diff options
| -rw-r--r-- | src/plugins/lunar.py | 78 |
1 files changed, 43 insertions, 35 deletions
diff --git a/src/plugins/lunar.py b/src/plugins/lunar.py index c193369..43f707a 100644 --- a/src/plugins/lunar.py +++ b/src/plugins/lunar.py @@ -21,48 +21,56 @@ import math import time -def julian_day(t): +class Lunar: ''' - Converts a POSIX time timestamp to a Julian Day timestamp + Lunar observation - @param t:float The time in POSIX time - @return :float The time in Julian Days + @variable fraction:float The phase of the moon increasing linearly. 0 on new moon, 0,5 on + full moon. ]0, 0,5[ when waxing and ]0m5, 1[ when waning. + @variable waxing:bool `True` when moon is waxing (increasing illumination) and `False` + when waning (decreasing). Not well defined on new moon (fraction = 0, + illumination = 0) and full moon (fraction = 0,5, illumination = 1). + @variable terminator:float The latitude, as seen from the northern hemisphere on Earth, of the + terminator. The terminator is the line delimiting the sunlit area + and the dark area. + @variable illumination:float The illumnation of the moon, the fraction of the visible side's + area that is sunlit ''' - return t / 86400.0 + 2440587.5 - -def radians(deg): + + REFERENCE_NEW_MOON = 934329600 # 11 August 1999 00:00:00 UTC + ''' + :float Time of last known new moon, in POSIX time ''' - Convert an angle from degrees to radians - @param deg:float The angle in degrees - @return :float The angle in radians + SYNODIC_MONTH = 29.530588853 ''' - return deg * math.pi / 180 - -ref = julian_day(934329600) # 11 August 1999 00:00:00 UTC -now = julian_day(time.time()) -synodic_month = 29.530588853 - -# TODO how to we calculate the Moon's apparent geocentric celestial longitude -fraction = ((now - ref) / synodic_month) % 1 -waxing = fraction <= 0.5 # we get an off by one without equality -print('fraction: %f' % fraction) -print('waxing' if waxing else 'waning') - -terminator = 90 - 360 * fraction # sunlit trailing -if terminator < -90: - terminator += 180 # visible side -print('terminator: %f°' % terminator) - -hacoversin = lambda deg : 0.5 - math.sin(radians(deg)) / 2 - -inverted = terminator < 0 -illumination = hacoversin(abs(terminator)) - -if (not waxing) != inverted: - illumination = 1 - illumination + :float The length of a lunar month, in days + ''' + + def __init__(self): + ''' + Constructor + ''' + julian_day = lambda t : t / 86400.0 + 2440587.5 + radians = lambda deg : deg * math.pi / 180 + hacoversin = lambda deg : 0.5 - math.sin(radians(deg)) / 2 + + ref = julian_day(Lunar.REFERENCE_NEW_MOON) + now = julian_day(time.time()) + + # TODO how to we calculate the Moon's apparent geocentric celestial longitude + self.fraction = ((now - ref) / Lunar.SYNODIC_MONTH) % 1 + self.waxing = self.fraction <= 0.5 # we get an off by one without equality + + self.terminator = 90 - 360 * fraction # sunlit trailing + if self.terminator < -90: + self.terminator += 180 # visible side + + inverted = self.terminator < 0 + self.illumination = hacoversin(abs(self.terminator)) + if (not self.waxing) != inverted: + self.illumination = 1 - self.illumination -print('illumination: %.2f%%' % (illumination * 100)) # TODO add libration # TODO add phase names |