def phasis_on_or_before(self, date):
"""Return the closest fixed date on or before date 'date', when crescent
moon first became visible at location 'location'."""
mean = date - ifloor(Lunar.lunar_phase(date + 1) / 360.0 * Lunar.MEAN_SYNODIC_MONTH)
tau = ((mean - 30)
if (((date - mean) <= 3) and (not self.visible_crescent(date)))
else (mean - 2))
return next_int(tau, lambda d: self.visible_crescent(d))
def visible_crescent(self, date):
"""Return S. K. Shaukat's criterion for likely
visibility of crescent moon on eve of date 'date',
at location 'location'."""
tee = self.universal_from_standard(self.dusk(date - 1, mpf(4.5)))
phase = Lunar.lunar_phase(tee)
altitude = self.lunar_altitude(tee)
arc_of_light = arccos_degrees(cos_degrees(Lunar.lunar_latitude(tee)) * cos_degrees(phase))
return ((Lunar.NEW < phase < Lunar.FIRST_QUARTER) and
(mpf(10.6) <= arc_of_light <= 90) and
(altitude > mpf(4.1)))
def moonrise(self, date):
"""Return the standard time of moonrise on fixed, date,
and location, location."""
t = self.universal_from_standard(date)
waning = (Lunar.lunar_phase(t) > 180)
alt = self.observed_lunar_altitude(t)
offset = alt / 360
if waning and (offset > 0):
approx = t + 1 - offset
elif waning:
approx = t - offset
else:
approx = t + (1 / 2) + offset
rise = binary_search(approx - Clock.days_from_hours(3),
approx + Clock.days_from_hours(3),
lambda u, l: ((u - l) < Clock.days_from_hours(1/60)),
lambda x: self.observed_lunar_altitude(x) > 0)
if rise < (t + 1):
return self.standard_from_universal(rise)
raise ValueError()
def phasis_on_or_after(cls, fixed_date, location):
"""Return closest fixed date on or after date, date, on the eve
of which crescent moon first became visible at location, location."""
mean = fixed_date - ifloor(Lunar.lunar_phase(fixed_date + 1) / mpf(360) * Lunar.MEAN_SYNODIC_MONTH)
tau = fixed_date if fixed_date - mean <= 3 and not location.visible_crescent(fixed_date - 1) else mean + 29
return next_int(tau, lambda d: location.visible_crescent(d))
