinates, and an /origin/.
>         * 3 arguments: 2 one-dimensional arrays of /x/ and /y/
>           coordinates, and an /origin/.
>
> """
>
> As for types, it may be any numeric type (and the underlying 
> calculations are performed in doubles).
And for additional clarification, I should add that the order (whether 
it's [dec, ra] or [ra, dec]) depends on the CTYPEia arguments in the 
FITS header.  You can determine that programmatically (if necessary) 
from the .lat, .lng, .lattype and .lngtype members.

Mike

-- 
Michael Droettboom
Science Software Branch
Space Telescope Science Institute
Baltimore, Maryland, USA

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