ASCOM Library
SofaDtdb Method
Approximate TDB−TT for an observer on the Earth.
Definition
Namespace: ASCOM.Tools
Assembly: ASCOM.AstrometryTools (in ASCOM.AstrometryTools.dll) Version: 3.0.0-rc.1+86c25ce733aebb4d8b1b8a62e84770ea5e972bea
TDB−TT in seconds.
Assembly: ASCOM.AstrometryTools (in ASCOM.AstrometryTools.dll) Version: 3.0.0-rc.1+86c25ce733aebb4d8b1b8a62e84770ea5e972bea
C#
public static double Dtdb(
double date1,
double date2,
double ut,
double elong,
double u,
double v
)VB
Public Shared Function Dtdb (
date1 As Double,
date2 As Double,
ut As Double,
elong As Double,
u As Double,
v As Double
) As DoubleParameters
- date1 Double
- First part of the date as a 2-part Julian Date (TDB; TT is acceptable in practice).
- date2 Double
- Second part of the date as a 2-part Julian Date (TDB; TT is acceptable in practice).
- ut Double
- Universal time UT1 as a fraction of one day.
- elong Double
- Observer longitude (east positive, radians).
- u Double
- Distance from Earth spin axis (km).
- v Double
- Distance north of the equatorial plane (km).
Return Value
DoubleTDB−TT in seconds.
Remarks
This is a model of the quasi-periodic part of the TT/TCB relationship, dominated by an annual term (~1.7 ms).
Providing zero for u and v removes the topocentric contribution.