[AstroPy] Problem running pywcs example

Michael Droettboom mdroe at stsci.edu
Thu Aug 19 10:11:20 EDT 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.


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

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