def __get_relative_prime_meridian(year):
"""
- total progression = 100d42.6 + cumulative prog + leap progs
- cumulative progression: delta(year-2001) * -0d14.31667
- leap progression: (leap years elapsed) * 0d59.0
:param year: observation year
:return: angle of prime meridian
"""
reference_rotation = Angle.from_string("100d42.6")
# cumulative progression: delta(year-2001) * -0d14.31667
annual_gha_decrement = Angle.from_string("-0d14.32")
delta_year = year - Aries.REFERENCE_YEAR
cumulative_progression = Angle.multiply(annual_gha_decrement,
delta_year)
# leap progression: (leap years elapsed) * 0d59.0
daily_rotation = Angle.from_string("0d59.0")
leap_years = math.floor((year - Aries.REFERENCE_YEAR) / 4)
leap_progression = Angle.multiply(daily_rotation, leap_years)
# total progression = 100d42.6 + cumulative prog + leap progs
total_progression = Angle.add(reference_rotation,
cumulative_progression)
total_progression = Angle.add(total_progression, leap_progression)
print("total progression" + total_progression.str)
return total_progression
