Naval Observatory Vector Astrometry Subroutines

Version : 2.0.1
Author(s) : Astronomical Applications Dept. U.S. Naval Observatory
License : GPL
Website :

Disk space required for installation is 2.93 Mb

The following printable documents will be installed :


The Naval Observatory Vector Astrometry Subroutines, NOVAS, is an integrated package of source-code modules for computing a wide variety of common astrometric quantities and transformations. The package can provide, in one function call, the instantaneous coordinates (apparent, topocentric, or astrometric place) of any star or planet. At a lower level, NOVAS also provides general astrometric utility transformations, such as those for precession, nutation, aberration, parallax, and the gravitational deflection of light. The computations are highly precise. The NOVAS algorithms are, in fact, virtually identical to those now used in the production of The Astronomical Almanac. NOVAS is easy-to-use and can be incorporated into data reduction programs, telescope control systems, and simulations.

NOVAS-C uses, as input, astrometric reference data that is expressed in the International Astronomical Union (IAU) J2000.0 system. In particular, NOVAS-C 2.0 supports (but is not limited to) data that conforms to the International Celestial Reference System (ICRS), adopted by the IAU in 1996. ICRS-compatible data includes the Hipparcos and Tycho Catalogues, the ACT Reference Catalog, the International Celestial Reference Frame (ICRF), the Jet Propulsion Laboratory's DE405 planetary ephemeris, and Earth orientation measurements from the International Earth Rotation Service (IERS). The list of ICRS-compatible data of various types is continually expanding. NOVAS-C can also be used with data conforming to the FK5 system.

Effective use of NOVAS-C requires some background in positional astronomy and considerable programming experience. Please read the accompanying documentation (in file novasguide.pdf) before attempting to use the software.