public static void TangentToCelestial(double X, double Y, double ra0Deg, double de0Deg, out double raDeg, out double deDeg)
{
double ra0 = ra0Deg * Math.PI / 180;
double de0 = de0Deg * Math.PI / 180;
double ra = ra0 + Math.Atan(-X / (Math.Cos(de0) - Y * Math.Sin(de0)));
double de = Math.Asin((Math.Sin(de0) + Y * Math.Cos(de0)) / Math.Sqrt(1 + X * X + Y * Y));
deDeg = de * 180 / Math.PI;
ra = AngleUtility.Range(ra, 2 * Math.PI);
raDeg = ra * 180 / Math.PI;
}
internal static List <SearchZone> GetZones(double raDeg, double deDeg, double radiusDeg)
{
raDeg = AngleUtility.Range(raDeg, 360);
List <SearchZone> zones = new List <SearchZone>();
double deFrom = deDeg - radiusDeg / 2.0;
double deTo = deDeg + radiusDeg / 2.0;;
if (deFrom < -90)
{
deTo = deDeg + Math.Max(Math.Abs(deFrom + 90), radiusDeg / 2.0);
deFrom = -90;
}
else if (deTo > 90)
{
deFrom = 90 - Math.Max(Math.Abs(deTo - 90), radiusDeg / 2.0);
deTo = 90;
}
double aspect = Math.Cos(Math.Max(Math.Abs(deFrom), Math.Abs(deTo)) * Math.PI / 180);
double raFrom = raDeg - (radiusDeg / (2.0 * aspect));
double raTo = raDeg + (radiusDeg / (2.0 * aspect));
if (raTo - raFrom > 360)
{
raFrom = 0;
raTo = 360;
}
if (raFrom < 0)
{
// 2 zones: raFrom..360; 0..raTo
raFrom = AngleUtility.Range(raFrom, 360);
zones.Add(new SearchZone {
RAFrom = raFrom, RATo = 360, DEFrom = deFrom, DETo = deTo
});
zones.Add(new SearchZone {
RAFrom = 0, RATo = raTo, DEFrom = deFrom, DETo = deTo
});
}
else if (raTo > 360)
{
// 2 zones: raFrom..360; 0..raTo
raTo = AngleUtility.Range(raTo, 360);
zones.Add(new SearchZone {
RAFrom = raFrom, RATo = 360, DEFrom = deFrom, DETo = deTo
});
zones.Add(new SearchZone {
RAFrom = 0, RATo = raTo, DEFrom = deFrom, DETo = deTo
});
}
else
{
zones.Add(new SearchZone {
RAFrom = raFrom, RATo = raTo, DEFrom = deFrom, DETo = deTo
});
}
return(zones);
}