def observed_to_cirs(observed_coo, cirs_frame):
usrepr = observed_coo.represent_as(UnitSphericalRepresentation)
lon = usrepr.lon.to_value(u.radian)
lat = usrepr.lat.to_value(u.radian)
if isinstance(observed_coo, AltAz):
# the 'A' indicates zen/az inputs
coord_type = 'A'
lat = PIOVER2 - lat
else:
coord_type = 'H'
# first set up the astrometry context for ICRS<->CIRS at the observed_coo time
astrom = erfa_astrom.get().apio(observed_coo)
cirs_ra, cirs_dec = erfa.atoiq(coord_type, lon, lat, astrom) << u.radian
if isinstance(observed_coo.data, UnitSphericalRepresentation) or observed_coo.cartesian.x.unit == u.one:
distance = None
else:
distance = observed_coo.distance
cirs_at_aa_time = CIRS(ra=cirs_ra, dec=cirs_dec, distance=distance,
obstime=observed_coo.obstime,
location=observed_coo.location)
# this final transform may be a no-op if the obstimes and locations are the same
return cirs_at_aa_time.transform_to(cirs_frame)
def altaz_to_cirs(altaz_coo, cirs_frame):
usrepr = altaz_coo.represent_as(UnitSphericalRepresentation)
az = usrepr.lon.to_value(u.radian)
zen = PIOVER2 - usrepr.lat.to_value(u.radian)
# first set up the astrometry context for ICRS<->CIRS at the altaz_coo time
astrom = erfa_astrom.get().apio13(altaz_coo)
# the 'A' indicates zen/az inputs
cirs_ra, cirs_dec = erfa.atoiq('A', az, zen, astrom) * u.radian
if isinstance(altaz_coo.data, UnitSphericalRepresentation
) or altaz_coo.cartesian.x.unit == u.one:
cirs_at_aa_time = CIRS(ra=cirs_ra,
dec=cirs_dec,
distance=None,
obstime=altaz_coo.obstime)
else:
# treat the output of atoiq as an "astrometric" RA/DEC, so to get the
# actual RA/Dec from the observers vantage point, we have to reverse
# the vector operation of cirs_to_altaz (see there for more detail)
loccirs = altaz_coo.location.get_itrs(
altaz_coo.obstime).transform_to(cirs_frame)
astrometric_rep = SphericalRepresentation(lon=cirs_ra,
lat=cirs_dec,
distance=altaz_coo.distance)
newrepr = astrometric_rep + loccirs.cartesian
cirs_at_aa_time = CIRS(newrepr, obstime=altaz_coo.obstime)
# this final transform may be a no-op if the obstimes are the same
return cirs_at_aa_time.transform_to(cirs_frame)
def _erfa_check(ira, idec, astrom):
"""
This function does the same thing the astropy layer is supposed to do, but
all in erfa
"""
cra, cdec = erfa.atciq(ira, idec, 0, 0, 0, 0, astrom)
az, zen, ha, odec, ora = erfa.atioq(cra, cdec, astrom)
alt = np.pi / 2 - zen
cra2, cdec2 = erfa.atoiq('A', az, zen, astrom)
ira2, idec2 = erfa.aticq(cra2, cdec2, astrom)
dct = locals()
del dct['astrom']
return dct
def altaz_to_cirs(altaz_coo, cirs_frame):
usrepr = altaz_coo.represent_as(UnitSphericalRepresentation)
az = usrepr.lon.to_value(u.radian)
zen = PIOVER2 - usrepr.lat.to_value(u.radian)
lon, lat, height = altaz_coo.location.to_geodetic('WGS84')
xp, yp = get_polar_motion(altaz_coo.obstime)
# first set up the astrometry context for ICRS<->CIRS at the altaz_coo time
jd1, jd2 = get_jd12(altaz_coo.obstime, 'utc')
astrom = erfa.apio13(
jd1,
jd2,
get_dut1utc(altaz_coo.obstime),
lon.to_value(u.radian),
lat.to_value(u.radian),
height.to_value(u.m),
xp,
yp, # polar motion
# all below are already in correct units because they are QuantityFrameAttribues
altaz_coo.pressure.value,
altaz_coo.temperature.value,
altaz_coo.relative_humidity.value,
altaz_coo.obswl.value)
# the 'A' indicates zen/az inputs
cirs_ra, cirs_dec = erfa.atoiq('A', az, zen, astrom) * u.radian
if isinstance(altaz_coo.data, UnitSphericalRepresentation
) or altaz_coo.cartesian.x.unit == u.one:
cirs_at_aa_time = CIRS(ra=cirs_ra,
dec=cirs_dec,
distance=None,
obstime=altaz_coo.obstime)
else:
# treat the output of atoiq as an "astrometric" RA/DEC, so to get the
# actual RA/Dec from the observers vantage point, we have to reverse
# the vector operation of cirs_to_altaz (see there for more detail)
loccirs = altaz_coo.location.get_itrs(
altaz_coo.obstime).transform_to(cirs_frame)
astrometric_rep = SphericalRepresentation(lon=cirs_ra,
lat=cirs_dec,
distance=altaz_coo.distance)
newrepr = astrometric_rep + loccirs.cartesian
cirs_at_aa_time = CIRS(newrepr, obstime=altaz_coo.obstime)
# this final transform may be a no-op if the obstimes are the same
return cirs_at_aa_time.transform_to(cirs_frame)
def observed_to_icrs(observed_coo, icrs_frame):
# if the data are UnitSphericalRepresentation, we can skip the distance calculations
is_unitspherical = (isinstance(observed_coo.data,
UnitSphericalRepresentation)
or observed_coo.cartesian.x.unit == u.one)
usrepr = observed_coo.represent_as(UnitSphericalRepresentation)
lon = usrepr.lon.to_value(u.radian)
lat = usrepr.lat.to_value(u.radian)
if isinstance(observed_coo, AltAz):
# the 'A' indicates zen/az inputs
coord_type = 'A'
lat = PIOVER2 - lat
else:
coord_type = 'H'
# first set up the astrometry context for ICRS<->CIRS at the observed_coo time
astrom = erfa_astrom.get().apco(observed_coo)
# Topocentric CIRS
cirs_ra, cirs_dec = erfa.atoiq(coord_type, lon, lat, astrom) << u.radian
if is_unitspherical:
srepr = SphericalRepresentation(cirs_ra, cirs_dec, 1, copy=False)
else:
srepr = SphericalRepresentation(lon=cirs_ra,
lat=cirs_dec,
distance=observed_coo.distance,
copy=False)
# BCRS (Astrometric) direction to source
bcrs_ra, bcrs_dec = aticq(srepr, astrom) << u.radian
# Correct for parallax to get ICRS representation
if is_unitspherical:
icrs_srepr = UnitSphericalRepresentation(bcrs_ra, bcrs_dec, copy=False)
else:
icrs_srepr = SphericalRepresentation(lon=bcrs_ra,
lat=bcrs_dec,
distance=observed_coo.distance,
copy=False)
observer_icrs = CartesianRepresentation(astrom['eb'],
unit=u.au,
xyz_axis=-1,
copy=False)
newrepr = icrs_srepr.to_cartesian() + observer_icrs
icrs_srepr = newrepr.represent_as(SphericalRepresentation)
return icrs_frame.realize_frame(icrs_srepr)
def altaz_to_cirs(altaz_coo, cirs_frame):
usrepr = altaz_coo.represent_as(UnitSphericalRepresentation)
az = usrepr.lon.to_value(u.radian)
zen = PIOVER2 - usrepr.lat.to_value(u.radian)
# first set up the astrometry context for ICRS<->CIRS at the altaz_coo time
astrom = erfa_astrom.get().apio(altaz_coo)
# the 'A' indicates zen/az inputs
cirs_ra, cirs_dec = erfa.atoiq('A', az, zen, astrom) << u.radian
if isinstance(altaz_coo.data, UnitSphericalRepresentation
) or altaz_coo.cartesian.x.unit == u.one:
distance = None
else:
distance = altaz_coo.distance
cirs_at_aa_time = CIRS(ra=cirs_ra,
dec=cirs_dec,
distance=distance,
obstime=altaz_coo.obstime,
location=altaz_coo.location)
# this final transform may be a no-op if the obstimes and locations are the same
return cirs_at_aa_time.transform_to(cirs_frame)
