fix: calculation of apparent sidereal time at Greenwich

Fixes #40
klausbrunner · Dec 1, 2023 · e79ecf1 · e79ecf1
1 parent 4375cfe
commit e79ecf1
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diff --git a/src/main/java/net/e175/klaus/solarpositioning/SPA.java b/src/main/java/net/e175/klaus/solarpositioning/SPA.java
@@ -571,8 +571,8 @@ private static double calculateApparentSiderealTimeAtGreenwich(
         limitDegreesTo360(
             280.46061837
                 + 360.98564736629 * (jd.julianDate() - 2451545)
-                + 0.000387933 * pow(jd.julianCentury(), 2)
-                - pow(jd.julianCentury(), 2) / 38710000);
+                + pow(jd.julianCentury(), 2) * (0.000387933 - jd.julianCentury() / 38710000));
+
     return nu0degrees + deltaPsi * cos(toRadians(epsilonDegrees));
   }
 

diff --git a/src/test/java/net/e175/klaus/solarpositioning/test/SPATest.java b/src/test/java/net/e175/klaus/solarpositioning/test/SPATest.java
@@ -22,8 +22,8 @@ void testSpaExample() {
     SolarPosition result =
         SPA.calculateSolarPosition(time, 39.742476, -105.1786, 1830.14, 67, 820, 11);
 
-    assertEquals(194.340241, result.azimuth(), TOLERANCE / 10);
-    assertEquals(50.111622, result.zenithAngle(), TOLERANCE / 10);
+    assertEquals(194.340241, result.azimuth(), TOLERANCE / 100);
+    assertEquals(50.111622, result.zenithAngle(), TOLERANCE / 100);
   }
 
   @Test