def test_setting_object_on_the_equator_is_90_minus_latitude(self):
"""
For a setting object on the equator, the parallactic angle
is 90 - lat
"""
lat = np.random.rand(10) * 180 - 90
pa = parallactic_angle(6, 0, lat)
assert np.allclose(pa, 90. - lat)
def test_specific_example_from_Ball_1908(self):
"""Test: Example from Ball (1908), p.92"""
ha = -3. # 3 hours east
de = 38 + 9/60. # decl 38d09m
lat = 53 + 23/60. # lat 53d23m
eta0 = - (48 + 41/60.) # result -48d41m
eta = parallactic_angle(ha, de, lat)
# should agree to within 1 arcmin
assert np.allclose(eta, eta0, atol=1/60.)
def test_parallactic_angle_positive_west_of_meridian(self):
assert parallactic_angle(1, 0, -24) > 0
def test_parallactic_angle_zero_on_meridian(self):
assert parallactic_angle(0, 0, 24) == 0
def test_parallactic_angle_negative_east_of_meridian(self):
assert parallactic_angle(-1, 0, -24) < 0