def toicrs(frame, ra, dec, equinox=2000.0, ut_datetime=None):
# Utility function. Converts and RA and Dec in the specified reference frame
# and equinox at ut_datetime into ICRS. This is used by the ra and dec descriptors.
# Assume equinox is julian calendar
equinox = 'J{}'.format(equinox)
# astropy doesn't understand APPT coordinates. However, it does understand
# CIRS coordinates, and we can convert from APPT to CIRS by adding the
# equation of origins to the RA. We can get that using ERFA.
# To proceed with this, we first let astopy construct the CIRS frame, so
# that we can extract the obstime object from that to pass to erfa.
appt_frame = (frame == 'APPT')
if frame == 'APPT':
frame = 'cirs'
if frame == 'FK5':
frame = 'fk5'
# Try this with the passed frame but, if it doesn't work, convert to "cirs"
# If that doesn't work, then raise an error
try:
coords = coordinates.SkyCoord(ra=ra * units.degree,
dec=dec * units.degree,
frame=frame,
equinox=equinox,
obstime=ut_datetime)
except ValueError:
frame = 'cirs'
coords = coordinates.SkyCoord(ra=ra * units.degree,
dec=dec * units.degree,
frame=frame,
equinox=equinox,
obstime=ut_datetime)
if appt_frame:
# Call ERFA.apci13 to get the Equation of Origin (EO).
# We just discard the astrom context return
astrom, eo = _erfa.apci13(coords.obstime.jd1, coords.obstime.jd2)
astrom = None
# eo comes back as a single element array in radians
eo = float(eo)
eo = eo * units.radian
# re-create the coords frame object with the corrected ra
coords = coordinates.SkyCoord(ra=coords.ra + eo,
dec=coords.dec,
frame=coords.frame.name,
equinox=coords.equinox,
obstime=coords.obstime)
# Now we can just convert to ICRS...
icrs = coords.icrs
# And return values in degrees
return (icrs.ra.degree, icrs.dec.degree)
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))
def toicrs(frame, ra, dec, equinox=2000.0, ut_datetime=None):
# Utility function. Converts and RA and Dec in the specified reference frame
# and equinox at ut_datetime into ICRS. This is used by the ra and dec descriptors.
# Assume equinox is julian calendar
equinox = 'J{}'.format(equinox)
# astropy doesn't understand APPT coordinates. However, it does understand
# CIRS coordinates, and we can convert from APPT to CIRS by adding the
# equation of origins to the RA. We can get that using ERFA.
# To proceed with this, we first let astopy construct the CIRS frame, so
# that we can extract the obstime object from that to pass to erfa.
appt_frame = (frame == 'APPT')
if frame == 'APPT':
frame = 'cirs'
if frame == 'FK5':
frame = 'fk5'
# Try this with the passed frame but, if it doesn't work, convert to "cirs"
# If that doesn't work, then raise an error
try:
coords = coordinates.SkyCoord(ra=ra*units.degree, dec=dec*units.degree,
frame=frame, equinox=equinox, obstime=ut_datetime)
except ValueError:
frame = 'cirs'
coords = coordinates.SkyCoord(ra=ra*units.degree, dec=dec*units.degree,
frame=frame, equinox=equinox, obstime=ut_datetime)
if appt_frame:
# Call ERFA.apci13 to get the Equation of Origin (EO).
# We just discard the astrom context return
astrom, eo = _erfa.apci13(coords.obstime.jd1, coords.obstime.jd2)
astrom = None
# eo comes back as a single element array in radians
eo = float(eo)
eo = eo * units.radian
# re-create the coords frame object with the corrected ra
coords = coordinates.SkyCoord(ra=coords.ra+eo, dec=coords.dec,
frame=coords.frame.name, equinox=coords.equinox,
obstime=coords.obstime)
# Now we can just convert to ICRS...
icrs = coords.icrs
# And return values in degrees
return (icrs.ra.degree, icrs.dec.degree)
def test_structs():
"""
Checks producing and consuming of ERFA c structs
"""
am, eo = erfa.apci13(2456165.5, [0.401182685, 1])
assert am.shape == (2, )
assert am.dtype == erfa.dt_eraASTROM
assert eo.shape == (2, )
# a few spotchecks from test_erfa.c
np.testing.assert_allclose(am[0]['pmt'], 12.65133794027378508)
np.testing.assert_allclose(am[0]['v'], [0.4289638897157027528e-4,
0.8115034002544663526e-4,
0.3517555122593144633e-4])
ri, di = erfa.atciqz(2.71, 0.174, am[0])
np.testing.assert_allclose(ri, 2.709994899247599271)
np.testing.assert_allclose(di, 0.1728740720983623469)