/// <summary>
/// Handles WCS calculations based on CROTA2, CDELT and tangential projection
/// </summary>
/// <param name="crval1">Reference x pixel value</param>
/// <param name="crval2">Reference y pixel value</param>
/// <param name="crpix1">Reference pixel x</param>
/// <param name="crpix2">Reference pixel y</param>
/// <param name="cdelta1">per pixel increment along RA</param>
/// <param name="cdelta2">per pixel increment along DEC</param>
/// <param name="crota2">Rotation in degrees</param>
/// <remarks>Vertically and horizontally flipped images don't work as of now</remarks>
public WorldCoordinateSystem(
double crval1,
double crval2,
double crpix1,
double crpix2,
double cdelta1,
double cdelta2,
double crota2
)
{
Point = new Point(crpix1, crpix2);
Coordinates = new Coordinates(Angle.ByDegree(crval1), Angle.ByDegree(crval2), Epoch.J2000);
if (cdelta1 >= 0 || cdelta2 < 0)
{
Flipped = true;
}
if (!Flipped)
{
Rotation = Astrometry.EuclidianModulus(crota2, 360);
}
else
{
Rotation = Astrometry.EuclidianModulus(-crota2, 360);
}
PixelScaleX = Astrometry.DegreeToArcsec(Math.Abs(cdelta1));
PixelScaleY = Astrometry.DegreeToArcsec(Math.Abs(cdelta2));
}
protected override double AdjustAltitude(Body body)
{
/* Readjust moon altitude based on earth radius and refraction */
var horizon = 90.0;
var location = new NOVAS.OnSurface()
{
Latitude = Latitude,
Longitude = Longitude
};
var refraction = NOVAS.Refract(ref location, NOVAS.RefractionOption.StandardRefraction, horizon);;
var altitude = body.Altitude - Astrometry.ToDegree(Earth.Radius) / body.Distance + Astrometry.ToDegree(body.Radius) / body.Distance + refraction;
return(altitude);
}
public Coordinates Transform(Epoch epoch)
{
var now = DateTime.Now;
var jdUTC = Astrometry.GetJulianDate(now);
var zenithDistance = Astrometry.ToRadians(90d - Altitude.Degree);
var deltaUT = Astrometry.DeltaUT(now);
var raRad = 0d;
var decRad = 0d;
SOFA.TopocentricToCelestial("A", Azimuth.Radians, zenithDistance, jdUTC, 0d, deltaUT, Longitude.Radians, Latitude.Radians, 0d, 0d, 0d, 0d, 0d, 0d, 0d, ref raRad, ref decRad);
var ra = Angle.ByRadians(raRad);
var dec = Angle.ByRadians(decRad);
var coordinates = new Coordinates(ra, dec, Epoch.J2000);
return(coordinates.Transform(epoch));
}
/// <summary>
/// Handles WCS calculations based on CDn_m matrix and tangential projection
/// </summary>
/// <param name="crval1">Reference x pixel value</param>
/// <param name="crval2">Reference y pixel value</param>
/// <param name="crpix1">Reference pixel x</param>
/// <param name="crpix2">Reference pixel y</param>
/// <param name="cd1_1">CDn_m tranformation matrix</param>
/// <param name="cd1_2">CDn_m tranformation matrix</param>
/// <param name="cd2_1">CDn_m tranformation matrix</param>
/// <param name="cd2_2">CDn_m tranformation matrix</param>
/// <remarks>
/// http://hosting.astro.cornell.edu/~vassilis/isocont/node17.html
/// https://www.astro.rug.nl/~gipsy/tsk/fitsreproj.dc1
/// Vertically and horizontally flipped images don't work as of now
/// </remarks>
public WorldCoordinateSystem(
double crval1,
double crval2,
double crpix1,
double crpix2,
double cd1_1,
double cd1_2,
double cd2_1,
double cd2_2
)
{
Point = new Point(crpix1, crpix2);
Coordinates = new Coordinates(Angle.ByDegree(crval1), Angle.ByDegree(crval2), Epoch.J2000);
var determinant = cd1_1 * cd2_2 - cd1_2 * cd2_1;
var sign = 1;
if (determinant < 0)
{
sign = -1;
}
var cdelta1 = sign * Math.Sqrt(cd1_1 * cd1_1 + cd2_1 * cd2_1);
var cdelta2 = Math.Sqrt(cd1_2 * cd1_2 + cd2_2 * cd2_2);
if (cdelta1 >= 0 || cdelta2 < 0)
{
Flipped = true;
}
var rot1_cd = Math.Atan2(sign * cd1_2, cd2_2);
var rot2_cd = Math.Atan2(sign * cd1_1, cd2_1) - Math.PI / 2d;
var rotation = Astrometry.ToDegree(Flipped ? -rot2_cd : rot2_cd);
var skew = Astrometry.ToDegree(Math.Abs(rot1_cd - rot2_cd));
//Approximation as the matrix can account for skewed axes
Rotation = Astrometry.EuclidianModulus(rotation, 360);
PixelScaleX = Astrometry.DegreeToArcsec(Math.Abs(cdelta1));
PixelScaleY = Astrometry.DegreeToArcsec(Math.Abs(cdelta2));
}
public Task Calculate()
{
return(Task.Run(() => {
var jd = Astrometry.GetJulianDate(Date);
var deltaT = Astrometry.DeltaT(Date);
var location = new NOVAS.OnSurface()
{
Latitude = Latitude,
Longitude = Longitude
};
var observer = new NOVAS.Observer()
{
OnSurf = location,
Where = (short)NOVAS.ObserverLocation.EarthGeoCenter
};
var obj = new NOVAS.CelestialObject()
{
Name = Name,
Number = (short)BodyNumber,
Star = new NOVAS.CatalogueEntry(),
Type = (short)NOVAS.ObjectType.MajorPlanetSunOrMoon
};
var objPosition = new NOVAS.SkyPosition();
NOVAS.Place(jd + Astrometry.SecondsToDays(deltaT), obj, observer, deltaT, NOVAS.CoordinateSystem.EquinoxOfDate, NOVAS.Accuracy.Full, ref objPosition);
this.Distance = Astrometry.AUToKilometer(objPosition.Dis);
var siderealTime = Astrometry.GetLocalSiderealTime(Date, Longitude);
var hourAngle = Astrometry.HoursToDegrees(Astrometry.GetHourAngle(siderealTime, objPosition.RA));
this.Altitude = Astrometry.GetAltitude(hourAngle, Latitude, objPosition.Dec);
}));
}
public static double FieldOfView(double arcsecPerPixel, double width)
{
return(Astrometry.ArcsecToArcmin(arcsecPerPixel * width));
}
public static double MaxFieldOfView(double arcsecPerPixel, double width, double height)
{
return(Astrometry.ArcsecToArcmin(arcsecPerPixel * Math.Max(width, height)));
}
public override string ToString()
{
return(Astrometry.DegreesToDMS(Degree));
}
public static Angle ByRadians(double radians)
{
var degree = Astrometry.ToDegree(radians);
return(new Angle(Astrometry.ToDegree(radians), radians, Astrometry.DegreesToHours(degree)));
}
public static Angle ByDegree(double degree)
{
return(new Angle(degree, Astrometry.ToRadians(degree), Astrometry.DegreesToHours(degree)));
}
public static Angle ByHours(double hours)
{
var degree = Astrometry.HoursToDegrees(hours);
return(new Angle(degree, Astrometry.ToRadians(degree), hours));
}
