I am creating a planetarium program using Unity3D and C# to plot out stars from the Hipparcos catalogue. Using the Plx, _RA.icrs and _DE.icrs columns of the dataset, I have managed to work the distance in parsecs and work out a cartesian set of coordinates.
Simulation Class...
public class Simulation : MonoBehaviour
{
public IEnumerator loadStars()
{
starsLoaded = 0;
var stopWatch = new Stopwatch();
stopWatch.Start();
// Use the last frame duration as a guide how long one frame should take
var targetMilliseconds = Time.deltaTime * 100f;
for (int i = 0; i < totalStars; i++)
{
Double.TryParse(datasetTable[i, 3], out double test);
if (!(datasetTable[i, 12] == null) && !(datasetTable[i, 13] == null) && !(datasetTable[i, 6] == null))
{
GameObject thisStar = Instantiate(starPrefab, transform.position, transform.rotation) as GameObject;
thisStar.transform.parent = starHolder.transform;
Int32.TryParse(datasetTable[i, 0], out (thisStar.GetComponent<Star>().ID));
Double.TryParse(datasetTable[i, 12], out (thisStar.GetComponent<Star>().RA));
Double.TryParse(datasetTable[i, 13], out (thisStar.GetComponent<Star>().DE));
Double.TryParse(datasetTable[i, 3], out (thisStar.GetComponent<Star>().Vmag));
Double.TryParse(datasetTable[i, 6], out (thisStar.GetComponent<Star>().Plx));
Double.TryParse(datasetTable[i, 10], out (thisStar.GetComponent<Star>().CI));
}
if (stopWatch.ElapsedMilliseconds > targetMilliseconds)
{
yield return null;
stopWatch.Restart();
}
starsLoaded++;
}
}
}
Star class:
public class Star : MonoBehaviour
{
/// <summary>
/// Identifier (HIP number). "HIP" is appended to the ID, for Hipparcos
/// </summary>
[SerializeField] public int ID; // { get; set; }
/// <summary>
/// Right Ascension (J2000) in degrees.
/// </summary>
[SerializeField] public double RA; //{ get; set; }
/// <summary>
/// Declination (J2000) in degrees.
/// </summary>
[SerializeField] public double DE; //{ get; set; }
/// <summary>
/// Magnitude in Johnson V
/// </summary>
[SerializeField] public double Vmag; //{ get; set; }
/// <summary>
/// Trigonometric parallax, measured in milli-seconds of arc
/// </summary>
[SerializeField] public double Plx; //{ get; set; }
/// <summary>
/// Colour index in Johnson B-V colour
/// </summary>
[SerializeField] public double CI; //{ get; set; }
/// <summary>
/// Distance of the star from the centre of Earth measured in kilometres
/// </summary>
[SerializeField] public double distanceFromEarth;
/// <summary>
/// Cartesian (X,Y,Z) positioning of the star
/// </summary>
[SerializeField] Vector3 cartesianPositioning;
// Start is called before the first frame update
void Start()
{
positionStar();
}
private void distanceFromEarthCalc()
{
// Convert Plx from milliarcseconds to arcseconds (seconds of arc)
double PlxSOA = Plx / 1000;
// Calculate distance from equation d=1/p
// distance d is measured in parsecs and the parallax angle p is measured in arcseconds.
double dPC = 1 / PlxSOA;
/// Convert parsecs to kilomentres
/// Conversion can bbe found here:
/// https://en.wikipedia.org/wiki/Parsec
///
/// QUICK NOTE: converting to km causes issues with unity - values are too high
/// maybe work with parsecs instead?
///
//distanceFromEarth = (dPC * (96939420213600000 / math.PI_DBL)) / 1000;
//distanceFromEarth = distanceFromEarth / 10000; // metres to kilometres
distanceFromEarth = dPC * 10; // multiplied by 10 to move stars away from camera
}
private void cartesianPositioningCalc()
{
distanceFromEarthCalc();
double RA_rad = RA * (math.PI_DBL / 180);
double DE_rad = DE * (math.PI_DBL / 180);
cartesianPositioning.x = (float)(distanceFromEarth * (math.cos(DE_rad)) * (math.cos(RA_rad)));
cartesianPositioning.y = (float)(distanceFromEarth * (math.cos(DE_rad)) * (math.sin(RA_rad)));
cartesianPositioning.z = (float)(distanceFromEarth * (math.sin(DE_rad)));
}
private void positionStar()
{
cartesianPositioningCalc();
gameObject.transform.position = cartesianPositioning;
gameObject.transform.localScale = new Vector3(2, 2, 2);
}
}
View from the camera:
3D view of the scene (the camera's orientation is shown by the arrows):
With the image from the camera, I tried uploading it to http://nova.astrometry.net/ but was unable to find stars/constellations.
So I thought about normalising the vectors of the stars.
With the Simulation class unchanged, I changed the distanceFromEarth variable in the Star class to 900 to normalise the vectors (each star will not have the same distance from the centre)
View from the camera:
3D view of the scene (the camera's orientation is shown by the arrows):
Even after the normalisation, uploading the image of the view from the camera to the image processing website resulted in no stars/constellations being detected.
What am I doing wrong, why aren't stars and constellation detected?
