moon visibility for start and end

CHANGELOG.md

@@ -23,3 +23,6 @@ All notable changes to this project will be documented in this file.
 
 - Renamed to "pray-calc" and removed old package
 - Improved Synodic accuracy slightly and lastKnownMoon
+
+## [1.4.1] = 2013-12-01
+- Modified getMoonVisibility to use adjusted moon phase for end of cycle

getMoonVisibility.js

@@ -12,7 +12,7 @@
  * @returns {Object} An object containing moon details: phase, position, illumination, and visibility.
  */
 
-function getMoonVisibility(phase, position, illumination, elevation = 50, temp = 15, pressure = 1013.25, humidity = 50, clouds = 0) {
+function getMoonVisibility(phase, position = 0, illumination = 0, elevation = 50, temp = 15, pressure = 1013.25, humidity = 50, clouds = 0) {
     
     /** Placeholder Simplified Algorithm...
      * This is a very simplified algorithm that is not intended to be precise or accurate.
@@ -20,20 +20,37 @@ function getMoonVisibility(phase, position, illumination, elevation = 50, temp =
      * Using a window of earliest general visibility until near definite visibility is reached.
      */
     
+    // Convert Phase from 0-1 to be 0 (full moon) to 0.5 (new moon) scale
+    const aphase = (phase - 0.5) < 0 ? -(phase - 0.5) : (phase - 0.5);
+
+    // Get synodic month and phase hour for adjustic moon phase
     const sMonth = 29.530588861;
-    const phaseHour = 1 / 24 / sMonth; // ~ 0.001410966333
-    const startVis = phaseHour * 15;   // ~ 0.02116449584
-    const endofVis = phaseHour * 30;   // ~ 0.04232899168
-    const visWindow = endofVis - startVis;
+    const phaseHour = 1 / 24 / sMonth;  // ~ 0.001410966333
+    const ahour = phaseHour / 2;        // ~ 0.0007054831663
+
+    // Get estimated visibility window of a new moon (and ending)
+    const v1 = ahour * 15;               // ~ 0.01058224749
+    const v2 = ahour * 30;               // ~ 0.02116449499
+    const w1 = 0.5 - v1;                 // ~ 0.48941775251
+    const w2 = 0.5 - v2;                 // ~ 0.47883550501
+    const win = w1 - w2;                 // ~ 0.01058224749
 
     let visibility = 0;
-    if (phase > endofVis) {
+    if (aphase < w2) {
         visibility = 1;
-    } else if (phase > startVis) {
-        visibility = (phase - startVis) / visWindow;
+    } else if (aphase < w1) {
+        visibility = (w1 - aphase) / win;
     }
 
     return visibility;
 }
 
 module.exports = { getMoonVisibility };
+
+/* console.log(getMoonVisibility(0.010));
+console.log(getMoonVisibility(0.012));
+console.log(getMoonVisibility(0.014));
+console.log(getMoonVisibility(0.016));
+console.log(getMoonVisibility(0.018));
+console.log(getMoonVisibility(0.020));
+console.log(getMoonVisibility(0.022)); */

package.json

@@ -1,6 +1,6 @@
 {
   "name": "pray-calc",
-  "version": "1.4.0",
+  "version": "1.4.1",
   "description": "Prayer times calculator using nrel-spa and custom formula for Fajr and Isha angles (as well as traditional static angle methods in the All function)",
   "main": "index.js",
   "scripts": {