static public Coordinates HorizonToEquitorial(Coordinates altAz, Coordinates location, Date utc) { double hourAngle = MstFromUTC2(utc, location.Lng);// -(equitorial.RA * 15); double haLocal; double declination; Vector2d raDec = AltAzToRaDec(altAz.Alt * RC, altAz.Az * RC, location.Lat * RC); haLocal = raDec.X; declination = raDec.Y; double ha = (haLocal / RC); hourAngle += ha; if (hourAngle < 0) { hourAngle += 360.00; } if (hourAngle > 360) { hourAngle -= 360; } return(Coordinates.FromRaDec(hourAngle / 15, declination / RC)); }