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Diffstat (limited to 'src/ru/olamedia/astronomy/MoonPosition.java')
| -rw-r--r-- | src/ru/olamedia/astronomy/MoonPosition.java | 185 |
1 files changed, 185 insertions, 0 deletions
diff --git a/src/ru/olamedia/astronomy/MoonPosition.java b/src/ru/olamedia/astronomy/MoonPosition.java new file mode 100644 index 0000000..e20349f --- /dev/null +++ b/src/ru/olamedia/astronomy/MoonPosition.java @@ -0,0 +1,185 @@ +package ru.olamedia.astronomy; + +/* + * Copyright 2011 Brad Parks + * + * Licensed under the Apache License, Version 2.0 (the "License"); + * you may not use this file except in compliance with the License. + * You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +//package com.bradsbrain.simpleastronomy; + +import static ru.olamedia.astronomy.BaseUtils.sinDegrees; + +import java.util.Calendar; + +public class MoonPosition { + // some handy constants + private double EPOCH = 2447891.5; // 1990 January 0.0 + private double MEAN_LONGITUDE_AT_EPOCH = 318.351648; + private double MEAN_LONGITUDE_OF_PERIGREE_AT_EPOCH = 36.340410; + + /** + * The True Longitude + */ + private double trueOrbitalLongitude; + + /** + * This is from section 65, page 144 + * + * @param cal + * the calendar date for which to compute the moon position + */ + public MoonPosition(Calendar cal) { + Calendar myCal = BaseUtils.getSafeLocalCopy(cal.getTimeInMillis()); + double daysSince = BaseUtils.exactDaysSince(myCal, EPOCH); + + // l + double moonMeanLongitude = computeMeanLongitude(daysSince); + // M m + double moonMeanAnomaly = computeMeanAnomaly(daysSince, + moonMeanLongitude); + + SunPosition sunPos = new SunPosition(myCal); + + MoonCorrections corrections = new MoonCorrections(moonMeanLongitude, + moonMeanAnomaly, sunPos.getEclipticLongitude(), + sunPos.getMeanAnomaly()); + trueOrbitalLongitude = corrections.getCorrectedLongitude() + - corrections.getVariationCorrection(); + } + + public double getTrueLongitude() { + return trueOrbitalLongitude; + } + + /** + * Compute the Moon Mean Longitude l + * + * @param daysSince + * @return + */ + private double computeMeanLongitude(double daysSince) { + double moonMeanLongitude = 13.1763966 * daysSince + + MEAN_LONGITUDE_AT_EPOCH; + return BaseUtils.adjustTo360Range(moonMeanLongitude); + } + + /** + * Compute the Moon Mean Anomaly M m + * + * @param daysSince + * @param moonMeanLongitude + * @return + */ + private double computeMeanAnomaly(double daysSince, double moonMeanLongitude) { + double moonMeanAnomaly = moonMeanLongitude - (0.1114041 * daysSince) + - MEAN_LONGITUDE_OF_PERIGREE_AT_EPOCH; + return BaseUtils.adjustTo360Range(moonMeanAnomaly); + } + + /** + * Private internal class used for lots of computations and corrections + */ + private static class MoonCorrections { + private double moonMeanLongitude; + private double moonMeanAnomaly; + private double sunLongitude; + private double sunMeanAnomaly; + + MoonCorrections(double moonMeanLongitude, double moonMeanAnomaly, + double sunLongitude, double sunMeanAnomaly) { + this.moonMeanAnomaly = moonMeanAnomaly; + this.sunMeanAnomaly = sunMeanAnomaly; + this.moonMeanLongitude = moonMeanLongitude; + this.sunLongitude = sunLongitude; + } + + /** + * V + * + * @return + */ + public double getVariationCorrection() { + return 0.6583 * sinDegrees(2 * (getCorrectedLongitude() - sunLongitude)); + } + + /** + * l' + * + * @return + */ + public double getCorrectedLongitude() { + return moonMeanLongitude + getEvictionCorrection() + + getCorrectionForEquationCentre() + - getAnnualEquationCorrection() + + getYetAnotherCorrectionTerm(); + } + + /** + * A 4 + * + * @return + */ + private double getYetAnotherCorrectionTerm() { + return 0.214 * sinDegrees(2 * getMoonCorrectedAnomaly()); + } + + /** + * E c + * + * @return + */ + private double getCorrectionForEquationCentre() { + return 6.2886 * sinDegrees(getMoonCorrectedAnomaly()); + } + + /** + * M' m + * + * @return + */ + private double getMoonCorrectedAnomaly() { + return moonMeanAnomaly + getEvictionCorrection() + - getAnnualEquationCorrection() + - getUnnamedThirdCorrection(); + } + + /** + * E v + * + * @return + */ + public double getEvictionCorrection() { + double C = moonMeanLongitude - sunLongitude; + return 1.2739 * sinDegrees(2.0 * C - moonMeanAnomaly); + } + + /** + * A e + * + * @return + */ + public double getAnnualEquationCorrection() { + return 0.1858 * sinDegrees(sunMeanAnomaly); + } + + /** + * A 3 + * + * @return + */ + public double getUnnamedThirdCorrection() { + return 0.37 * sinDegrees(sunMeanAnomaly); + } + } + +}
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