Returns the difference in light-time, for a star, between the barycenter of the solar system and the observer (or the geocenter).

Namespace: ASCOM.Astrometry.NOVAS
Assembly: ASCOM.Astrometry (in ASCOM.Astrometry.dll) Version: 6.0.0.0 (6.1.1.2619)

Syntax

C#
public double DLight(
	double[] Pos1,
	double[] PosObs
)
Visual Basic
Public Function DLight ( _
	Pos1 As Double(), _
	PosObs As Double() _
) As Double
Visual C++
public:
virtual double DLight(
	array<double>^ Pos1, 
	array<double>^ PosObs
) sealed

Parameters

Pos1
Type: array<System..::..Double>[]()[][]
Position vector of star, with respect to origin at solar system barycenter.
PosObs
Type: array<System..::..Double>[]()[][]
Position vector of observer (or the geocenter), with respect to origin at solar system barycenter, components in AU.

Return Value

Difference in light time, in the sense star to barycenter minus star to earth, in days.

Remarks

Alternatively, this function returns the light-time from the observer (or the geocenter) to a point on a light ray that is closest to a specific solar system body. For this purpose, 'Pos1' is the position vector toward observed object, with respect to origin at observer (or the geocenter); 'PosObs' is the position vector of solar system body, with respect to origin at observer (or the geocenter), components in AU; and the returned value is the light time to point on line defined by 'Pos1' that is closest to solar system body (positive if light passes body before hitting observer, i.e., if 'Pos1' is within 90 degrees of 'PosObs').

See Also