Astronoby

Ruby library to provide a useful API to compute astronomical calculations.

Some algorithms are based on the following astrometry books:

• Astronomical Algorithms by Jean Meeus
• Celestial Calculations by J. L. Lawrence
• Practical Astronomy with your Calculator or Spreadsheet by Peter Duffet-Smith and Jonathan Zwart

Solar System body's positions are computed based on ephemerides coming from the IMCCE or NASA/JPL.

• Installation
• Usage Documentation
• Precision
• Development
• Contributing
• License
• Code of Conduct

Install the gem and add to the application's Gemfile by executing:

$ bundle add astronoby

If Bundler is not being used to manage dependencies, install the gem by executing:

$ gem install astronoby

Since version 0.7.0, the usage documentation resides in the Wiki. For previous versions, you can access the documentation in the README for each release.

This library is still in heavy development. The public is not stable, please be aware new minor versions will probably lead to breaking changes until a major one is released.

Changes are documented in the CHANGELOG and adapting to breaking changes is described in the UPGRADING document.

The current precision for the major Solar System bodies' location in the sky as seen from an observer on Earth is below 10 arc seconds. It corresponds to half the size of Saturn when it is the closest to Earth.

While the precision is not enough for spacecraft navigation, it is enough for automated guiding of amateur telescopes.

The compared sources are: IMCCE, JPL Horizons, Stellarium, and the Skyfield library.

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and the created tag, and push the .gem file to rubygems.org.

The library is designed to be fast, but there is always room for improvement. When comparing the performance of two implementations, please use the performance benchmark in the console before and after your implementation.

$ bin/console

require_relative "benchmarks/performance"

PerformanceBenchmark.new.run

For fast feedback, you can customise the parameters:

PerformanceBenchmark
  .new(warmup_runs: 1, measure_runs: 3, iterations_per_run: 5)
  .run

Performance is not absolute, this is why the results are not documented here. What is important is to compare the relative performance of two implementations and make sure new features do not degrade the performance.

Please see CONTRIBUTING.md.

The gem is available as open source under the terms of the MIT License.

Everyone interacting in the Astronoby project's codebases, issue trackers, chat rooms and mailing lists are expected to follow the code of conduct.