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NOVAS31Cel2Ter Method
This function rotates a vector from the celestial to the terrestrial system. Specifically, it transforms a vector in the GCRS (a local space-fixed system) to the ITRS (a rotating earth-fixed system) by applying rotations for the GCRS-to-dynamical frame tie, precession, nutation, Earth rotation, and polar motion.

Namespace: ASCOM.Astrometry.NOVAS
Assembly: ASCOM.Astrometry (in ASCOM.Astrometry.dll) Version: 6.0.0.0 (6.2.0.2774)
Syntax
public short Cel2Ter(
	double JdHigh,
	double JdLow,
	double DeltaT,
	Method Method,
	Accuracy Accuracy,
	OutputVectorOption OutputOption,
	double xp,
	double yp,
	double[] VecT,
	ref double[] VecC
)

Parameters

JdHigh
Type: SystemDouble
High-order part of UT1 Julian date.
JdLow
Type: SystemDouble
Low-order part of UT1 Julian date.
DeltaT
Type: SystemDouble
Value of Delta T (= TT - UT1) at the input UT1 Julian date.
Method
Type: ASCOM.AstrometryMethod
Selection for method: 0 ... CIO-based method; 1 ... equinox-based method
Accuracy
Type: ASCOM.AstrometryAccuracy
Selection for accuracy
OutputOption
Type: ASCOM.AstrometryOutputVectorOption
0 ... The output vector is referred to GCRS axes; 1 ... The output vector is produced with respect to the equator and equinox of date. (See note 2 below)
xp
Type: SystemDouble
Conventionally-defined X coordinate of celestial intermediate pole with respect to ITRS pole, in arcseconds.
yp
Type: SystemDouble
Conventionally-defined Y coordinate of celestial intermediate pole with respect to ITRS pole, in arcseconds.
VecT
Type: SystemDouble
Position vector, geocentric equatorial rectangular coordinates, referred to GCRS axes (celestial system) or with respect to the equator and equinox of date, depending on 'option'.
VecC
Type: SystemDouble
Position vector, geocentric equatorial rectangular coordinates, referred to ITRS axes (terrestrial system).

Return Value

Type: Int16
    0 ... everything is ok
    1 ... invalid value of 'Accuracy'
    2 ... invalid value of 'Method'
 > 10 ... 10 + error from function 'CioLocation'
 > 20 ... 20 + error from function 'CioBasis'
 
Remarks
Note 1: 'x' = 'y' = 0 means no polar motion transformation.

Note2: 'option' = 1 only works for the equinox-based method.

See Also