Which NOVAS?

The ASCOM updated Platform has three astrometric components:

  • Transform
  • NOVASCOM
  • NOVAS2
Surely an embarrassment of riches? In fact these components provide different capabilities and are targetted at different requirements and uses as described below.

Transform

This simple component is designed for the telescope or dome driver author who simply needs to convert between J2000 RA/DEC co-ordinates and local topocentric RA/DEC and AZ/EL co-ordinates and vice-versa. The Topocentric RA/DEC and AZ/EL coordinates can also be corrected for refraction effects. The component is built on the established NOVAS3.1 supervisory library routines.

This component can be used directly by .NET based applications and is also exposed as a COM object to enable use by scripting and other languages.

NOVASCOM

This component is a refactoring of the NOVASCOM component authored by Bob Denny in 2001, which was provided as an optional download component in ASCOM Platforms 4 and 5. It is now integrated in the platform release and is appropriate for applications requiring accurate ephemerides of the major planets and in minor planet astrometrics. It can also handle star co-ordinate conversion from J2000 to Topocentric.

The component translates from J2000 to topocentric but not vice versa. It is built on the NOVAS2 astrometric library routines and the Kepler planetary ephemerides component.

This component can be used directly by .NET based applications and is also exposed as a COM object to enable use by scripting and other languages.

NOVAS2

This component is for demanding applications that require access to the fundamental routines in the NOVAS2 library. It contains a range of supervisory routines that provide access to high level functions and an extensive range of intermediate and basic level routines dedicated to lower level astrometric functions.

The calling interface is close to the original C interface and most calculated values are passed back through reference parameters.

This component can be used directly by .NET based applications and is also exposed as a COM object to enable use by scripting and other languages. Full functionality is available through the .NET interface, however, recent testing (April 2012) has shown that many methods are not accessible through COM interop because a number of parameters are passed by Reference or use structures that do not pass across the COM interface (this is a technical COM limitation, not an ASCOM limitation).

NOVAS3

This component is a shell for the NOVAS 3 library released in December 2009 for demanding applications that require access to the fundamental routines in the NOVAS3 library, the latest JPL DE421 planetary and lunar ephemerises or to calculations based on the IAU 2000 reference systems resolution. It contains a range of supervisory routines that provide access to high level functions and an extensive range of intermediate and basic level routines dedicated to lower level astrometric functions.

The calling interface is close to the original C interface and most calculated values are passed back through reference parameters.

This component can be used directly by .NET based applications and is also exposed as a COM object to enable use by scripting and other languages. Full functionality is available through the .NET interface, however, recent testing (April 2012) has shown that many methods are not accessible through COM interop because a number of method parameters are passed by Reference and use structures that do not pass across the COM interface (this is a technical COM limitation, not an ASCOM limitation).