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#!/usr/bin/python3
# XXX: can be written in 5 lines of Python with Skyfield:
#
# https://rhodesmill.org/skyfield/almanac.html#phases-of-the-moon
#
# Valhalla did something like this with the "astral" package:
#
# https://git.trueelena.org/software/pdfscripts/tree/planner/planner_generator.py?id=a8c5954f9c48a2485f3d198a949268ba78f1b339#n266
# https://github.com/sffjunkie/astral
#
# RFP filed in Debian:
# https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=911646
"""
Show moon phases for a given year.
All times returned are local. Use the TZ variable to change.
"""
import argparse
from collections import namedtuple
from itertools import cycle
import ephem
MoonPhase = namedtuple("MoonPhase", "name motion target")
# logic extracted from ephem.next_new_moon() and following next*
# functions
moon_phases = (
MoonPhase("new", ephem.twopi, 0),
MoonPhase("first", ephem.twopi, ephem.halfpi),
MoonPhase("full", ephem.twopi, ephem.pi),
MoonPhase("third", ephem.twopi, ephem.pi + ephem.halfpi),
)
def find_sequence(date):
"""find the first moon after the given date
PyEphem only gives us mechanisms to find the next X type of moon,
not *any* moon. So we need to know the *first* kind of moon we
will get (regardless of type).
Then range_phases can iterate over those in the proper order
starting from the date.
>>> [ phase.name for phase in find_sequence('2018') ]
['full', 'third', 'new', 'first']
>>> [ phase.name for phase in find_sequence('2019') ]
['new', 'first', 'full', 'third']
>>> [ phase.name for phase in find_sequence('2020') ]
['first', 'full', 'third', 'new']
>>> [ phase.name for phase in find_sequence('2021') ]
['third', 'new', 'first', 'full']
"""
dates = [
(ephem._find_moon_phase(date, phase.motion, phase.target), phase)
for phase in moon_phases
]
return [phase for date, phase in sorted(dates)]
def range_phases(start, end, sequence):
"""generate the moon phases in the given range"""
p = start
for phase in cycle(sequence):
p = ephem._find_moon_phase(p, phase.motion, phase.target)
if p > end:
break
yield p, phase
def main(start, end=None):
"""Test data was checked against:
https://www.timeanddate.com/moon/phases/canada/montreal?year=...
Current year, starts with a full moon:
>>> main('2018') # doctest: +ELLIPSIS
2018-01-01 21:24:05 full
2018-01-08 17:25:16 third
2018-01-16 21:17:14 new
2018-01-24 17:20:23 first
2018-01-31 08:26:44 full
2018-02-07 10:53:56 third
...
2018-11-29 19:18:49 third
2018-12-07 02:20:21 new
2018-12-15 06:49:15 first
2018-12-22 12:48:35 full
2018-12-29 04:34:18 third
Test year, does not:
>>> main('2009') # doctest: +ELLIPSIS
2009-01-04 06:56:15 first
2009-01-10 22:26:46 full
2009-01-17 21:45:45 third
2009-01-26 02:55:18 new
2009-02-02 18:13:08 first
...
2009-11-24 16:39:14 first
2009-12-02 02:30:27 full
2009-12-08 19:13:20 third
2009-12-16 07:02:06 new
2009-12-24 12:35:58 first
2009-12-31 14:12:45 full
Another test:
>>> main('2042') # doctest: +ELLIPSIS
2042-01-06 03:53:29 full
2042-01-14 06:24:00 third
2042-01-21 15:41:39 new
2042-01-28 07:48:09 first
2042-02-04 20:57:20 full
...
2042-11-27 01:05:33 full
2042-12-04 04:18:21 third
2042-12-12 09:29:13 new
2042-12-19 19:27:06 first
2042-12-26 12:42:16 full
"""
if start is None:
start = ephem.now()
else:
start = ephem.Date(start)
if end is None:
# dates are in days (float). this adds a year
end = start + 30.0
else:
end = ephem.Date(end)
sequence = find_sequence(start)
for date, phase in range_phases(start, end, sequence):
print("{:%Y-%m-%d %H:%M:%S} {.name}".format(ephem.localtime(date), phase))
if __name__ == "__main__":
parser = argparse.ArgumentParser(
description=__doc__, epilog="Should be rewritten with Skyfield."
)
parser.add_argument("start", nargs="?", help="start date (default: now)")
parser.add_argument("end", nargs="?", help="end date (default: next 30 days)")
args = parser.parse_args()
main(args.start, args.end)
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