def icrs_to_altaz(icrs_coo, altaz_frame):
# if the data are UnitSphericalRepresentation, we can skip the distance calculations
is_unitspherical = (isinstance(icrs_coo.data, UnitSphericalRepresentation)
or icrs_coo.cartesian.x.unit == u.one)
# first set up the astrometry context for ICRS<->AltAz
astrom = erfa_astrom.get().apco(altaz_frame)
# correct for parallax to find BCRS direction from observer (as in erfa.pmpx)
if is_unitspherical:
srepr = icrs_coo.spherical
else:
observer_icrs = CartesianRepresentation(astrom['eb'],
unit=u.au,
xyz_axis=-1,
copy=False)
srepr = (icrs_coo.cartesian -
observer_icrs).represent_as(SphericalRepresentation)
# convert to topocentric CIRS
cirs_ra, cirs_dec = atciqz(srepr, astrom)
# now perform AltAz conversion
az, zen, ha, odec, ora = erfa.atioq(cirs_ra, cirs_dec, astrom)
alt = PIOVER2 - zen
if is_unitspherical:
aa_srepr = UnitSphericalRepresentation(az << u.radian,
alt << u.radian,
copy=False)
else:
aa_srepr = SphericalRepresentation(az << u.radian,
alt << u.radian,
srepr.distance,
copy=False)
return altaz_frame.realize_frame(aa_srepr)
def test_atciqz_aticq(t, pos):
"""Check replacements against erfa versions for consistency."""
jd1, jd2 = get_jd12(t, 'tdb')
astrom, _ = erfa.apci13(jd1, jd2)
ra = pos.lon.to_value(u.rad)
dec = pos.lat.to_value(u.rad)
assert_allclose(erfa.atciqz(ra, dec, astrom), atciqz(pos, astrom))
assert_allclose(erfa.aticq(ra, dec, astrom), aticq(pos, astrom))
def test_atciqz_aticq(st):
"""Check replacements against erfa versions for consistency."""
t, pos = st
jd1, jd2 = get_jd12(t, 'tdb')
astrom, _ = erfa.apci13(jd1, jd2)
ra, dec = pos
ra = ra.value
dec = dec.value
assert_allclose(erfa.atciqz(ra, dec, astrom), atciqz(ra, dec, astrom))
assert_allclose(erfa.aticq(ra, dec, astrom), aticq(ra, dec, astrom))
def test_atciqz_aticq(st):
"""Check replacements against erfa versions for consistency."""
t, pos = st
jd1, jd2 = get_jd12(t, 'tdb')
astrom, _ = erfa.apci13(jd1, jd2)
ra, dec = pos
ra = ra.value
dec = dec.value
assert_allclose(erfa.atciqz(ra, dec, astrom), atciqz(ra, dec, astrom))
assert_allclose(erfa.aticq(ra, dec, astrom), aticq(ra, dec, astrom))