Added second attempt, which works apparently

.gitignore

@@ -3,4 +3,5 @@ target
 .idea
 data
 stars.svg
+stars2.svg
 *.log

src/main/java/SvgCreator.kt

@@ -7,6 +7,7 @@ import com.singulariti.os.ephemeris.domain.Star
 import com.singulariti.os.ephemeris.utils.StarCatalog
 import java.io.File
 import java.io.FileReader
+import java.io.PrintWriter
 import java.time.Duration
 import java.time.Instant
 import java.time.ZoneId
@@ -35,7 +36,7 @@ fun main(args: Array<String>) {
     val apparentMagnitudeCutOff = 7
 
     // make the svg file
-    File("stars.svg").printWriter().use { out ->
+    val block: (PrintWriter) -> Unit = { out ->
 
         out.println(""" <svg width="180" height="180">
                         <style>
@@ -54,7 +55,10 @@ fun main(args: Array<String>) {
 //            out.println("${it.key}, ${it.value}")
 //        }
         // second attempt
-        val calendarAstronomer = CalendarAstronomer(Date(Instant.parse("2018-10-05T10:15:30.00Z").toEpochMilli()))
+//        val calendarAstronomer = CalendarAstronomer(Date(Instant.parse("2018-10-05T10:15:30.00Z").toEpochMilli()))
+        val calendarAstronomer = CalendarAstronomer(51.02, 3.74)
+        val d = Date(Instant.parse("2018-10-05T10:15:30.00Z").toEpochMilli())
+        calendarAstronomer.date = d
 
         val colorIndices = HashSet<String>()
 
@@ -74,6 +78,8 @@ fun main(args: Array<String>) {
                     val convertDegreesToHoursMinutesSeconds = convertDecimalHoursToHMS(star.ra)
                     val convertDegreesToHoursMinutesSeconds1 = convertDecimalHoursToHMS(star.dec)
 
+                    calendarAstronomer
+
                     println("convertDegreesToHoursMinutesSeconds = ${convertDegreesToHoursMinutesSeconds} ${convertDegreesToHoursMinutesSeconds1}")
 
                     val star1 = Star(
@@ -115,6 +121,8 @@ fun main(args: Array<String>) {
                         var y = Math.sin(azimuth) * r
                         var x = Math.cos(azimuth) * r
 
+                        println("azimuth = ${azimuth} altitude = $altitude")
+
                         // shift everything +90 -> make sure the center of the circle is at (90,90)
                         y += 90
                         x += 90
@@ -176,6 +184,7 @@ fun main(args: Array<String>) {
 
         out.println("</svg>")
     }
+    File("stars.svg").printWriter().use(block)
 
 }
 

src/main/java/SvgCreator2.kt

@@ -0,0 +1,178 @@
+import java.io.File
+import java.io.PrintWriter
+import kotlin.math.acos
+import kotlin.math.asin
+import kotlin.math.cos
+import kotlin.math.sin
+
+
+/**
+ * http://jknight8.tripod.com/CelestialToAzEl.html#the%20source%20code
+ */
+fun main(args: Array<String>) {
+    // input
+    // julian day
+    val JD = 2458397
+    val LAT = 51.027930
+    val LON = 3.753585
+
+    // calculation
+    val D = JD - 2451545.0
+    val GMSThours = 18.697374558 + 24.06570982441908 * D
+    val GMST = (GMSThours % 24) * 15
+    val LMST = GMST + LON
+
+
+    // at least get this absolute magnitude (smaller is brighter) 6.5 = human vis
+    val apparentMagnitudeCutOff = 7
+
+
+    val block: (PrintWriter) -> Unit = { out ->
+        /**
+         *
+        .colorClassO5V { fill: #f0f8ff }
+        .colorClassB0V { fill: #f2f6ff }
+        .colorClassA0V { fill: #effbff }
+        .colorClassF0V { fill: #fffffb }
+        .colorClassG0V { fill: #ffffce }
+        .colorClassK0V { fill: #fff8a0 }
+        .colorClassM0V { fill: #fff8a0 }
+        .colorClassDefault { fill: white }
+
+
+        http://www.vendian.org/mncharity/dir3/starcolor/
+         */
+
+        out.println("""<svg width="180" height="180">
+                        <style>
+                            .properName { font: italic 1px sans-serif; stroke-width: 0.02px; stroke: black; }
+                            .constellationName { font: italic 0.2px sans-serif; stroke-width: 0.03px }
+                            .colorClassO5V { fill: #9bb0ff }
+                            .colorClassB0V { fill: #aabfff }
+                            .colorClassA0V { fill: #cad7ff }
+                            .colorClassF0V { fill: #f8f7ff }
+                            .colorClassG0V { fill: #fff4ea }
+                            .colorClassK0V { fill: #ffd2a1 }
+                            .colorClassM0V { fill: #ffcc6f }
+                            .colorClassDefault { fill: white }
+                        </style>
+                        <circle cx="90" cy="90" r="90" stroke="white" stroke-width="1" fill="black" />""".trimIndent())
+
+        // loop over stars
+        HygParser().parse().forEach { star ->
+            var RA = star.ra
+
+            // 26 % 24 = 2
+            // 2 % 24 = 2
+            // 27 % 24 = 3
+            // 102 % 10 = 2
+
+            RA = (RA % 24) * 15
+
+            var DEC = star.dec
+            // DEC is in range of -90 to 90... convert to 0 to 360
+            if (DEC < 0)
+                DEC += 360
+
+
+            // convert to az / alt
+            var HA = LMST - RA
+            if (HA < 0)
+                HA += 360
+
+            val sinALT = (sinDeg(DEC) * sinDeg(LAT)) + (cosDeg(DEC) * cosDeg(LAT) * cosDeg(HA))
+            val ALT = asinDeg(sinALT)
+            val cosA = (sinDeg(DEC) - sinDeg(ALT) * sinDeg(LAT)) / (cosDeg(ALT) * cosDeg(LAT))
+            val A = acosDeg(cosA)
+            val AZ =
+                    if (sinDeg(HA) < 0) {
+                        A
+                    } else {
+                        360 - A
+                    }
+
+            println("LAT = $LAT RA = $RA DEC = $DEC SINALT = $sinALT  ALT = $ALT HA = $HA AZ = $AZ")
+
+            if (ALT < 0) {
+                // do nothing... it's below to horizon
+            } else {
+                // altitude 0 means the outside of the circle... r is 90 then
+                val r = 90 - ALT
+                // draw the star! figure out an x,y coordinate on a circle
+                var y = sinDeg(AZ) * r
+                var x = cosDeg(AZ) * r
+
+
+                // shift everything +90 -> make sure the center of the circle is at (90,90)
+                y += 90
+                x += 90
+
+                // figure out the color
+                val colorClass = if (star.colorIndex.isNotEmpty()) {
+                    star.colorIndex.toDouble().let {
+                        when {
+                            it <= -.33 -> "colorClassO5V"
+                            it <= -.3 -> "colorClassB0V"
+                            it <= -0.02 -> "colorClassA0V"
+                            it <= 0.3 -> "colorClassF0V"
+                            it <= 0.58 -> "colorClassG0V"
+                            it <= 0.81 -> "colorClassK0V"
+                            it <= 1.40 -> "colorClassM0V"
+                            else -> "colorClassDefault"
+                        }
+                    }
+                } else {
+                    "colorClassDefault"
+                }
+
+                // determine the size of the circle -> depending on the apparent magnitude
+                val circleR = ((star.mag - apparentMagnitudeCutOff) * -1) * 0.05
+
+                // print name?
+                val nameOffset = 0.5
+                if (star.properName?.isNotEmpty() == true) {
+//                    out.println("""<text x="$x" y="$y" class="properName">${star.properName}</text>""")
+                    // write the text to the top right of the star
+                    out.println("""<text x="${x+nameOffset}" y="${y-nameOffset}" class="properName $colorClass">${star.properName}</text>""")
+                }
+
+                println("circleR = ${circleR}")
+
+                if(circleR>0) {
+                    out.println("""<circle cx="${x}" cy="${y}" r="$circleR" class="$colorClass"/>""")
+                }
+
+//                if (star.constellationAbbreviation?.isNotEmpty()) {
+//                    val col = when (star.constellationAbbreviation) {
+//                        "Dra" -> "red"
+//                        "UMa" -> "green"
+//                        "Her" -> "blue"
+//                        else -> "white"
+//                    }
+//                    out.println("""<text x="$x" y="$y" class="constellationName" fill="$col" stroke="$col">${star.constellationAbbreviation}</text>""")
+//                }
+            }
+        }
+
+        out.println("</svg>")
+    }
+
+    File("stars2.svg").printWriter().use(block)
+
+}
+
+fun sinDeg(degrees: Double): Double {
+    return sin(Math.toRadians(degrees))
+}
+
+fun cosDeg(degrees: Double): Double {
+    return cos(Math.toRadians(degrees))
+}
+
+fun asinDeg(sin: Double): Double {
+    return Math.toDegrees(asin(sin))
+}
+
+fun acosDeg(cos: Double): Double {
+    return Math.toDegrees(acos(cos))
+}