def test_angle_ops():
sign, idmsf = erfa.a2af(6, -np.pi)
assert sign == b'-'
assert idmsf.item() == (180, 0, 0, 0)
sign, ihmsf = erfa.a2tf(6, np.pi)
assert sign == b'+'
assert ihmsf.item() == (12, 0, 0, 0)
rad = erfa.af2a('-', 180, 0, 0.0)
np.testing.assert_allclose(rad, -np.pi)
rad = erfa.tf2a('+', 12, 0, 0.0)
np.testing.assert_allclose(rad, np.pi)
rad = erfa.anp(3. * np.pi)
np.testing.assert_allclose(rad, np.pi)
rad = erfa.anpm(3. * np.pi)
np.testing.assert_allclose(rad, -np.pi)
sign, ihmsf = erfa.d2tf(1, -1.5)
assert sign == b'-'
assert ihmsf.item() == (36, 0, 0, 0)
days = erfa.tf2d('+', 3, 0, 0.0)
np.testing.assert_allclose(days, 0.125)
def apio(frame_or_coord):
'''
Slightly modified equivalent of ``erfa.apio``, used in conversions AltAz <-> CIRS.
Since we use a topocentric CIRS frame, we have dropped the steps needed to calculate
diurnal aberration.
Parameters
----------
frame_or_coord : ``astropy.coordinates.BaseCoordinateFrame`` or ``astropy.coordinates.SkyCoord``
Frame or coordinate instance in the corresponding frame
for which to calculate the calculate the astrom values.
For this function, an AltAz frame is expected.
'''
# Calculate erfa.apio input parameters.
# TIO locator s'
sp = erfa.sp00(*get_jd12(frame_or_coord.obstime, 'tt'))
# Earth rotation angle.
theta = erfa.era00(*get_jd12(frame_or_coord.obstime, 'ut1'))
# Longitude and latitude in radians.
lon, lat, height = frame_or_coord.location.to_geodetic('WGS84')
elong = lon.to_value(u.radian)
phi = lat.to_value(u.radian)
# Polar motion, rotated onto local meridian
xp, yp = get_polar_motion(frame_or_coord.obstime)
# we need an empty astrom structure before we fill in the required sections
astrom = np.zeros(frame_or_coord.obstime.shape,
dtype=erfa.dt_eraASTROM)
# Form the rotation matrix, CIRS to apparent [HA,Dec].
r = (rotation_matrix(elong, 'z', unit=u.radian) @ rotation_matrix(
-yp, 'x', unit=u.radian) @ rotation_matrix(-xp, 'y', unit=u.radian)
@ rotation_matrix(theta + sp, 'z', unit=u.radian))
# Solve for local Earth rotation angle.
a = r[..., 0, 0]
b = r[..., 0, 1]
eral = np.arctan2(b, a)
astrom['eral'] = eral
# Solve for polar motion [X,Y] with respect to local meridian.
c = r[..., 0, 2]
astrom['xpl'] = np.arctan2(c, np.sqrt(a * a + b * b))
a = r[..., 1, 2]
b = r[..., 2, 2]
astrom['ypl'] = -np.arctan2(a, b)
# Adjusted longitude.
astrom['along'] = erfa.anpm(eral - theta)
# Functions of latitude.
astrom['sphi'] = np.sin(phi)
astrom['cphi'] = np.cos(phi)
# Omit two steps that are zero for a geocentric observer:
# Observer's geocentric position and velocity (m, m/s, CIRS).
# Magnitude of diurnal aberration vector.
# Refraction constants.
astrom['refa'], astrom['refb'] = erfa.refco(
frame_or_coord.pressure.to_value(u.hPa),
frame_or_coord.temperature.to_value(u.deg_C),
frame_or_coord.relative_humidity.value,
frame_or_coord.obswl.to_value(u.micron))
return astrom