def equinox(jd, season, delta):
"""Return the precise moment of an equinox or solstice event on Earth.
Parameters:
- `jd` : Julian of an approximate time of the event in dynamical time
- `season` : one of ("spring", "summer", "autumn", "winter")
- `delta` : the required precision in days. Times accurate to a second
are reasonable when using the VSOP model.
Returns:
- Julian Day : (int) dynamical time
"""
#
# If we knew that the starting approximate time was close enough
# to the actual time, we could pull nutation_in_longitude() and the
# aberration out of the loop and save some calculating.
#
circ = _circle[season]
sun = Sun()
for i in range(20):
jd0 = jd
L, B, R = sun.dimension3(jd)
L += nutation_in_longitude(jd) + aberration_low(R)
L, B = vsop_to_fk5(jd, L, B)
# Meeus uses jd + 58 * sin(diff(...))
jd += diff_angle(L, circ) * _k_sun_motion
if abs(jd - jd0) < delta:
return jd
raise Error("bailout")
def equinox(jd, season, delta):
"""Return the precise moment of an equinox or solstice event on Earth.
Parameters:
- `jd` : Julian of an approximate time of the event in dynamical time
- `season` : one of ("spring", "summer", "autumn", "winter")
- `delta` : the required precision in days. Times accurate to a second
are reasonable when using the VSOP model.
Returns:
- Julian Day : (int) dynamical time
"""
#
# If we knew that the starting approximate time was close enough
# to the actual time, we could pull nutation_in_longitude() and the
# aberration out of the loop and save some calculating.
#
circ = _circle[season]
sun = Sun()
for i in range(20):
jd0 = jd
L, B, R = sun.dimension3(jd)
L += nutation_in_longitude(jd) + aberration_low(R)
L, B = vsop_to_fk5(jd, L, B)
# Meeus uses jd + 58 * sin(diff(...))
jd += diff_angle(L, circ) * _k_sun_motion
if abs(jd - jd0) < delta:
return jd
raise Error("bailout")
def _longitude(self, jd):
"""Return the geocentric ecliptic longitude in radians.
"""
from astronomia.nutation import nutation_in_longitude
T = jd_to_jcent(jd)
L1, D, M, M1, F, A1, A2, A3, E, E2 = _constants(T)
lsum = 0.0
for tD, tM, tM1, tF, tl, tr in _tblLR:
arg = tD * D + tM * M + tM1 * M1 + tF * F
if abs(tM) == 1:
tl *= E
elif abs(tM) == 2:
tl *= E2
lsum += tl * np.sin(arg)
lsum += 3958*np.sin(A1) + 1962*np.sin(L1 - F) + 318*np.sin(A2)
nutinlong = nutation_in_longitude(jd)
longitude = L1 + d_to_r(lsum / 1000000) + nutinlong
return longitude
def _longitude(self, jd):
"""Return the geocentric ecliptic longitude in radians.
"""
from astronomia.nutation import nutation_in_longitude
T = jd_to_jcent(jd)
L1, D, M, M1, F, A1, A2, A3, E, E2 = _constants(T)
lsum = 0.0
for tD, tM, tM1, tF, tl, tr in _tblLR:
arg = tD * D + tM * M + tM1 * M1 + tF * F
if abs(tM) == 1:
tl *= E
elif abs(tM) == 2:
tl *= E2
lsum += tl * np.sin(arg)
lsum += 3958 * np.sin(A1) + 1962 * np.sin(L1 - F) + 318 * np.sin(A2)
nutinlong = nutation_in_longitude(jd)
longitude = L1 + d_to_r(lsum / 1000000) + nutinlong
return longitude
