400 lines
11 KiB
Python
400 lines
11 KiB
Python
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# -*- coding: utf-8 -*-
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# PyMeeus: Python module implementing astronomical algorithms.
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# Copyright (C) 2018 Dagoberto Salazar
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#
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# This program is free software: you can redistribute it and/or modify
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# it under the terms of the GNU Lesser General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU Lesser General Public License for more details.
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#
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# You should have received a copy of the GNU Lesser General Public License
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# along with this program. If not, see <https://www.gnu.org/licenses/>.
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from math import sin, cos, sqrt, asin, atan2
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from pymeeus.Angle import Angle
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from pymeeus.Epoch import Epoch, JDE2000
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from pymeeus.Sun import Sun
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"""
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.. module:: Pluto
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:synopsis: Class to model Pluto minor planet
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:license: GNU Lesser General Public License v3 (LGPLv3)
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.. moduleauthor:: Dagoberto Salazar
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"""
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PLUTO_ARGUMENT = [
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(0.0, 0.0, 1.0),
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(0.0, 0.0, 2.0),
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(0.0, 0.0, 3.0),
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(0.0, 0.0, 4.0),
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(0.0, 0.0, 5.0),
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(0.0, 0.0, 6.0),
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(0.0, 1.0, -1.0),
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(0.0, 1.0, 0.0),
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(0.0, 1.0, 1.0),
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(0.0, 1.0, 2.0),
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(0.0, 1.0, 3.0),
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(0.0, 2.0, -2.0),
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(0.0, 2.0, -1.0),
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(0.0, 2.0, 0.0),
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(1.0, -1.0, 0.0),
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(1.0, -1.0, 1.0),
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(1.0, 0.0, -3.0),
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(1.0, 0.0, -2.0),
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(1.0, 0.0, -1.0),
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(1.0, 0.0, 0.0),
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(1.0, 0.0, 1.0),
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(1.0, 0.0, 2.0),
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(1.0, 0.0, 3.0),
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(1.0, 0.0, 4.0),
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(1.0, 1.0, -3.0),
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(1.0, 1.0, -2.0),
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(1.0, 1.0, -1.0),
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(1.0, 1.0, 0.0),
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(1.0, 1.0, 1.0),
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(1.0, 1.0, 3.0),
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(2.0, 0.0, -6.0),
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(2.0, 0.0, -5.0),
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(2.0, 0.0, -4.0),
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(2.0, 0.0, -3.0),
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(2.0, 0.0, -2.0),
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(2.0, 0.0, -1.0),
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(2.0, 0.0, 0.0),
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(2.0, 0.0, 1.0),
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(2.0, 0.0, 2.0),
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(2.0, 0.0, 3.0),
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(3.0, 0.0, -2.0),
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(3.0, 0.0, -1.0),
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(3.0, 0.0, 0.0)
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]
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"""This table contains Pluto's argument coefficients according to Table 37.A in
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Meeus' book, page 265."""
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PLUTO_LONGITUDE = [
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(-19799805.0, 19850055.0),
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(897144.0, -4954829.0),
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(611149.0, 1211027.0),
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(-341243.0, -189585.0),
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(129287.0, -34992.0),
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(-38164.0, 30893.0),
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(20442.0, -9987.0),
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(-4063.0, -5071.0),
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(-6016.0, -3336.0),
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(-3956.0, 3039.0),
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(-667.0, 3572.0),
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(1276.0, 501.0),
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(1152.0, -917.0),
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(630.0, -1277.0),
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(2571.0, -459.0),
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(899.0, -1449.0),
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(-1016.0, 1043.0),
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(-2343.0, -1012.0),
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(7042.0, 788.0),
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(1199.0, -338.0),
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(418.0, -67.0),
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(120.0, -274.0),
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(-60.0, -159.0),
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(-82.0, -29.0),
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(-36.0, -29.0),
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(-40.0, 7.0),
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(-14.0, 22.0),
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(4.0, 13.0),
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(5.0, 2.0),
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(-1.0, 0.0),
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(2.0, 0.0),
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(-4.0, 5.0),
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(4.0, -7.0),
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(14.0, 24.0),
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(-49.0, -34.0),
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(163.0, -48.0),
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(9.0, -24.0),
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(-4.0, 1.0),
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(-3.0, 1.0),
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(1.0, 3.0),
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(-3.0, -1.0),
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(5.0, -3.0),
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(0.0, 0.0)
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]
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"""This table contains the periodic terms to compute Pluto's heliocentric
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longitude according to Table 37.A in Meeus' book, page 265"""
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PLUTO_LATITUDE = [
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(-5452852.0, -14974862),
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(3527812.0, 1672790.0),
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(-1050748.0, 327647.0),
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(178690.0, -292153.0),
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(18650.0, 100340.0),
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(-30697.0, -25823.0),
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(4878.0, 11248.0),
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(226.0, -64.0),
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(2030.0, -836.0),
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(69.0, -604.0),
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(-247.0, -567.0),
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(-57.0, 1.0),
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(-122.0, 175.0),
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(-49.0, -164.0),
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(-197.0, 199.0),
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(-25.0, 217.0),
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(589.0, -248.0),
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(-269.0, 711.0),
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(185.0, 193.0),
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(315.0, 807.0),
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(-130.0, -43.0),
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(5.0, 3.0),
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(2.0, 17.0),
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(2.0, 5.0),
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(2.0, 3.0),
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(3.0, 1.0),
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(2.0, -1.0),
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(1.0, -1.0),
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(0.0, -1.0),
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(0.0, 0.0),
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(0.0, -2.0),
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(2.0, 2.0),
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(-7.0, 0.0),
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(10.0, -8.0),
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(-3.0, 20.0),
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(6.0, 5.0),
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(14.0, 17.0),
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(-2.0, 0.0),
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(0.0, 0.0),
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(0.0, 0.0),
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(0.0, 1.0),
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(0.0, 0.0),
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(1.0, 0.0)
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]
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"""This table contains the periodic terms to compute Pluto's heliocentric
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latitude according to Table 37.A in Meeus' book, page 265"""
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PLUTO_RADIUS_VECTOR = [
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(66865439.0, 68951812.0),
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(-11827535.0, -332538.0),
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(1593179.0, -1438890.0),
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(-18444.0, 483220.0),
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(-65977.0, -85431.0),
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(31174.0, -6032.0),
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(-5794.0, 22161.0),
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(4601.0, 4032.0),
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(-1729.0, 234.0),
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(-415.0, 702.0),
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(239.0, 723.0),
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(67.0, -67.0),
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(1034.0, -451.0),
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(-129.0, 504.0),
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(480.0, -231.0),
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(2.0, -441.0),
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(-3359.0, 265.0),
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(7856.0, -7832.0),
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(36.0, 45763.0),
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(8663.0, 8547.0),
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(-809.0, -769.0),
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(263.0, -144.0),
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(-126.0, 32.0),
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(-35.0, -16.0),
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(-19.0, -4.0),
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(-15.0, 8.0),
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(-4.0, 12.0),
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(5.0, 6.0),
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(3.0, 1.0),
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(6.0, -2.0),
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(2.0, 2.0),
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(-2.0, -2.0),
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(14.0, 13.0),
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(-63.0, 13.0),
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(136.0, -236.0),
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(273.0, 1065.0),
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(251.0, 149.0),
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(-25.0, -9.0),
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(9.0, -2.0),
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(-8.0, 7.0),
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(2.0, -10.0),
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(19.0, 35.0),
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(10.0, 3.0)
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]
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"""This table contains the periodic terms to compute Pluto's heliocentric
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radius vector according to Table 37.A in Meeus' book, page 265"""
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class Pluto(object):
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"""
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Class Pluto models that minor planet.
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"""
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@staticmethod
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def geometric_heliocentric_position(epoch):
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"""This method computes the geometric heliocentric position of planet
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Pluto for a given epoch.
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:param epoch: Epoch to compute Pluto position, as an Epoch object
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:type epoch: :py:class:`Epoch`
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:returns: A tuple with the heliocentric longitude and latitude (as
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:py:class:`Angle` objects), and the radius vector (as a float,
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in astronomical units), in that order
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:rtype: tuple
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:raises: TypeError if input value is of wrong type.
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:raises: ValueError if input epoch outside the 1885-2099 range.
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>>> epoch = Epoch(1992, 10, 13.0)
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>>> l, b, r = Pluto.geometric_heliocentric_position(epoch)
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>>> print(round(l, 5))
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232.74071
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>>> print(round(b, 5))
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14.58782
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>>> print(round(r, 6))
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29.711111
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"""
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# First check that input value is of correct types
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if not isinstance(epoch, Epoch):
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raise TypeError("Invalid input type")
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# Check that the input epoch is within valid range
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y = epoch.year()
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if y < 1885.0 or y > 2099.0:
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raise ValueError("Epoch outside the 1885-2099 range")
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t = (epoch - JDE2000) / 36525.0
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jj = 34.35 + 3034.9057 * t
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ss = 50.08 + 1222.1138 * t
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pp = 238.96 + 144.96 * t
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# Compute the arguments
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corr_lon = 0.0
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corr_lat = 0.0
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corr_rad = 0.0
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for n, argument in enumerate(PLUTO_ARGUMENT):
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iii, jjj, kkk = argument
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alpha = Angle(iii * jj + jjj * ss + kkk * pp).to_positive()
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alpha = alpha.rad()
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sin_a = sin(alpha)
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cos_a = cos(alpha)
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a_lon, b_lon = PLUTO_LONGITUDE[n]
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corr_lon += a_lon * sin_a + b_lon * cos_a
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a_lat, b_lat = PLUTO_LATITUDE[n]
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corr_lat += a_lat * sin_a + b_lat * cos_a
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a_rad, b_rad = PLUTO_RADIUS_VECTOR[n]
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corr_rad += a_rad * sin_a + b_rad * cos_a
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# The coefficients in the tables were scaled up. Let's scale them down
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corr_lon /= 1000000.0
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corr_lat /= 1000000.0
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corr_rad /= 10000000.0
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lon = Angle(238.958116 + 144.96 * t + corr_lon)
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lat = Angle(-3.908239 + corr_lat)
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radius = 40.7241346 + corr_rad
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return lon, lat, radius
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@staticmethod
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def geocentric_position(epoch):
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"""This method computes the geocentric position of Pluto (right
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ascension and declination) for the given epoch, for the standard
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equinox J2000.0.
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:param epoch: Epoch to compute geocentric position, as an Epoch object
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:type epoch: :py:class:`Epoch`
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:returns: A tuple containing the right ascension and the declination as
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Angle objects
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:rtype: tuple
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:raises: TypeError if input value is of wrong type.
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:raises: ValueError if input epoch outside the 1885-2099 range.
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>>> epoch = Epoch(1992, 10, 13.0)
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>>> ra, dec = Pluto.geocentric_position(epoch)
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>>> print(ra.ra_str(n_dec=1))
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15h 31' 43.7''
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>>> print(dec.dms_str(n_dec=0))
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-4d 27' 29.0''
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"""
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# First check that input value is of correct types
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if not isinstance(epoch, Epoch):
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raise TypeError("Invalid input type")
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# Check that the input epoch is within valid range
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y = epoch.year()
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if y < 1885.0 or y > 2099.0:
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raise ValueError("Epoch outside the 1885-2099 range")
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# Compute the heliocentric position of Pluto
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ll, b, r = Pluto.geometric_heliocentric_position(epoch)
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# Change angles to radians
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ll = ll.rad()
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b = b.rad()
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# Values corresponding to obliquity of ecliptic (epsilon) for J2000.0
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sine = 0.397777156
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cose = 0.917482062
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x = r * cos(ll) * cos(b)
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y = r * (sin(ll) * cos(b) * cose - sin(b) * sine)
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z = r * (sin(ll) * cos(b) * sine + sin(b) * cose)
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# Compute Sun's J2000.0 rectacngular coordinates
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xs, ys, zs = Sun.rectangular_coordinates_j2000(epoch)
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# Compute auxiliary quantities
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xi = x + xs
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eta = y + ys
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zeta = z + zs
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# Compute Pluto's distance to Earth
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delta = sqrt(xi * xi + eta * eta + zeta * zeta)
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# Get the light-time difference
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tau = 0.0057755183 * delta
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# Repeat the computations using the light-time correction
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ll, b, r = Pluto.geometric_heliocentric_position(epoch - tau)
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# Change angles to radians
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ll = ll.rad()
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b = b.rad()
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x = r * cos(ll) * cos(b)
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y = r * (sin(ll) * cos(b) * cose - sin(b) * sine)
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z = r * (sin(ll) * cos(b) * sine + sin(b) * cose)
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# Compute auxiliary quantities
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xi = x + xs
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eta = y + ys
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zeta = z + zs
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# Compute Pluto's distance to Earth
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delta = sqrt(xi * xi + eta * eta + zeta * zeta)
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# Compute right ascension and declination
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alpha = Angle(atan2(eta, xi), radians=True)
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dec = Angle(asin(zeta / delta), radians=True)
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return alpha.to_positive(), dec
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def main():
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# Let's define a small helper function
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def print_me(msg, val):
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print("{}: {}".format(msg, val))
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# Let's show some uses of Pluto class
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print("\n" + 35 * "*")
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print("*** Use of Pluto class")
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print(35 * "*" + "\n")
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# Let's now compute the heliocentric position for a given epoch
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epoch = Epoch(1992, 10, 13.0)
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lon, lat, r = Pluto.geometric_heliocentric_position(epoch)
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print_me("Geometric Heliocentric Longitude", lon.to_positive())
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print_me("Geometric Heliocentric Latitude", lat)
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print_me("Radius vector", r)
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print("")
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# Compute the geocentric position for 1992/10/13:
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epoch = Epoch(1992, 10, 13.0)
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ra, dec = Pluto.geocentric_position(epoch)
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print_me("Right ascension", ra.ra_str(n_dec=1))
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print_me("Declination", dec.dms_str(n_dec=1))
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if __name__ == "__main__":
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main()
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