[AstroPy] RA-Dec to Alt-Az using Astropy 1.0

[Christoph Deil]

> On 11 Mar 2015, at 09:47, Akshat Singhal <akshat.singhal014 at gmail.com> wrote:
> 
> Hi all,
> 
> For some of my calculation I want to convert RA-Dec coordinates of a star to Alt-Az coordinates (for given location and time),
> make some other computations and then convert Alt-Az back to RA-dec.
> First conversion is easy, I am not able to figure out how to convert Alt-Az to RA-Dec in Astropy 1.0
> Any insight to this will be a lot helpful
> 
> Thanks and regards
> Akshat Singhal
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Hi Akshat,

to transform an from Alt-Az to Ra-Dec, you should create a SkyCoord with an AltAz frame and then call it’s `transform_to(‘icrs')` method or access it’s `.icrs` attribute.

There’s an example here in the Astropy tests:
https://github.com/astropy/astropy/blob/master/astropy/coordinates/tests/accuracy/test_altaz_icrs.py#L81 <https://github.com/astropy/astropy/blob/master/astropy/coordinates/tests/accuracy/test_altaz_icrs.py#L81>

I think it would be nice to add an example involving AltAz to the docs here:
http://astropy.readthedocs.org/en/latest/coordinates/transforming.html <http://astropy.readthedocs.org/en/latest/coordinates/transforming.html>

Christoph
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