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This is the Python version of a demo to convert galactic coordinates to horizontal coordinates for a given time and geographic location.
77 lines
2.2 KiB
Python
Executable File
77 lines
2.2 KiB
Python
Executable File
#!/usr/bin/env python3
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#
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# galactic.py - by Don Cross - 2021-06-14
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#
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# Example Python program for Astronomy Engine:
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# https://github.com/cosinekitty/astronomy
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#
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# Demo of converting galactic coordinates to horizontal coordinates.
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#
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import sys
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import math
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from astronomy import *
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UsageText = r'''
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USAGE: galactic olat olon glat glon [yyyy-mm-ddThh:mm:ssZ]
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where
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olat = observer's latitude on the Earth
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olon = observer's longitude on the Earth
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glat = IAU 1958 galatic latitude of the target
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glon = IAU 1958 galatic longitude of the target
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yyyy-mm-ddThh:mm:ssZ = optional UTC date/time
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Given the galactic coordinates of a point source in the sky,
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this program calculates horizontal aiming coordinates for an
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observer on or near the Earth's surface.
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If the date/time is given on the command line, it is used.
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Otherwise, the computer's current date/time is used.
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'''
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def GalacticToHorizontal(time, observer, glat, glon):
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# Calculate a matrix that converts galactic coordinates
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# to J2000 equatorial coordinates.
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rot = Rotation_GAL_EQJ()
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# Adjust the rotation matrix to convert galactic to horizontal.
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adjust_rot = Rotation_EQJ_HOR(time, observer)
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rot = CombineRotation(rot, adjust_rot)
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# Convert the galactic coordinates from angles to a unit vector.
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gsphere = Spherical(glat, glon, 1.0)
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gvec = VectorFromSphere(gsphere, time)
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# Use the rotation matrix to convert the galactic vector to a horizontal vector.
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hvec = RotateVector(rot, gvec)
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# Convert the horizontal vector back to angular coordinates.
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# Assume this is a radio source (not optical), do not correct for refraction.
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hsphere = HorizonFromVector(hvec, Refraction.Airless)
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return hsphere.lat, hsphere.lon
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if __name__ == '__main__':
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if len(sys.argv) not in [5, 6]:
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print(UsageText)
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sys.exit(1)
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olat = float(sys.argv[1])
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olon = float(sys.argv[2])
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observer = Observer(olat, olon)
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glat = float(sys.argv[3])
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glon = float(sys.argv[4])
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if len(sys.argv) > 5:
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time = Time.Parse(sys.argv[5])
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else:
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time = Time.Now()
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altitude, azimuth = GalacticToHorizontal(time, observer, glat, glon)
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print('altitude = {:10.3f}, azimuth = {:10.3f}'.format(altitude, azimuth))
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sys.exit(0)
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