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Use mypy to check all Python demo programs. Updated the demos to pass type checking. There were a couple of small mistakes found, so this was worth the effort.
98 lines
4.2 KiB
Python
Executable File
98 lines
4.2 KiB
Python
Executable File
#!/usr/bin/env python3
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#
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# camera.py - by Don Cross - 2021-03-27
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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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# Suppose you want to photograph the Moon,
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# and you want to know what it will look like in the photo.
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# Given a location on the Earth, and a date/time,
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# this program calculates the orientation of the sunlit
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# side of the Moon with respect to the top of your
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# photo image. It assumes the camera faces directly
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# toward the Moon's azimuth and tilts upward to its
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# altitude angle above the horizon.
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#
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# To execute, run the command:
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#
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# python3 camera.py latitude longitude [yyyy-mm-ddThh:mm:ssZ]
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#
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import sys
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import math
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import astronomy
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from astro_demo_common import ParseArgs
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def Camera(observer: astronomy.Observer, time: astronomy.Time) -> int:
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tolerance = 1.0e-15
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# Calculate the topocentric equatorial coordinates of date for the Moon.
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# Assume aberration does not matter because the Moon is so close and has such a small relative velocity.
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moon_equ = astronomy.Equator(astronomy.Body.Moon, time, observer, True, False)
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# Also calculate the Sun's topocentric position in the same coordinate system.
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sun_equ = astronomy.Equator(astronomy.Body.Sun, time, observer, True, False)
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# Get the Moon's horizontal coordinates, so we know how much to pivot azimuth and altitude.
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moon_hor = astronomy.Horizon(time, observer, moon_equ.ra, moon_equ.dec, astronomy.Refraction.Airless)
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print('Moon horizontal position: azimuth = {:0.3f}, altitude = {:0.3f}'.format(moon_hor.azimuth, moon_hor.altitude))
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# Get the rotation matrix that converts equatorial to horizontal coordintes for this place and time.
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rot = astronomy.Rotation_EQD_HOR(time, observer)
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# Modify the rotation matrix in two steps:
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# First, rotate the orientation so we are facing the Moon's azimuth.
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# We do this by pivoting around the zenith axis.
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# Horizontal axes are: 0 = north, 1 = west, 2 = zenith.
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# Tricky: because the pivot angle increases counterclockwise, and azimuth
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# increases clockwise, we undo the azimuth by adding the positive value.
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rot = astronomy.Pivot(rot, 2, moon_hor.azimuth)
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# Second, pivot around the leftward axis to bring the Moon to the camera's altitude level.
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# From the point of view of the leftward axis, looking toward the camera,
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# adding the angle is the correct sense for subtracting the altitude.
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rot = astronomy.Pivot(rot, 1, moon_hor.altitude)
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# As a sanity check, apply this rotation to the Moon's equatorial (EQD) coordinates and verify x=0, y=0.
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vec = astronomy.RotateVector(rot, moon_equ.vec)
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# Convert to unit vector.
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radius = vec.Length()
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vec.x /= radius
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vec.y = abs(vec.y / radius) # prevent "-0"
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vec.z = abs(vec.z / radius) # prevent "-0"
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print('Moon check:', vec.format('0.8f'))
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if abs(vec.x - 1.0) > tolerance:
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print("Excessive error in moon check (x).")
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return 1
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if abs(vec.y) > tolerance:
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print("Excessive error in moon check (y).")
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return 1
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if abs(vec.z) > tolerance:
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print("Excessive error in moon check (z).")
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return 1
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# Apply the same rotation to the Sun's equatorial vector.
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# The x- and y-coordinates now tell us which side appears sunlit in the camera!
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vec = astronomy.RotateVector(rot, sun_equ.vec)
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# Don't bother normalizing the Sun vector, because in AU it will be close to unit anyway.
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print('Sun vector:', vec.format('0.8f'))
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# Calculate the tilt angle of the sunlit side, as seen by the camera.
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# The x-axis is now pointing directly at the object, z is up in the camera image, y is to the left.
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tilt = math.degrees(math.atan2(vec.y, vec.z))
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print('Tilt angle of sunlit side of the Moon = {:0.3f} degrees counterclockwise from up.'.format(tilt))
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illum = astronomy.Illumination(astronomy.Body.Moon, time)
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print('Moon magnitude = {:0.2f}, phase angle = {:0.2f} degrees.'.format(illum.mag, illum.phase_angle))
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angle = astronomy.AngleFromSun(astronomy.Body.Moon, time)
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print('Angle between Moon and Sun as seen from Earth = {:0.2f} degrees.'.format(angle))
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return 0
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if __name__ == '__main__':
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observer, time = ParseArgs(sys.argv)
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sys.exit(Camera(observer, time))
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