static int HorizontalCoords( out Spherical hor, double ecliptic_longitude, AstroTime time, RotationMatrix rot_ecl_hor) { var eclip = new Spherical( 0.0, /* being "on the ecliptic plane" means ecliptic latitude is zero. */ ecliptic_longitude, 1.0 /* any positive distance value will work fine. */ ); /* Convert ecliptic angular coordinates to ecliptic vector. */ AstroVector ecl_vec = Astronomy.VectorFromSphere(eclip, time); /* Use the rotation matrix to convert ecliptic vector to horizontal vector. */ AstroVector hor_vec = Astronomy.RotateVector(rot_ecl_hor, ecl_vec); /* Find horizontal angular coordinates, correcting for atmospheric refraction. */ hor = Astronomy.HorizonFromVector(hor_vec, Refraction.Normal); return(0); /* success */ }