def declination(cls, tee, beta, lam):
"""Return declination at moment UT tee of object at
longitude 'lam' and latitude 'beta'."""
varepsilon = cls.obliquity(tee)
return arcsin_degrees(
(sin_degrees(beta) * cos_degrees(varepsilon)) +
(cos_degrees(beta) * sin_degrees(varepsilon) * sin_degrees(lam)))
def approx_moment_of_depression(self, tee, alpha, early):
"""Return the moment in local time near tee when depression angle
of sun is alpha (negative if above horizon) at location;
early is true when MORNING event is sought and false for EVENING.
Raise VlueError if depression angle is not reached."""
ttry = self.sine_offset(tee, alpha)
date = Clock.fixed_from_moment(tee)
if alpha >= 0:
if early:
alt = date
else:
alt = date + 1
else:
alt = date + Clock.days_from_hours(12)
if abs(ttry) > 1:
value = self.sine_offset(alt, alpha)
else:
value = ttry
if abs(value) <= 1:
temp = -1 if early else 1
temp *= mod(Clock.days_from_hours(12) + arcsin_degrees(value) / 360, 1) - Clock.days_from_hours(6)
temp += date + Clock.days_from_hours(12)
return self.local_from_apparent(temp)
else:
raise ValueError("Depression angle not reached")
def lunar_parallax(self, tee):
"""Return the parallax of moon at moment, tee, at location, location.
Adapted from "Astronomical Algorithms" by Jean Meeus,
Willmann_Bell, Inc., 1998."""
geo = self.lunar_altitude(tee)
Delta = Lunar.lunar_distance(tee)
alt = 6378140 / Delta
arg = alt * cos_degrees(geo)
return arcsin_degrees(arg)
def lunar_altitude(self, tee):
"""Return the geocentric altitude of moon at moment, tee,
at location, location, as a small positive/negative angle in degrees,
ignoring parallax and refraction. Adapted from 'Astronomical
Algorithms' by Jean Meeus, Willmann_Bell, Inc., 1998."""
lamb = Lunar.lunar_longitude(tee)
beta = Lunar.lunar_latitude(tee)
alpha = Astro.right_ascension(tee, beta, lamb)
delta = Astro.declination(tee, beta, lamb)
theta0 = Astro.sidereal_from_moment(tee)
cap_H = mod(theta0 + self.longitude - alpha, 360)
altitude = arcsin_degrees(
(sin_degrees(self.latitude) * sin_degrees(delta)) +
(cos_degrees(self.latitude) * cos_degrees(delta) * cos_degrees(cap_H)))
return mod(altitude + 180, 360) - 180
