NOVAS: Class presenting the contents of the NOVAS 2 library. NOVAS was developed by the Astronomical Applications department of the United States Naval Observatory. The C language version of NOVAS was developed by John Bangert at USNO/AA.

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


public class NOVAS2
Visual Basic
Public Class NOVAS2
Visual C++
public ref class NOVAS2


The NOVAS class is a STATIC class and is the component of preference for .NET programmers. This means that you do not have to create an instance of the class in order to access its members. Instead you reference them directly from the class. So, this works:
rc = ASCOM.Astrometry.NOVAS2.AppStar(tjd, earth, star, ra, dec)
while this does not work:
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 real-time star data from the USNO web site. Values provided by this NOVAS2 implementation agree on average to about 50 milli arc-seconds 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.

Inheritance Hierarchy


See Also