public void Horizontal2EquatorialTest(double azimuth, double altitude, double latitude, double expectedX, double expectedY)
{
AAS2DCoordinate horizontal = AASCoordinateTransformation.Horizontal2Equatorial(azimuth, altitude, latitude);
Assert.Equal(expectedX, horizontal.X);
Assert.Equal(expectedY, horizontal.Y);
}
public Coordinate OrientationToCoordinate(Orientation currHorizontal, DateTime datetime)
{
// We don't want to modify the current orientation, so we must create a new instance
Orientation horizontal = (Orientation)currHorizontal.Clone();
if (horizontal == null)
{
throw new ArgumentException("Orientation cannot be null");
}
// Since AASharp considers south zero, flip the orientation 180 degrees
horizontal.Azimuth += 180;
if (horizontal.Azimuth > 360)
{
horizontal.Azimuth -= 360;
}
AAS2DCoordinate equatorial = AASCoordinateTransformation.Horizontal2Equatorial(horizontal.Azimuth, horizontal.Elevation, Location.Latitude);
AASDate date = new AASDate(datetime.Year, datetime.Month, datetime.Day, datetime.Hour, datetime.Minute, datetime.Second, true);
double ApparentGreenwichSiderealTime = AASSidereal.ApparentGreenwichSiderealTime(date.Julian);
double LongtitudeAsHourAngle = AASCoordinateTransformation.DegreesToHours(Location.Longitude);
double RightAscension = ApparentGreenwichSiderealTime - LongtitudeAsHourAngle - equatorial.X;
if (RightAscension < 0)
{
RightAscension += 24;
}
return(new Coordinate(RightAscension, equatorial.Y));
}
public EquatorialCoords Horizontal2Equatorial(double azimuth, double altitude){
AAS2DCoordinate coords = AASCoordinateTransformation.Horizontal2Equatorial (azimuth+180, altitude, location.latitude);
//right ascension (alpha) = apparent sidereal time at Greenwich (theta) - Local hour angle (H) - observer's longitude (L, positive west, negative east from Greenwich)
double theta0Apparent = AASSidereal.ApparentGreenwichSiderealTime (jd);
double ra = theta0Apparent - coords.X - location.longitude / 15d;
return new EquatorialCoords(new HourAngle(ra), new DegreesAngle( coords.Y ));
}
// converts horizontal coordinates to equitorial coordinates
public static AAS2DCoordinate ToCelestialCoordinates(float lat, float lng, float az, float alt)
{
/*
* Key:
* ------------ Local Coordinates -------------
* az = azimuth - angle around the horizon from due north to under POI (north has azimuth of 0m south has azimuth of 180)
* alt = altitude - angle from the horizon where the object is.
* lat = latitude
* long = Longitude
* lst = local sideral time - Greenwich meridian plus Longitude
* lha = local hour angle - It is the angle between the meridian of your Assumed Position and the meridian of the geographical position of the celestial body.
* ------------ Equatorial Coordinates ---------------
* ra = right ascention
* dec = declination angle
* ha = hour angle - angle between local meridian projected on celestial sphere, and right ascention of body
*
*
* CALCULATING: 'right ascension' (ra) and 'declination' (dec)
* 1) sin(alt) = sin(dec)sin(lat) + cos(dec)cos(lat)cos(ha)
* 2) sin(ha) = tan(az)[cos(ha)sin(lat) - tan(dec)cos(lat)]
* 3) ra = lst - ha
*
* Rearranging leads to:
* ha = arctan(x,y)
* x = sin(lat)cos(alt)cos(az) + cos(lat)sin(alt)
* y = cos(alt)sin(az)
*
* dec = arctan(x', y')
* x' = sin(az)cos(ha)sin(lat) - sin(ha)cos(az)
* y' = cos(lat)sin(az)
*/
//find coordinates assuming sidereal_time is 00::00::00
AAS2DCoordinate converted = AASCoordinateTransformation.Horizontal2Equatorial(az, alt, lat);
//adjust for local sideral_time
converted.X += (LocalSiderealTime(lng) * (360f / 24f));
return(converted);
}
