Transform apparent equatorial coordinates to horizon coordinates

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

Syntax

C#
public void Equ2Hor(
	double tjd,
	double deltat,
	double x,
	double y,
	ref SiteInfo location,
	double ra,
	double dec,
	RefractionOption ref_option,
	ref double zd,
	ref double az,
	ref double rar,
	ref double decr
)
Visual Basic
Public Sub Equ2Hor ( _
	tjd As Double, _
	deltat As Double, _
	x As Double, _
	y As Double, _
	ByRef location As SiteInfo, _
	ra As Double, _
	dec As Double, _
	ref_option As RefractionOption, _
	ByRef zd As Double, _
	ByRef az As Double, _
	ByRef rar As Double, _
	ByRef decr As Double _
)
Visual C++
public:
virtual void Equ2Hor(
	double tjd, 
	double deltat, 
	double x, 
	double y, 
	SiteInfo% location, 
	double ra, 
	double dec, 
	RefractionOption ref_option, 
	double% zd, 
	double% az, 
	double% rar, 
	double% decr
) sealed

Parameters

tjd
Type: System..::..Double
TT (or TDT) Julian date.
deltat
Type: System..::..Double
Difference TT (or TDT)-UT1 at 'tjd', in seconds.
x
Type: System..::..Double
Conventionally-defined x coordinate of celestial ephemeris pole with respect to IERS reference pole, in arcseconds.
y
Type: System..::..Double
Conventionally-defined y coordinate of celestial ephemeris pole with respect to IERS reference pole, in arcseconds.
location
Type: ASCOM.Astrometry..::..SiteInfo%
structure containing observer's location
ra
Type: System..::..Double
Topocentric right ascension of object of interest, in hours, referred to true equator and equinox of date.
dec
Type: System..::..Double
Topocentric declination of object of interest, in degrees, referred to true equator and equinox of date.
ref_option
Type: ASCOM.Astrometry..::..RefractionOption
Refraction option
zd
Type: System..::..Double%
OUT: Topocentric zenith distance in degrees, affected by refraction if 'ref_option' is non-zero.
az
Type: System..::..Double%
OUT: Topocentric azimuth (measured east from north) in degrees.
rar
Type: System..::..Double%
OUT: Topocentric right ascension of object of interest, in hours, referred to true equator and equinox of date, affected by refraction if 'ref_option' is non-zero.
decr
Type: System..::..Double%
OUT: Topocentric declination of object of interest, in degrees, referred to true equator and equinox of date, affected by refraction if 'ref_option' is non-zero.

Remarks

This function transforms apparent equatorial coordinates (right ascension and declination) to horizon coordinates (zenith distance and azimuth). It uses a method that properly accounts for polar motion, which is significant at the sub-arcsecond level. This function can also adjust coordinates for atmospheric refraction.

See Also