1 files changed, 95 insertions, 0 deletions
diff --git a/src/ru/olamedia/astronomy/SunPosition.java b/src/ru/olamedia/astronomy/SunPosition.java
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+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 java.util.Calendar;
+
+public class SunPosition {
+	// some handy constants
+	private double EPOCH = 2447891.5; // 1990 January 0.0
+	private double ECLIPTIC_LONGITUDE_OF_PERIGREE = 282.768422;
+	private double ECLIPTIC_LONGITUDE_AT_EPOCH_1990 = 279.403303;
+	private double ECCENTRICITY_OF_ORBIT = 0.016713;
+
+	/**
+	 * The geocentric ecliptic longitude. <br>
+	 * Calculation is good to 3 decimal places <br>
+	 * me: 337.44406603442917, book: 337.444194
+	 */
+	private double geoEclipticLongitude = 0; // oft represented as a lambda with
+												// little circle+dot
+	/**
+	 * The mean anomaly
+	 */
+	private double meanAnomaly = 0; // oft represented as capital M with little
+									// circle+dot
+
+	public SunPosition(Calendar cal) {
+		Calendar myCal = BaseUtils.getSafeLocalCopy(cal.getTimeInMillis());
+
+		double daysSince = BaseUtils.exactDaysSince(myCal, EPOCH);
+
+		double N = (360 / 365.242191 * daysSince) % 360;
+		if (N < 0) {
+			N += 360;
+		}
+
+		meanAnomaly = computeMeanAnomaly(N);
+		geoEclipticLongitude = computeGeoEclipticLongitude(N);
+	}
+
+	private double computeGeoEclipticLongitude(double nValue) {
+		double Ec = (360.0 / Math.PI) * ECCENTRICITY_OF_ORBIT
+				* Math.sin(Math.toRadians(meanAnomaly));
+		double preliminaryLongitude = nValue + Ec
+				+ ECLIPTIC_LONGITUDE_AT_EPOCH_1990;
+		if (preliminaryLongitude > 360) {
+			preliminaryLongitude -= 360;
+		}
+		return preliminaryLongitude;
+	}
+
+	private double computeMeanAnomaly(double nValue) {
+		double someMean = nValue + ECLIPTIC_LONGITUDE_AT_EPOCH_1990
+				- ECLIPTIC_LONGITUDE_OF_PERIGREE;
+		return someMean < 0 ? someMean + 360 : someMean;
+	}
+
+	/**
+	 * TODO: implement this someday
+	 */
+	public RightAscension getRightAscension() {
+		return null;
+	}
+
+	/**
+	 * TODO: implement this someday
+	 */
+	public Declination getDeclination() {
+		return null;
+	}
+
+	public double getEclipticLongitude() {
+		return geoEclipticLongitude;
+	}
+
+	public double getMeanAnomaly() {
+		return meanAnomaly;
+	}
+
+}
+\ No newline at end of file