Added MoonPhase library

src/MoonPhase.cpp

@@ -0,0 +1,96 @@
+// Calculate the phase and position of the moon for a given date.
+// The algorithm is simple and adequate for many purposes.
+//
+// This software was originally adapted to javascript by Stephen R. Schmitt
+// from a BASIC program from the 'Astronomical Computing' column of Sky & Telescope,
+// April 1994, page 86, written by Bradley E. Schaefer.
+//
+// Subsequently adapted from Stephen R. Schmitt's javascript to c++ for the Arduino
+// by Cyrus Rahman, this work is subject to Stephen Schmitt's copyright:
+//
+// Copyright 2004 Stephen R. Schmitt
+// You may use or modify this source code in any way you find useful, provided
+// that you agree that the author(s) have no warranty, obligations or liability.  You
+// must determine the suitability of this source code for your use.
+
+#include <math.h>
+#include "MoonPhase.h"
+
+// Names of lunar phases
+static const char *phaseNames[] = {"New", "Evening Crescent", "First Quarter",
+				   "Waxing Gibbous", "Full", "Waning Gibbous",
+				   "Last Quarter", "Morning Crescent"};
+// Names of Zodiac constellations
+static const char *zodiacNames[] = {"Pisces", "Aries", "Taurus", "Gemini", "Cancer",
+				    "Leo", "Virgo", "Libra", "Scorpio", "Sagittarius",
+				    "Capricorn", "Aquarius"};
+// Ecliptic angles of Zodiac constellations
+static const float zodiacAngles[] = {33.18, 51.16, 93.44, 119.48, 135.30, 173.34,
+				     224.17, 242.57, 271.26, 302.49, 311.72, 348.58};
+
+// Constructor initialization.
+MoonPhase::MoonPhase() {
+  jDate = 0;
+  phase = 0;
+  age = 0;
+  fraction = 0;
+  distance = 0;
+  latitude = 0;
+  longitude = 0;
+  phaseName = zodiacName = "";
+}
+
+// Determine the Moon Phase and orbital positions for the specified time.
+void
+MoonPhase::calculate(time_t t) {
+  jDate = julianDate(t);
+
+  // Calculate illumination (synodic) phase.
+  // From number of days since new moon on Julian date MOON_SYNODIC_OFFSET
+  // (1815UTC January 6, 2000), determine remainder of incomplete cycle.
+  phase = (jDate - MOON_SYNODIC_OFFSET) / MOON_SYNODIC_PERIOD;
+  phase -= floor(phase);
+
+  // Calculate age and illumination fraction.
+  age = phase * MOON_SYNODIC_PERIOD;
+  fraction = (1.0 - cos(2 * M_PI * phase)) * 0.5;
+  phaseName = phaseNames[(int)(phase * 8 + 0.5) % 8];
+
+  // Calculate distance from anomalistic phase.
+  double distancePhase = (jDate - MOON_DISTANCE_OFFSET) / MOON_DISTANCE_PERIOD;
+  distancePhase -= floor(distancePhase);
+  distance = 60.4 - 3.3 * cos(2 * M_PI * distancePhase)
+		  - 0.6 * cos(2 * 2 * M_PI * phase - 2 * M_PI * distancePhase)
+		  - 0.5 * cos(2 * 2 * M_PI * phase);
+
+  // Calculate ecliptic latitude from nodal (draconic) phase.
+  double latPhase = (jDate - MOON_LATITUDE_OFFSET) / MOON_LATITUDE_PERIOD;
+  latPhase -= floor(latPhase);
+  latitude = 5.1 * sin(2 * M_PI * latPhase);
+
+  // Calculate ecliptic longitude from sidereal motion.
+  double longPhase = (jDate - MOON_LONGITUDE_OFFSET) / MOON_LONGITUDE_PERIOD;
+  longPhase -= floor(longPhase);
+  longitude = 360 * longPhase
+	      + 6.3 * sin(2 * M_PI * distancePhase)
+	      + 1.3 * sin(2 * 2 * M_PI * phase - 2 * M_PI * distancePhase)
+	      + 0.7 * sin(2 * 2 * M_PI * phase);
+  if (longitude > 360)
+    longitude -= 360;
+
+  // Select the Zodiac name.
+  zodiacName = zodiacNames[0];
+  for (int i = 0; i < sizeof(zodiacAngles) / sizeof(float); i++) {
+    if (longitude < zodiacAngles[i]) {
+      zodiacName = zodiacNames[i];
+      break;
+    }
+  }
+}
+
+// Determine Julian date from Unix time.
+// Provides marginally accurate results with older Arduino 4-byte double.
+double
+MoonPhase::julianDate(time_t t) {
+  return (t / 86400.0L + 2440587.5);
+}

src/MoonPhase.h

@@ -0,0 +1,33 @@
+#ifndef MoonPhase_h
+#define MoonPhase_h
+
+#include <time.h>
+
+#define MOON_SYNODIC_PERIOD   29.530588853   // Period of moon cycle in days.
+#define	MOON_SYNODIC_OFFSET   2451550.26     // Reference cycle offset in days.
+#define MOON_DISTANCE_PERIOD  27.55454988    // Period of distance oscillation
+#define MOON_DISTANCE_OFFSET  2451562.2
+#define MOON_LATITUDE_PERIOD  27.212220817   // Latitude oscillation
+#define	MOON_LATITUDE_OFFSET  2451565.2
+#define MOON_LONGITUDE_PERIOD 27.321582241   // Longitude oscillation
+#define	MOON_LONGITUDE_OFFSET 2451555.8
+
+class MoonPhase {
+  public:
+    double jDate;
+    double phase;	      // 0 - 1, 0.5 = full
+    double age;		      // Age in days of current cycle
+    double fraction;	      // Fraction of illuminated disk
+    double distance;	      // Moon distance in earth radii
+    double latitude;	      // Moon ecliptic latitude
+    double longitude;	      // Moon ecliptic longitude
+    const char *phaseName;    // New, Full, etc.
+    const char *zodiacName;   // Constellation 
+
+    MoonPhase();
+    void calculate(time_t);
+
+  private:
+    double julianDate(time_t);
+};
+#endif