Module pymap3d.azelradec
Azimuth / elevation <==> Right ascension, declination
Source code
"""
Azimuth / elevation <==> Right ascension, declination
"""
from typing import Tuple
from datetime import datetime
from .vallado import azel2radec as vazel2radec, radec2azel as vradec2azel
from .timeconv import str2dt # astropy can't handle xarray times (yet)
try:
from astropy.time import Time
from astropy import units as u
from astropy.coordinates import Angle, SkyCoord, EarthLocation, AltAz, ICRS
except ImportError:
Time = None
__all__ = ["radec2azel", "azel2radec"]
def azel2radec(
az_deg: float, el_deg: float, lat_deg: float, lon_deg: float, time: datetime, usevallado: bool = False
) -> Tuple[float, float]:
"""
viewing angle (az, el) to sky coordinates (ra, dec)
Parameters
----------
az_deg : float
azimuth [degrees clockwize from North]
el_deg : float
elevation [degrees above horizon (neglecting aberration)]
lat_deg : float
observer latitude [-90, 90]
lon_deg : float
observer longitude [-180, 180] (degrees)
time : datetime.datetime or str
time of observation
usevallado : bool, optional
default use astropy. If true, use Vallado algorithm
Returns
-------
ra_deg : float
ecliptic right ascension (degress)
dec_deg : float
ecliptic declination (degrees)
"""
if usevallado or Time is None: # non-AstroPy method, less accurate
return vazel2radec(az_deg, el_deg, lat_deg, lon_deg, time)
obs = EarthLocation(lat=lat_deg * u.deg, lon=lon_deg * u.deg)
direc = AltAz(location=obs, obstime=Time(str2dt(time)), az=az_deg * u.deg, alt=el_deg * u.deg)
sky = SkyCoord(direc.transform_to(ICRS()))
return sky.ra.deg, sky.dec.deg
def radec2azel(
ra_deg: float, dec_deg: float, lat_deg: float, lon_deg: float, time: datetime, usevallado: bool = False
) -> Tuple[float, float]:
"""
sky coordinates (ra, dec) to viewing angle (az, el)
Parameters
----------
ra_deg : float
ecliptic right ascension (degress)
dec_deg : float
ecliptic declination (degrees)
lat_deg : float
observer latitude [-90, 90]
lon_deg : float
observer longitude [-180, 180] (degrees)
time : datetime.datetime or str
time of observation
usevallado : bool, optional
default use astropy. If true, use Vallado algorithm
Returns
-------
az_deg : float
azimuth [degrees clockwize from North]
el_deg : float
elevation [degrees above horizon (neglecting aberration)]
"""
if usevallado or Time is None:
return vradec2azel(ra_deg, dec_deg, lat_deg, lon_deg, time)
obs = EarthLocation(lat=lat_deg * u.deg, lon=lon_deg * u.deg)
points = SkyCoord(Angle(ra_deg, unit=u.deg), Angle(dec_deg, unit=u.deg), equinox="J2000.0")
altaz = points.transform_to(AltAz(location=obs, obstime=Time(str2dt(time))))
return altaz.az.degree, altaz.alt.degreeFunctions
def azel2radec(az_deg, el_deg, lat_deg, lon_deg, time, usevallado=False)-
viewing angle (az, el) to sky coordinates (ra, dec)
Parameters
az_deg:float- azimuth [degrees clockwize from North]
el_deg:float- elevation [degrees above horizon (neglecting aberration)]
lat_deg:float- observer latitude [-90, 90]
lon_deg:float- observer longitude [-180, 180] (degrees)
time:datetime.datetimeorstr- time of observation
usevallado:bool, optional- default use astropy. If true, use Vallado algorithm
Returns
ra_deg:float- ecliptic right ascension (degress)
dec_deg:float- ecliptic declination (degrees)
Source code
def azel2radec( az_deg: float, el_deg: float, lat_deg: float, lon_deg: float, time: datetime, usevallado: bool = False ) -> Tuple[float, float]: """ viewing angle (az, el) to sky coordinates (ra, dec) Parameters ---------- az_deg : float azimuth [degrees clockwize from North] el_deg : float elevation [degrees above horizon (neglecting aberration)] lat_deg : float observer latitude [-90, 90] lon_deg : float observer longitude [-180, 180] (degrees) time : datetime.datetime or str time of observation usevallado : bool, optional default use astropy. If true, use Vallado algorithm Returns ------- ra_deg : float ecliptic right ascension (degress) dec_deg : float ecliptic declination (degrees) """ if usevallado or Time is None: # non-AstroPy method, less accurate return vazel2radec(az_deg, el_deg, lat_deg, lon_deg, time) obs = EarthLocation(lat=lat_deg * u.deg, lon=lon_deg * u.deg) direc = AltAz(location=obs, obstime=Time(str2dt(time)), az=az_deg * u.deg, alt=el_deg * u.deg) sky = SkyCoord(direc.transform_to(ICRS())) return sky.ra.deg, sky.dec.deg def radec2azel(ra_deg, dec_deg, lat_deg, lon_deg, time, usevallado=False)-
sky coordinates (ra, dec) to viewing angle (az, el)
Parameters
ra_deg:float- ecliptic right ascension (degress)
dec_deg:float- ecliptic declination (degrees)
lat_deg:float- observer latitude [-90, 90]
lon_deg:float- observer longitude [-180, 180] (degrees)
time:datetime.datetimeorstr- time of observation
usevallado:bool, optional- default use astropy. If true, use Vallado algorithm
Returns
az_deg:float- azimuth [degrees clockwize from North]
el_deg:float- elevation [degrees above horizon (neglecting aberration)]
Source code
def radec2azel( ra_deg: float, dec_deg: float, lat_deg: float, lon_deg: float, time: datetime, usevallado: bool = False ) -> Tuple[float, float]: """ sky coordinates (ra, dec) to viewing angle (az, el) Parameters ---------- ra_deg : float ecliptic right ascension (degress) dec_deg : float ecliptic declination (degrees) lat_deg : float observer latitude [-90, 90] lon_deg : float observer longitude [-180, 180] (degrees) time : datetime.datetime or str time of observation usevallado : bool, optional default use astropy. If true, use Vallado algorithm Returns ------- az_deg : float azimuth [degrees clockwize from North] el_deg : float elevation [degrees above horizon (neglecting aberration)] """ if usevallado or Time is None: return vradec2azel(ra_deg, dec_deg, lat_deg, lon_deg, time) obs = EarthLocation(lat=lat_deg * u.deg, lon=lon_deg * u.deg) points = SkyCoord(Angle(ra_deg, unit=u.deg), Angle(dec_deg, unit=u.deg), equinox="J2000.0") altaz = points.transform_to(AltAz(location=obs, obstime=Time(str2dt(time)))) return altaz.az.degree, altaz.alt.degree