libnova2

libnova2 is a general purpose, double precision, Celestial Mechanics, Astrometry and Astrodynamics library. It is a successor to libnova with the significant change being use of radians instead of degrees.

Features

• High Precision: 1 arc second or better.
• Ephemerides:
  • Major Planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto.
  • Sun & Moon (ELP82).
  • Minor Bodies: Asteroids and Comets.
• Astrometry:
  • Aberration, Nutation, Precession, Proper Motion.
  • Refraction, Parallax, Airmass.
• Time Systems:
  • Julian Day, Sidereal Time, Dynamical Time, Heliocentric Time.
• Coordinates:
  • Transformations: Equatorial, Ecliptic, Horizontal, Galactic.
  • Rise, Set, and Transit times.
  • Angular Separation.

Requirements

• C compiler (GCC, Clang, MSVC)
• CMake (3.25 or later)
• Optional:
  • kconfig-frontends (for menuconfig configuration)
  • Doxygen (for API documentation)
  • dpkg (for building Debian packages)
  • rpm / rpmbuild (for building RPM packages)

Building

libnova2 uses CMake for its build system.

1. Configure

mkdir build && cd build
cmake ..

Common Options:

• -DBUILD_SHARED_LIBS=OFF: Build static libraries (default is ON).
• -DENABLE_SIMD=ON: Enable AVX SIMD optimizations (Linux/GCC only). Uses auto-vectorization and libmvec for fast math.
• -DCMAKE_BUILD_TYPE=Release: Optimized build.
• -DCMAKE_INSTALL_PREFIX=/usr: Installation destination.

2. Configure Modules (Optional)

You can enable or disable specific modules (e.g., planets, theories) using the Kconfig interface:

make menuconfig

(Requires kconfig-frontends)

This creates a .config file that CMake will use to select source files.

3. Build

make

4. Install

sudo make install

5. Debian / RPM Packages

You can build .deb and .rpm packages using CPack (from the build directory):

make package

6. Python Package

A Python wrapper is available. You can generate a source distribution and a .whl package ready for pip using the python-package target:

make python-package

The output files will be created in the python/dist/ directory. You can then install the .whl file using pip:

pip install python/dist/libnova2-*.whl

Cross-Compilation

libnova2 supports cross-compilation for embedded targets (e.g., ESP32, ARM).

1. Toolchain File

Create a CMake toolchain file for your target. A sample is provided in cmake/toolchain-xtensa-sample.cmake.

2. Configure with Toolchain

mkdir build-cross && cd build-cross
cmake -DCMAKE_TOOLCHAIN_FILE=../cmake/toolchain-xtensa-sample.cmake \
      -DBUILD_TESTING=OFF \
      -DBUILD_EXAMPLES=OFF \
      ..

Key Cross-Compilation Options:

• -DBUILD_TESTING=OFF: Disable unit tests (they likely won't run on the build host).
• -DBUILD_EXAMPLES=OFF: Disable example programs.
• HAVE_LIBM: The build system automatically detects if libm is needed/available, replacing hardcoded UNIX checks.

3. Cross Build

make

Running Tests

If you built the tests (default on host builds):

ctest --output-on-failure

Or run the test executable details:

./lntest/libnova2_test_exec

Documentation

To generate the HTML API documentation:

make doc

Output is in doc/html/index.html.

Usage

Include the main header:

#include <libnova2/libnova2.h>

Link against libnova2 (and libm if static/required):

cc my_program.c -lnova2 -lm -o my_program

For more examples, see the examples/ directory.