**3. Function Overview**

The following functions are contained in file **novas.c**:

**Entry name**

**Level**

**Purpose**

supervisory

Computes the geocentric apparent place of a star, given its J2000.0 catalog mean place.

supervisory

Computes the topocentric apparent place of a star, given its J2000.0 catalog mean place

and geographic location of observer.

supervisory

Computes the geocentric apparent place of a planet or other solar system body.

supervisory

Computes the topocentric apparent place of a planet or other solar system body, given

geographic location of observer.

supervisory

Computes the "virtual place" of a star, given its J2000.0 catalog mean place.

supervisory

Computes the "local place" of a star, given its J2000.0 catalog mean place and

geographic location of observer.

supervisory

Computes the "virtual place" of a planet or other solar system body.

supervisory

Computes the "local place" of a planet or other solar system body, given geographic

location of observer.

supervisory

Computes the astrometric place of a star, given its J2000.0 catalog mean place.

supervisory

Computes the astrometric place of a planet or other solar system body.

*mean_star*

supervisory

Computes the J2000.0 mean place of a star, given its apparent place.

supervisory

Computes Greenwich sidereal time, either mean or apparent.

*pnsw*

supervisory

Transforms arbitrary vector in rotating Earth-fixed (geographic) system to space-fixed

(J2000.0) system.

*get_earth*

utility

Provides barycentric and heliocentric position and velocity of the Earth at a TDT date.

*spin*

utility

Rotates vector by angle equal to sidereal time.

*wobble*

utility

Adjusts Earth-fixed vector for polar motion.

*proper_motion*

utility

Updates the position vector of a star to allow for its space motion.

*geocentric*

utility

Changes origin of coordinates from barycenter of solar system to center of mass of

Earth.

*aberration*

utility

Adjusts position vector for aberration of light due to motion of Earth.

utility

Applies precession to position vector.

*nutate*

utility

Applies nutation to position vector.

*sun_field*

utility

Adjusts position vector for deflection of light by Sun's gravitational field.

*terra*

utility

Converts geographic coordinates to geocentric position vector.

*vector2radec*

utility

Converts position vector to RA and declination.

*angle2vector*

utility

Converts RA, declination, and distance to a position vector.

*starvectors*

utility

Converts RA, declination, proper motion, etc., to position and velocity vectors.

*calc_nutation*

basic

Evaluates nutation series.

basic

Provides information on orientation of Earth's axis: obliquity, nutation parameters, etc.

*convert_tdb2tdt*

basic

Converts Terrestrial Dynamical Time (TDT) to Barycentric Dynamical Time (TDB).