def test_array(self):
# Do a simple test of transit_RA in an array. Use the fact that the RA
# advances predictably to predict the answers
from skyfield import earthlib
epoch = datetime(2000, 1, 1, 11, 58, 56)
# Create an observer at an arbitrary location
obs = ctime.Observer(118.3, 36.1)
# Calculate LST
t = ctime.unix_to_skyfield_time(ctime.datetime_to_unix(epoch))
gst = earthlib.sidereal_time(t)
lst = (360.0 * gst / 24.0 + obs.longitude) % 360.0
# Drift rate should be very close to 1 degree/4minutes.
# Fetch times calculated by ephem
delta_deg = np.arange(20)
delta_deg.shape = (5, 4)
lst = lst + delta_deg
# Calculate RA using transit_RA
unix_epoch = ctime.datetime_to_unix(epoch)
unix_times = unix_epoch + (delta_deg * 60 * 4 * ctime.SIDEREAL_S)
TRA = obs.transit_RA(unix_times)
# Compare
self.assertTrue(np.allclose(lst, TRA, atol=0.02, rtol=1e-10))
def test_array(self):
# Do a simple test of transit_RA in an array. Use the fact that the RA
# advances predictably to predict the answers
from skyfield import earthlib
epoch = datetime(2000, 1, 1, 11, 58, 56)
# Create an observer at an arbitrary location
obs = ctime.Observer(118.3, 36.1)
# Calculate LST
t = ctime.unix_to_skyfield_time(ctime.datetime_to_unix(epoch))
gst = earthlib.sidereal_time(t)
lst = (360.0 * gst / 24.0 + obs.longitude) % 360.0
# Drift rate should be very close to 1 degree/4minutes.
# Fetch times calculated by ephem
delta_deg = np.arange(20)
delta_deg.shape = (5, 4)
lst = lst + delta_deg
# Calculate RA using transit_RA
unix_epoch = ctime.datetime_to_unix(epoch)
unix_times = unix_epoch + (delta_deg * 60 * 4 * ctime.SIDEREAL_S)
TRA = obs.transit_RA(unix_times)
# Compare
self.assertTrue(np.allclose(lst, TRA, atol=0.02, rtol=1e-10))
def test_sidereal_time_with_nonzero_delta_t():
epsilon = 1e-13
st0 = c.sidereal_time(T0, 0.0, D0, False, True)
stA = c.sidereal_time(TA, 0.0, DA, False, True)
stB = c.sidereal_time(TB, 0.0, DB, False, True)
jd = JulianDate(ut1=[T0, TA, TB], delta_t=[D0, DA, DB])
v = earthlib.sidereal_time(jd)
eq(v, [st0, stA, stB], epsilon)
def test_sidereal_time_with_zero_delta_t():
epsilon = 1e-13
delta_t = 0.0
st0 = c.sidereal_time(T0, 0.0, delta_t, False, True)
stA = c.sidereal_time(TA, 0.0, delta_t, False, True)
stB = c.sidereal_time(TB, 0.0, delta_t, False, True)
jd = JulianDate(ut1=[T0, TA, TB], delta_t=delta_t)
v = earthlib.sidereal_time(jd)
eq(v, [st0, stA, stB], epsilon)
def test_epoch(self):
from skyfield import earthlib
# At the J2000 epoch, sidereal time and transit RA should be the same.
epoch = datetime(2000, 1, 1, 11, 58, 56)
# Create an observer at an arbitrary location
obs = ctime.Observer(118.3, 36.1)
# Calculate the transit_RA
unix_epoch = ctime.datetime_to_unix(epoch)
TRA = obs.transit_RA(unix_epoch)
# Calculate LST
t = ctime.unix_to_skyfield_time(unix_epoch)
gst = earthlib.sidereal_time(t)
lst = (360.0 * gst / 24.0 + obs.longitude) % 360.0
# Tolerance limited by stellar aberation
self.assertTrue(np.allclose(lst, TRA, atol=0.01, rtol=1e-10))
def test_epoch(self):
from skyfield import earthlib
# At the J2000 epoch, sidereal time and transit RA should be the same.
epoch = datetime(2000, 1, 1, 11, 58, 56)
# Create an observer at an arbitrary location
obs = ctime.Observer(118.3, 36.1)
# Calculate the transit_RA
unix_epoch = ctime.datetime_to_unix(epoch)
TRA = obs.transit_RA(unix_epoch)
# Calculate LST
t = ctime.unix_to_skyfield_time(unix_epoch)
gst = earthlib.sidereal_time(t)
lst = (360.0 * gst / 24.0 + obs.longitude) % 360.0
# Tolerance limited by stellar aberation
self.assertTrue(np.allclose(lst, TRA, atol=0.01, rtol=1e-10))
def test_sidereal_time_with_nonzero_delta_t(jd):
u = c.sidereal_time(jd.ut1, 0.0, jd.delta_t, False, True)
v = earthlib.sidereal_time(jd)
epsilon = 1e-13 # days; 14 digits of agreement
eq(u, v, epsilon)
