[AstroPy] Python Functions for Horizontal to Equatorial and vice versa?

Victoria G. Laidler laidler@stsci....
Thu Apr 22 09:32:10 CDT 2010

Hi all,

Johann Cohen-Tanugi wrote:
> hi Wayne,
> I am getting a bit lost in the reorganization of the sts software, and 
> several cross-references from sts to scipy seem broken.
> Anyway, there is https://www.stsci.edu/trac/ssb/astrolib
> and inside you have the package coords, which was claimed to be a large 
> port of the IDM astron library parts that deal with astronomical 
> coordinates. I am not sure what the status of this is. Anyone on this list?
I'm the primary developer of the Coords package. It's not in active 
development right now but what's there is stable. It doesn't presently 
provide transformation methods to and from altazimuth coordinates, but 
the Position.tpmstate() method does provide an "expert user" interface 
for the underlying TPM package, which does. You can see the API docs here:

I don't have the time right now to implement support for altaz 
coordinates, but if anyone else wants to do so we'll happily take a 
patch if it comes with tests.

Vicki Laidler

> On 04/21/2010 05:46 AM, Anne Archibald wrote:
>> On 19 April 2010 15:15, Wayne Watson<sierra_mtnview@sbcglobal.net>  wrote:
>>> I'm looking for two functions to do the coordinate transformations in
>>> the Subject.  Just those two. I don't need any others.
>> I think you will find that you need many other functions than just
>> horizontal to equatorial: the transformation depends on LST, for
>> example, which you will need to convert to or from GMT, and on
>> latitude/longitude; you'll probably want to convert various
>> coordinates between sexagesimal and radians or degrees; you may even
>> find galactic coordinates useful. Just go with something like a python
>> wrapper for SLALIB.
>> If you really want just those two functions, if it's really essential
>> to keep dependencies down at the cost of debugging pain, you can write
>> such a function fairly easily by converting to a 3D vector
>> representation and back.
>> Good luck,
>> Anne

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