def test_hgc_self_observer():
# Test specifying observer='self' for HGC
obstime = Time('2001-01-01')
hgc = HeliographicCarrington(10*u.deg, 20*u.deg, 3*u.AU, observer='self', obstime=obstime)
# Transform to HGS (i.e., observer='self' in the source frame)
hgs = hgc.transform_to(HeliographicStonyhurst(obstime=obstime))
# Manually calculate the post-transformation longitude
lon = sun.L0(obstime,
light_travel_time_correction=False,
nearest_point=False,
aberration_correction=False)
lon += (hgc.radius - _RSUN) / speed_of_light * sidereal_rotation_rate
assert_quantity_allclose(Longitude(hgs.lon + lon), hgc.lon)
assert_quantity_allclose(hgs.lat, hgc.lat)
assert_quantity_allclose(hgs.radius, hgc.radius)
# Transform back to HGC (i.e., observer='self' in the destination frame)
hgc_loop = hgs.transform_to(hgc.replicate_without_data())
assert_quantity_allclose(hgc_loop.lon, hgc.lon)
assert_quantity_allclose(hgc_loop.lat, hgc.lat)
assert_quantity_allclose(hgc_loop.radius, hgc.radius)
def test_hgc_loopback_self_observer():
# Test the HGC loopback where only one end has observer='self'
obstime = Time('2001-01-01')
coord = HeliographicCarrington(10*u.deg, 20*u.deg, 3*u.AU, observer='self', obstime=obstime)
new_observer = HeliographicStonyhurst(40*u.deg, 50*u.deg, 6*u.AU)
new_frame = HeliographicCarrington(observer=new_observer, obstime=obstime)
new_coord = coord.transform_to(new_frame)
# Manually calculate the longitude shift due to the difference in Sun-observer distance
lon = (6*u.AU - 3*u.AU) / speed_of_light * sidereal_rotation_rate
assert_quantity_allclose(new_coord.lon, coord.lon + lon)
assert_quantity_allclose(new_coord.lat, coord.lat)
assert_quantity_allclose(new_coord.radius, coord.radius)