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5eca7d7760
Updated CodeQL config to ignore source templates, because they are not syntactically valid source code. Ignore other stuff that is irrelevant to published code quality. Made various fixes based on helpful CodeQL analysis.
82 lines
3.0 KiB
Python
Executable File
82 lines
3.0 KiB
Python
Executable File
#!/usr/bin/env python3
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#
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# constellation.py - Don Cross - 2021-04-30 Fri
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#
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# Searches for the moon moving into different constellations.
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# This is an example of doing a search for the time of transition
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# of a body from one constellation to another.
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#
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import sys
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from astronomy import Time, Body, Constellation, GeoVector, EquatorFromVector
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#------------------------------------------------------------------------------
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def BodyConstellation(body, time):
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vec = GeoVector(body, time, False)
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equ = EquatorFromVector(vec)
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return Constellation(equ.ra, equ.dec)
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#------------------------------------------------------------------------------
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def FindConstellationChange(body, c1, t1, t2):
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# Do a binary search to find what time between t1 and t2
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# is the boundary between being in constellation c1 and some other
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# constellation. Return the tuple (tx, cx), where tx is the
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# transition time, and cx is the constellation we are moving into.
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tolerance = 0.1 / (24.0 * 3600.0) # one tenth of a second
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while True:
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dt = t2.ut - t1.ut
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tx = t1.AddDays(dt/2)
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cx = BodyConstellation(body, tx)
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if cx.symbol == c1.symbol:
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t1 = tx
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else:
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if dt < tolerance:
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# Always end the search inside the new constellation.
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return (tx, cx)
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t2 = tx
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#------------------------------------------------------------------------------
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def FindConstellationChanges(body, startTime, stopTime, dayIncrement):
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t1 = startTime
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c1 = BodyConstellation(body, t1)
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while t1 < stopTime:
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t2 = t1.AddDays(dayIncrement)
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c2 = BodyConstellation(body, t2)
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if c1.symbol != c2.symbol:
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# The body moved from one constellation to another during this time step.
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# Narrow in on the exact moment by doing a binary search.
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tx, cx = FindConstellationChange(body, c1, t1, t2)
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print('{} : {} leaves {} and enters {}.'.format(tx, body.name, c1.name, cx.name))
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c1 = cx
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t1 = tx
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else:
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# No constellation change in this time step. Try again on the next time step.
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c1 = c2
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t1 = t2
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return 0
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#------------------------------------------------------------------------------
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if __name__ == '__main__':
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if len(sys.argv) == 1:
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startTime = Time.Now()
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elif len(sys.argv) == 2:
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startTime = Time.Parse(sys.argv[1])
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else:
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print('USAGE: {} [yyyy-mm-ddThh:mm:ssZ]'.format(sys.argv[0]))
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sys.exit(1)
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stopTime = startTime.AddDays(30.0)
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# There are 12 zodiac constellations, and the moon takes
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# about 27.3 days in its sidereal period. Therefore, there
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# are roughly 2.2 days per constellation. We will sample
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# the Moon's constellation once every 0.1 days to reduce
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# the chance of missing a brief transition through a small
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# part of a constellation.
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dayIncrement = 0.1
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rc = FindConstellationChanges(Body.Moon, startTime, stopTime, dayIncrement)
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sys.exit(rc)
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