/// <summary>
/// Normal. Calculate the Cartesian normal vector
/// corresponding to the PointEq p(ra,dec).
/// </summary>
/// <param name="p">PointEq object</param>
/// <returns>Array of 3 doubles, a 3-vector</returns>
public static double[] Normal(PointEq p)
{
double[] n = new double[3];
n[0] = Math.Cos(D2R * p.dec) * Math.Cos(D2R * p.ra);
n[1] = Math.Cos(D2R * p.dec) * Math.Sin(D2R * p.ra);
n[2] = Math.Sin(D2R * p.dec);
return(n);
}
/// <summary>
/// ScreenToEq. Maps a screen coordinate to an (ra,dec).
/// This is the inverse coordinate transformation function
/// </summary>
/// <param name="p">The screen coordinate of the point</param>
public PointEq ScreenToEq(PointF p)
{
double[] r = new Double[3];
//----------------------------------------
// first subtract the offset, and rescale
//----------------------------------------
PointF q = new PointF((float)((cOffset.X - p.X) / scale), (float)((cOffset.Y - p.Y) / scale));
//------------------------------------------------
// now these are the dot products with w and u
// compute the dot product with the normal vector
//------------------------------------------------
double qdec = 90 * q.Y;
double qra = 180 + 180 * q.X * Math.Cos(qdec * V3.D2R);
PointEq g = new PointEq(qra, qdec);
return(g);
}
/// <summary>
/// ScreenToEq. Maps a screen coordinate to an (ra,dec).
/// This is the inverse coordinate transformation function
/// </summary>
/// <param name="p">The screen coordinate of the point</param>
public PointEq ScreenToEq(PointF p)
{
double[] r = new Double[3];
//----------------------------------------
// first subtract the offset, and rescale
//----------------------------------------
PointF q = new PointF((float)((cOffset.X - p.X) / scale), (float)((cOffset.Y - p.Y) / scale));
//------------------------------------------------
// now these are the dot products with w and u
// compute the dot product with the normal vector
//------------------------------------------------
double gn = 1.0 - q.X * q.X - q.Y * q.Y;
gn = Math.Sqrt(gn);
for (int i = 0; i < 3; i++)
{
r[i] = gn * n[i] + q.X * w[i] + q.Y * u[i];
}
PointEq g = V3.ToEq(r);
return(g);
}
/// <summary>
/// ToEq. Calculate the Equatorial point corresponding to
/// a Cartesian normal vector (x,y,z).
/// </summary>
/// <param name="x_">Cartesian x</param>
/// <param name="y_">Cartesian y</param>
/// <param name="z_">Cartesian z</param>
/// <returns>Array of 2 doubles, a 2-vector</returns>
public static PointEq ToEq(double[] r)
{
double _dec = Math.Asin(r[2]) / D2R;
double _ra = 0.0;
// catch r[0]=r[1]=0 case, the north/south pole
if (Math.Abs(r[0]) < 1.0E-9 && Math.Abs(r[1]) < 1.0E-9)
{
_dec = 90.0 * r[2];
}
else
{
_ra = Math.Atan2(r[1], r[0]) / D2R;
if (_ra < 0)
{
_ra += 360.0;
}
}
PointEq p = new PointEq(_ra, _dec);
return(p);
}
public PointF EqToScreen(PointEq e, float size_)
{
return(EqToScreen(e.ra, e.dec, size_));
}