From 9f02eb2d0f324757fdd3a47c1a92864976bb1202 Mon Sep 17 00:00:00 2001
From: "Michael J. Roberts" <michael@observerly.com>
Date: Fri, 3 May 2024 10:36:10 +0100
Subject: [PATCH] feat: add GetEquatorialCoordinate(datetime time.Time) to
 coordinates module in @observerly/sidera.

feat: add GetEquatorialCoordinate(datetime time.Time) to coordinates module in @observerly/sidera.
---
 pkg/solar/sun.go      | 20 ++++++++++++++++++++
 pkg/solar/sun_test.go | 19 +++++++++++++++++++
 2 files changed, 39 insertions(+)

diff --git a/pkg/solar/sun.go b/pkg/solar/sun.go
index 4fd5cfa..7e4bfa5 100644
--- a/pkg/solar/sun.go
+++ b/pkg/solar/sun.go
@@ -15,6 +15,7 @@ import (
 	"time"
 
 	"github.com/observerly/sidera/pkg/common"
+	"github.com/observerly/sidera/pkg/coordinates"
 	"github.com/observerly/sidera/pkg/epoch"
 )
 
@@ -130,3 +131,22 @@ func GetEclipticCoordinate(datetime time.Time) common.EclipticCoordinate {
 }
 
 /*****************************************************************************************************************/
+
+/*
+the Equatorial Coordinate of the Sun for a given datetime
+
+The Solar Equatorial Coordinate is the position of the Sun in the sky relative to the celestial equator.
+
+The Solar Equatorial Coordinate is an important concept in solar astronomy, as it is used to calculate the position
+of the Sun in the sky at any given time. By knowing the Solar Equatorial Coordinate, an observer can determine the
+Sun's position relative to the vernal equinox and calculate the time of sunrise, sunset, and other solar events.
+*/
+func GetEquatorialCoordinate(datetime time.Time) common.EquatorialCoordinate {
+	// get the solar ecliptic coordinate:
+	ecliptic := GetEclipticCoordinate(datetime)
+
+	// convert the solar ecliptic coordinate to the solar equatorial coordinate:
+	return coordinates.ConvertEclipticToEquatorialCoordinate(datetime, ecliptic)
+}
+
+/*****************************************************************************************************************/
diff --git a/pkg/solar/sun_test.go b/pkg/solar/sun_test.go
index 3869d5b..55234a9 100644
--- a/pkg/solar/sun_test.go
+++ b/pkg/solar/sun_test.go
@@ -75,3 +75,22 @@ func TestGetSolarEclipticCoordinate(t *testing.T) {
 }
 
 /*****************************************************************************************************************/
+
+func TestSolarEquatorialCoordinate(t *testing.T) {
+	var got = GetEquatorialCoordinate(datetime)
+
+	var want = common.EquatorialCoordinate{
+		RightAscension: 51.96564888161902,
+		Declination:    18.256452,
+	}
+
+	if got.RightAscension-want.RightAscension > 0.0001 {
+		t.Errorf("got %f, wanted %f", got.RightAscension, want.RightAscension)
+	}
+
+	if got.Declination-want.Declination > 0.0001 {
+		t.Errorf("got %f, wanted %f", got.Declination, want.Declination)
+	}
+}
+
+/*****************************************************************************************************************/