├── .gitattributes ├── .gitignore ├── stcalc.sln └── stcalc ├── Moment.cs ├── Program.cs ├── Properties └── launchSettings.json ├── RightAscension.cs └── stcalc.csproj /.gitattributes: -------------------------------------------------------------------------------- 1 | ############################################################################### 2 | # Set default behavior to automatically normalize line endings. 3 | ############################################################################### 4 | * text=auto 5 | 6 | ############################################################################### 7 | # Set default behavior for command prompt diff. 8 | # 9 | # This is need for earlier builds of msysgit that does not have it on by 10 | # default for csharp files. 11 | # Note: This is only used by command line 12 | ############################################################################### 13 | #*.cs diff=csharp 14 | 15 | ############################################################################### 16 | # Set the merge driver for project and solution files 17 | # 18 | # Merging from the command prompt will add diff markers to the files if there 19 | # are conflicts (Merging from VS is not affected by the settings below, in VS 20 | # the diff markers are never inserted). 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2 | 3 | namespace stcalc 4 | { 5 | /// 6 | /// A moment is a specific point in time down to the optional millisecond. 7 | /// 8 | public struct Moment 9 | { 10 | public int Year { get; } 11 | public int Month { get; } 12 | public int Day { get; } 13 | public int Hour { get; } 14 | public int Minute { get; } 15 | public int Second { get; } 16 | public int Millisecond { get; } 17 | 18 | public Moment(DateTime dt) 19 | { 20 | Year = dt.Year; 21 | Month = dt.Month; 22 | Day = dt.Day; 23 | Hour = dt.Hour; 24 | Minute = dt.Minute; 25 | Second = dt.Second; 26 | Millisecond = dt.Millisecond; 27 | } 28 | 29 | /// 30 | /// Creates a Moment with known values down to the millisecond. 31 | /// 32 | /// 33 | /// 34 | /// 35 | /// 36 | /// 37 | /// 38 | /// 39 | public Moment(int year, int month, int day, int hour, int minute, int second = 0, int millisecond = 0) 40 | { 41 | Year = year; 42 | Month = month; 43 | Day = day; 44 | Hour = hour; 45 | Minute = minute; 46 | Second = second; 47 | Millisecond = millisecond; 48 | } 49 | 50 | /// 51 | /// Creates a Moment with known values using a fraction to represent the day 52 | /// of the month as well as the hour, minute, second, and millisecond component. 53 | /// For example, 4.812 is the 4th day at 19:29 (7:29 PM). 54 | /// 55 | /// 56 | /// 57 | /// 58 | public Moment(int year, int month, double day) 59 | { 60 | if (double.IsNaN(day)) 61 | { 62 | throw new ArgumentException("day must be a valid value."); 63 | } 64 | 65 | Year = year; 66 | Month = month; 67 | 68 | // leverage the C# TimeSpan struct 69 | var ts = TimeSpan.FromDays(day); 70 | Day = ts.Days; 71 | Hour = ts.Hours; 72 | Minute = ts.Minutes; 73 | Second = ts.Seconds; 74 | Millisecond = ts.Milliseconds; 75 | } 76 | 77 | /// 78 | /// Creates a Moment with a known Julian Day (JD) value. 79 | /// 80 | /// 81 | public Moment(double julianDay) 82 | { 83 | if (double.IsNaN(julianDay)) 84 | { 85 | throw new ArgumentException("julianDay must be a valid value."); 86 | } 87 | 88 | double A; 89 | double B; 90 | int C; 91 | double D; 92 | int E; 93 | double jd = julianDay + 0.5; 94 | double Z = Math.Truncate(jd); 95 | double F = jd - Math.Truncate(jd); 96 | 97 | if (Z < 2299161) 98 | { 99 | A = Z; 100 | } 101 | else 102 | { 103 | var a = (int)((Z - 1867216.25) / 36524.25); 104 | A = Z + 1 + a - (int)(a / 4); 105 | } 106 | 107 | B = A + 1524; 108 | C = (int)((B - 122.1) / 365.25); 109 | D = (int)(365.25 * C); 110 | E = (int)((B - D) / 30.6001); 111 | 112 | int Y; 113 | int M; 114 | double day = B - D - (int)(30.6001 * E) + F; 115 | switch (E) 116 | { 117 | case 14: 118 | case 15: 119 | M = E - 13; 120 | break; 121 | 122 | default: 123 | M = E - 1; 124 | break; 125 | } 126 | 127 | switch (M) 128 | { 129 | case 1: 130 | case 2: 131 | Y = C - 4715; 132 | break; 133 | 134 | default: 135 | Y = C - 4715; 136 | break; 137 | } 138 | 139 | Year = Y; 140 | Month = M; 141 | 142 | // leverage the C# TimeSpan struct 143 | var ts = TimeSpan.FromDays(day); 144 | Day = ts.Days; 145 | Hour = ts.Hours; 146 | Minute = ts.Minutes; 147 | Second = ts.Seconds; 148 | Millisecond = ts.Milliseconds; 149 | } 150 | 151 | public double DayOfMonth 152 | { 153 | get 154 | { 155 | return Day + (Hour / 24.0) + (Minute / 1440.0) + (Second + Millisecond / 1000.0) / 86400.0; 156 | } 157 | } 158 | 159 | /// 160 | /// A Julian Day (JD) is a continuous count of days and fractions thereof 161 | /// starting at 1 Jan -4712 at noon UTC to a given point in time thereafter. 162 | /// 163 | public double JulianDay 164 | { 165 | get 166 | { 167 | int Y = Year; 168 | int M = Month; 169 | double B = 0; // Julian calendar default 170 | 171 | // if the date is Jan or Feb then it is considered to be in the 172 | // 13th or 14th month of the preceding year. 173 | switch (M) 174 | { 175 | case 1: 176 | case 2: 177 | Y -= 1; 178 | M += 12; 179 | break; 180 | 181 | default: 182 | break; 183 | } 184 | 185 | if (!IsJulianDate()) // convert to Gregorian calendar 186 | { 187 | double A = Math.Floor(Y / 100.0); 188 | B = 2 - A + Math.Floor(A / 4); 189 | } 190 | 191 | return Math.Floor(365.25 * (Y + 4716)) + Math.Floor(30.6001 * (M + 1)) + DayOfMonth + B - 1524.5; 192 | } 193 | } 194 | 195 | public double JD 196 | { 197 | get 198 | { 199 | return JulianDay; 200 | } 201 | } 202 | 203 | public double JDE 204 | { 205 | get 206 | { 207 | return JulianDay; 208 | } 209 | } 210 | 211 | /// 212 | /// Time T is measured in Julian centuries of 36525 ephemeris days from the epoch J2000.0 213 | /// 214 | public double TimeT 215 | { 216 | get 217 | { 218 | return (JulianDay - 2451545.0) / 36525; 219 | } 220 | } 221 | 222 | /// 223 | /// Day D is the number of days (and decimals thereof) from the epoch J2000.0 224 | /// 225 | public double DayD 226 | { 227 | get 228 | { 229 | return JulianDay - 2451545.0; 230 | } 231 | } 232 | 233 | /// 234 | /// Pope Gregory introduced the Gregorian calendar in October 1582 when the 235 | /// calendar had drifted 10 days. Dates prior to 4 Oct 1582 are Julian dates 236 | /// and dates after 15 Oct 1582 are Gregorian dates. Any date in the gap is 237 | /// invalid on the Gregorian calendar. 238 | /// 239 | /// 240 | public bool IsJulianDate() 241 | { 242 | if (Year > 1582) 243 | return false; 244 | 245 | if (Year < 1582) 246 | return true; 247 | 248 | // year is 1582 so check month 249 | if (Month > 10) 250 | return false; 251 | 252 | if (Month < 10) 253 | return true; 254 | 255 | // month is 10 so check days 256 | if (Day > 14) 257 | return false; 258 | 259 | return true; 260 | } 261 | 262 | public bool IsGregorianDate() 263 | { 264 | if (Year > 1582) 265 | return true; 266 | 267 | if (Year < 1582) 268 | return false; 269 | 270 | // year is 1582 so check month 271 | if (Month > 10) 272 | return true; 273 | 274 | if (Month < 10) 275 | return false; 276 | 277 | // month is 10 so check days 278 | if (Day > 5) 279 | return true; 280 | 281 | return false; 282 | } 283 | 284 | public override bool Equals(object obj) 285 | { 286 | if (!(obj is Moment)) 287 | return false; 288 | 289 | Moment moment = (Moment)obj; 290 | return moment.JulianDay == this.JulianDay; 291 | } 292 | 293 | public override string ToString() 294 | { 295 | DateTime dt = new DateTime(Year, Month, Day, Hour, Minute, Second, DateTimeKind.Utc); 296 | return dt.ToString("u"); 297 | } 298 | 299 | public static bool operator ==(Moment m1, Moment m2) 300 | { 301 | return m1.JulianDay == m2.JulianDay; 302 | } 303 | 304 | public static bool operator !=(Moment m1, Moment m2) 305 | { 306 | return m1.JulianDay != m2.JulianDay; 307 | } 308 | 309 | public override int GetHashCode() 310 | { 311 | return base.GetHashCode(); 312 | } 313 | } 314 | } 315 | -------------------------------------------------------------------------------- /stcalc/Program.cs: -------------------------------------------------------------------------------- 1 | using System; 2 | using System.Globalization; 3 | 4 | namespace stcalc 5 | { 6 | public class Program 7 | { 8 | private const string _usage = "Enter your longitude and (optionally) local date and time. Usage: stcalc -122.675 2020-03-03 13:00"; 9 | static void Main(string[] args) 10 | { 11 | // Test if input arguments were supplied. 12 | if (args.Length < 1) 13 | { 14 | Console.WriteLine("Please enter your longitude. If you leave date and time blank the current moment is used."); 15 | Console.WriteLine(_usage); 16 | return; 17 | } 18 | 19 | if (!IsValidLongitude(args[0], out double longitude)) 20 | { 21 | Console.WriteLine("Please enter a valid longitude between -180 and 180."); 22 | Console.WriteLine(_usage); 23 | return; 24 | } 25 | 26 | var dateValue = (args.Length > 1) ? args[1] : string.Empty; 27 | if (!IsValidDate(dateValue, out DateTime d)) 28 | { 29 | Console.WriteLine("Please enter a valid date in the format YYYY-MM-DD"); 30 | Console.WriteLine(_usage); 31 | return; 32 | } 33 | 34 | var timeValue = (args.Length > 2) ? args[2] : string.Empty; 35 | if (!IsValidTime(timeValue, out TimeSpan ts)) 36 | { 37 | Console.WriteLine("Please enter a valid time in the format HH:MM"); 38 | Console.WriteLine(_usage); 39 | return; 40 | } 41 | 42 | DateTime localDateTime = d + ts; 43 | DateTime utcDateTime = TimeZoneInfo.ConvertTimeToUtc(localDateTime, TimeZoneInfo.Local); 44 | 45 | // lines 55 thru 59 are from Meeus, Chap 12 (pp 87-89) 46 | var moment = new Moment(utcDateTime); 47 | var JD = moment.JulianDay; 48 | var T = ((JD - 2451545.0) / 36525); 49 | var theta0 = 280.46061837 + 360.98564736629 * (JD - 2451545.0) + (0.000387933 * T * T) - (T * T * T / 38710000.0); // (12.4) 50 | var gmstRA = new RightAscension(ReduceAngle(theta0)); 51 | 52 | /* 53 | From Textbook on Spherical Astronomy, 6th Ed. by W.M. Smart (p. 41): 54 | 55 | Sidereal time at Greenwich = GST + longitude l of your location east or west of Greenwich. 56 | In Portland, Oregon (-122.67) this results in a subtraction from GST. The result is then 57 | converted into hours, minutes, and seconds via 15 deg = 1h, 15' = 1m, and 15'' = 1s. This 58 | is the local sidereal time (LST). 59 | */ 60 | 61 | var lmstRA = new RightAscension(gmstRA.ToDecimalDegrees() + longitude); 62 | 63 | Console.WriteLine("Longitude: " + longitude); 64 | Console.WriteLine("Local DateTime: " + localDateTime.ToString()); 65 | Console.WriteLine("UTC DateTime: " + utcDateTime.ToString()); 66 | Console.WriteLine(Environment.NewLine); 67 | 68 | Console.WriteLine("JD: " + JD); 69 | Console.WriteLine("T: " + T); 70 | Console.WriteLine("theta0 from Meeus formula (12.4): " + theta0); 71 | Console.WriteLine(Environment.NewLine); 72 | 73 | Console.WriteLine("Greenwich Mean Sidereal Time (dec deg): " + ReduceAngle(theta0)); 74 | Console.WriteLine("Greenwich Mean Sidereal Time (HMS): " + gmstRA.ToString()); 75 | Console.WriteLine("Local Mean Sidereal Time (dec deg): " + lmstRA.ToDecimalDegrees()); 76 | Console.WriteLine("Local Mean Sidereal Time (HMS): " + lmstRA.ToString()); 77 | Console.WriteLine(Environment.NewLine); 78 | 79 | Console.WriteLine("Press ENTER to exit."); 80 | Console.ReadLine(); 81 | } 82 | 83 | private static bool IsValidLongitude(string value, out double d) 84 | { 85 | bool test = double.TryParse(value, out d); 86 | if (!test) 87 | { 88 | return false; 89 | } 90 | 91 | return (d >= -180 && d <= 180); 92 | } 93 | 94 | private static bool IsValidDate(string value, out DateTime d) 95 | { 96 | if (string.IsNullOrEmpty(value)) 97 | { 98 | d = DateTime.Today; 99 | return false; 100 | } 101 | 102 | string pattern = "yyyy-MM-dd"; 103 | CultureInfo ci = CultureInfo.InvariantCulture; 104 | DateTimeStyles dts = DateTimeStyles.None; 105 | try 106 | { 107 | return DateTime.TryParseExact(value, pattern, ci, dts, out d); 108 | } 109 | catch 110 | { 111 | Console.WriteLine("Invalid date or not in format YYYY-MM-DD."); 112 | d = DateTime.Today; 113 | return false; 114 | } 115 | } 116 | 117 | private static bool IsValidTime(string value, out TimeSpan ts) 118 | { 119 | if (string.IsNullOrEmpty(value)) 120 | { 121 | ts = DateTime.Now.TimeOfDay; 122 | return false; 123 | } 124 | 125 | try 126 | { 127 | return TimeSpan.TryParse(value, out ts); 128 | } 129 | catch 130 | { 131 | Console.WriteLine("Invalid time or not in format HH:MM."); 132 | ts = DateTime.Now.TimeOfDay; 133 | return false; 134 | } 135 | } 136 | 137 | /// 138 | /// For very large angles reduce to put in interval between 0 and 360 139 | /// 140 | /// 141 | /// 142 | private static double ReduceAngle(double d) 143 | { 144 | d %= 360; 145 | if (d < 0) 146 | { 147 | d += 360; 148 | } 149 | 150 | return d; 151 | } 152 | } 153 | } 154 | -------------------------------------------------------------------------------- /stcalc/Properties/launchSettings.json: -------------------------------------------------------------------------------- 1 | { 2 | "profiles": { 3 | "stcalc": { 4 | "commandName": "Project", 5 | "commandLineArgs": "-122.67563 2020-03-19 20:50" 6 | } 7 | } 8 | } -------------------------------------------------------------------------------- /stcalc/RightAscension.cs: -------------------------------------------------------------------------------- 1 | using System; 2 | 3 | namespace stcalc 4 | { 5 | public struct RightAscension 6 | { 7 | public RightAscension(double hours, double minutes, double seconds) 8 | { 9 | if (hours < 0 || hours > 23) 10 | { 11 | throw new ArgumentException("Hours must be between 0 and 23", "hours"); 12 | } 13 | 14 | if (minutes < 0 || minutes > 59) 15 | { 16 | throw new ArgumentException("Minutes must be between 0 and 59", "minutes"); 17 | } 18 | 19 | if (seconds < 0 || seconds > 59) 20 | { 21 | throw new ArgumentException("Seconds must be between 0 and 59", "seconds"); 22 | } 23 | 24 | Hours = hours; 25 | Minutes = minutes; 26 | Seconds = seconds; 27 | } 28 | 29 | public RightAscension(double decimalDegrees) 30 | { 31 | Hours = ToHours(decimalDegrees); 32 | Minutes = ToMinutes(decimalDegrees); 33 | Seconds = ToSeconds(decimalDegrees); 34 | } 35 | 36 | public double Hours { get; } 37 | public double Minutes { get; } 38 | public double Seconds { get; } 39 | 40 | public double ToDecimalDegrees() => (Hours + (Minutes / 60) + (Seconds / 3600)) * 15; 41 | public override string ToString() 42 | { 43 | var d = ToDecimalDegrees(); 44 | var h = (int)d / 15; 45 | var m = (int)(((d / 15) - h) * 60); 46 | var s = ((((d / 15) - h) * 60) - m) * 60; 47 | var ss = Math.Round(s); 48 | return $"{h}h {m}m {ss}s"; 49 | } 50 | 51 | private static double ToHours(double d) 52 | { 53 | return d / 15; 54 | } 55 | 56 | private static double ToMinutes(double d) 57 | { 58 | var h = ToHours(d); 59 | return ((d / 15) - h) * 60; 60 | } 61 | 62 | private static double ToSeconds(double d) 63 | { 64 | var h = ToHours(d); 65 | var m = ToMinutes(d); 66 | return ((((d / 15) - h) * 60) - m) * 60; 67 | } 68 | } 69 | } 70 | -------------------------------------------------------------------------------- /stcalc/stcalc.csproj: -------------------------------------------------------------------------------- 1 |  2 | 3 | 4 | Exe 5 | netcoreapp3.1 6 | 7 | 8 | 9 | --------------------------------------------------------------------------------