NOVAS2 Class 
Note: This API is now obsolete.
Namespace: ASCOM.Astrometry.NOVAS
The NOVAS2 type exposes the following members.
Name  Description  

Aberration 
Corrects position vector for aberration of light.
 
AppPlanet 
Compute the apparent place of a planet or other solar system body.
 
AppStar 
Computes the apparent place of a star
 
AstroPlanet 
Computes the astrometric place of a planet or other solar system body.
 
AstroStar 
Computes the astrometric place of a star
 
BaryToGeo 
Moves the origin of coordinates from the barycenter of the solar system to the center of mass of the Earth
 
CalDate 
Compute a date on the Gregorian calendar given the Julian date.
 
CelPole 
This function allows for the specification of celestial pole offsets for highprecision applications.
 
DeltaT 
Return the value of DeltaT for the given Julian date
 
EarthTilt 
Computes quantities related to the orientation of the Earth's rotation axis at Julian date 'tjd'.
 
Ephemeris 
Retrieves the position and velocity of a body from a fundamental ephemeris.
 
Equ2Hor 
Transform apparent equatorial coordinates to horizon coordinates
 
FundArgs 
To compute the fundamental arguments.
 
GetEarth 
Obtains the barycentric and heliocentric positions and velocities of the Earth from the solar system ephemeris.
 
JulianDate 
This function will compute the Julian date for a given calendar date (year, month, day, hour).
 
LocalPlanet 
Computes the local place of a planet or other solar system body, given the location of the observer.
 
LocalStar 
Computes the local place of a star
 
MakeCatEntry 
To create a structure of type 'cat_entry' containing catalog data for a star or "starlike" object.
 
MeanStar 
Computes the mean place of a star for J2000.0
 
Nutate 
Nutates equatorial rectangular coordinates from mean equator and equinox of epoch to true equator and equinox of epoch.
 
NutationAngles 
Provides fast evaluation of the nutation components according to the 1980 IAU Theory of Nutation.
 
Pnsw 
Transforms a vector from an Earthfixed geographic system to a spacefixed system
 
Precession 
Precesses equatorial rectangular coordinates from one epoch to another.
 
ProperMotion 
Applies proper motion, including foreshortening effects, to a star's position.
 
RADec2Vector 
Converts equatorial spherical coordinates to a vector (equatorial rectangular coordinates).
 
Refract 
Computes atmospheric refraction in zenith distance.
 
SetBody 
Sets up a structure of type 'body'  defining a celestial object based on the input parameters.
 
SiderealTime 
Computes the Greenwich apparent sidereal time, at Julian date 'jd_high' + 'jd_low'.
 
SolarSystem 
Provides the position and velocity of the Earth
 
Spin 
Transforms geocentric rectangular coordinates from rotating system to nonrotating system
 
StarVectors 
Converts angular quanities for stars to vectors.
 
SunEph 
Compute equatorial spherical coordinates of Sun referred to the mean equator and equinox of date.
 
SunField 
Corrects position vector for the deflection of light in the gravitational field of the Sun.
 
Tdb2Tdt 
Converts TDB to TT or TDT
 
Terra 
Computes the position and velocity vectors of a terrestrial observer with respect to the center of the Earth.
 
TopoPlanet 
Computes the topocentric place of a planet, given the location of the observer.
 
TopoStar 
Computes the topocentric place of a star
 
TransformCat 
To transform a star's catalog quantities for a change of epoch and/or equator and equinox.
 
TransformHip 
To convert Hipparcos data at epoch J1991.25 to epoch J2000.0 and FK5style units.
 
Vector2RADec 
Converts an vector in equatorial rectangular coordinates to equatorial spherical coordinates.
 
VirtualPlanet 
Computes the virtual place of a planet or other solar system body.
 
VirtualStar 
Computes the virtual place of a star
 
Wobble 
Corrects Earthfixed geocentric rectangular coordinates for polar motion.

rc = ASCOM.Astrometry.NOVAS2.AppStar(tjd, earth, star, ra, dec)
Dim Nov as New ASCOM.Astrometry.NOVAS2
rc = Nov.AppStar(tjd, earth, star, ra, dec)
Method names are identical to those used in NOVAS2, as are almost all paramaters. There are a few changes that introduce some new structures but these should be self explanatory. One significant difference is that position and velocity vectors are returned as structures rather than double arrays. This was done to make type checking more effective.
Testing of the high level supervisory functions has been carried out using realtime star data from the USNO web site. Values provided by this NOVAS2 implementation agree on average to about 50 milli arcseconds with current USNO web site values.
This class is implemented using a thin layer of .NET code that calls functions in either a 32 or 64 bit compiled version of the unmodified C code from ther USNO web site. The .NET code does not carry out calculations itself, it simply handles any interface presentation differences and calls the relevant 32 or 64bit code according to its environment.
Note: This class only supports Earth in the XXXXPlanet classes, which is a consequence of the implementation used. Please use the NOVAS3.1 or later classes in applications that require planetary or moon ephemeredes as these classes can access the JPL 421 planetary ephemeris data provided as part of the ASCOM distribution.