[AstroPy] Calculating alt/az or zenith angle/parallactic angle
Tim Cornwell
realtimcornwell at gmail.com
Fri Jan 27 05:56:42 EST 2017
Hi Tim,
I can see how that works bit what I want is to be able to calculate from the local hour angle i.e. a relative time (LST-RA) instead of starting with an absolute time. For context, I’m writing some simulation code and don’t need to work with absolute time. From what I see, it’s not possible in astropy to start with hour angle instead of some form of absolute time. I can work around this but it seems to be a hole in either the package or more likely in the documentation.
Thanks,
Tim
--
Tim Cornwell
Sent with Airmail
On 27 January 2017 at 10:51:42 am, Tim Staley (tim.staley at physics.ox.ac.uk) wrote:
Hi Tim,
you want something like the following:
from astropy.coordinates import SkyCoord, AltAz, EarthLocation
from astropy.time import Time
import astropy.units as u
obs_time = Time('2017-01-01T18:00')
sky_posn = SkyCoord(0 * u.deg, 30 * u.deg)
earth_location = EarthLocation.from_geodetic(0*u.deg, 35*u.deg)
altaz = sky_posn.transform_to(
AltAz(obstime=obs_time,
location=earth_location))
print(altaz.alt.deg, altaz.az.deg)
Cheers,
Tim
On 27/01/17 10:34, Tim Cornwell wrote:
> Hi
>
> I am given an hour angle and wish to calculate alt/az or zenith
> angle/parallactic angle for a given SkyCoord and Location. After
> reading the documentation and many tries, I cannot see how to do this
> with the current Astropy Time/Angle classes. It is possible?
>
> Thanks,
> Tim
>
> --
> Tim Cornwell
> Sent with Airmail
>
>
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