NOVAS 3.1.1 - Python
Naval Observatory Vector Astrometry Software
Python Edition 3.1.1 (13 October 2015)
is currently available for Mac OSX,
Linux, and Unix at the
Astrophysics Source Code Library
NOVAS is an integrated package of
functions for computing various commonly needed quantities in positional
astronomy. The package can supply, in one or two function calls,
the instantaneous coordinates of any star or planet in a variety of coordinate
systems. At a lower level, NOVAS also provides astrometric utility
transformations, such as those for precession, nutation, aberration, parallax,
and gravitational deflection of light. The computations are accurate to better
than one milliarcsecond. The NOVAS library is an easy-to-use facility that can
be incorporated into data reduction programs, telescope control systems, and
simulations. The U.S. parts of
The Astronomical Almanac
are prepared using NOVAS.
C editions of
NOVAS are also available. See the
NOVAS overview for more
NOVAS Python borrows its underlying computational code from the
and implements nearly all of the
features found in the C edition. Notable options of NOVAS C not
currently available in NOVAS Python include the ability to calculate the
Celestial Intermediate Origin (CIO) using an external file and direct support for the external
USNO/AE98 minor planet ephemerides.
Function calls in NOVAS Python are generally synonymous with the corresponding ones
in NOVAS C, except some arguments used to define accuracy, coordinate systems, and
calculation methods are treated as optional parameters with default values.
NOVAS Python provides a
file with further information as well as
within functions to explain usage. Because NOVAS Python is based on the NOVAS C functions, the
NOVAS C User's Guide
provides expanded explanations of the most frequently called functions with hypertext cross-references.
Additional information about the computation of nutation in NOVAS is available in
USNO Circular 181.
For most high-level calculations, NOVAS requires access to the position and
velocity vectors of solar system objects as a function of time. NOVAS function
ephemeris provides these data. While in NOVAS C, the user may choose
among three versions of solarsystem to use at compile-time, NOVAS Python
only provides solarsystem version 1,
an all C-based interface to the planetary and lunar ephemerides produced by the Jet
Propulsion Laboratory (JPL). Like its C counterpart, NOVAS Python requires a binary ephemeris file,
such as the one the user can create from
file discusses installation options. The
User's Guide provides more information on the use of ephemeris and
solarsystem, including the specification of their calls, and guidance on
obtaining and installing the JPL ephemerides manually.
For known issues with the code, see NOVAS
User Updates and FAQ.
Direct questions, comments, and problem reports to our help desk.