[AstroPy] Calculating alt/az or zenith angle/parallactic angle

[Francisco Gallardo lópez]

@Tim:

You may want to take a look at the Apsynsim <https://launchpad.net/apsynsim> .
It's a code in Python made by Ivan Martí (Chalmers Univ.). It's a R.
Astronomy interferometer simulator.

The code is available and includes a GUI. It uses the Hour Angle for the
calculations, so by looking at the "APSYNSIM.py" you may be able to
implement what you want ( def _changeCoordinates ?).

BTW: I read again my last email and realized that it should be HA = LST - ar[k]
 no the other way around.

@Erik: We were trying to calculate the EL curves (during a long time span)
for a large number of NEOs. We used JPL Spice to obtain the RA and DEC for
those instants. It was a matter of translating that to the observer local
Sky  (the idea was to generate a friendly web-based user interface). It was
quite slow and we thought it was due to this Issue:  https://github.com/
astropy/astropy/issues/3323

BR
Fran Gallardo

2017-01-30 10:33 GMT+01:00 Tim Cornwell <realtimcornwell at gmail.com>:

> Hi Erik,
>
> Thanks for the reply. I’m writing a reference library for SKA (part of the
> Science Data Processor consortium work), and as part of that I need to do
> simulations of observations with SKA. The configuration of an
> interferometric array is a function of hour angle and the absolute time is
> not relevant for most observations. So most of the simulations can be done
> in hour angle without having a choose a notional time. The reasons for this
> are that we can observe day or night. This isn’t always true but it mostly
> is. Some effects are purely dependent on Az, El (e.g. power patten of an
> array fixed to the ground or an alt-az antenna).
>
> I can do this in other packages (such as casa) but astropy is lightweight
> but capable so I’d rather use it if at all possible.
>
> Regards,
>
> Tim
>
> --
> Tim Cornwell
> Sent with Airmail
>
> On 30 January 2017 at 4:08:31 am, Erik Tollerud (erik.tollerud at gmail.com)
> wrote:
>
> Hi Francisco,
>
>
> > I think we discarded Skycoord due to the speed so we used PyEphem.
>
> Can you give a bit more on the specific use case that led you to this
> decision?  SkyCoord has a fair amount of space for optimization, so it
> would be useful to know what kinds of use cases are coming out as "slow" so
> we can try to make them better.
>
>
> ---
> Erik T
>
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