✨ Caelus • Credits

Astronomical data

Every position, time and diagram on this site is computed from the following sources.

INPOP19a

Planetary and lunar ephemeris computed by the IMCCE at the Paris Observatory. Caelus embeds INPOP19a segments to place the Sun, the Moon and the planets. The IMCCE distributes INPOP freely for scientific use and asks that it be cited.

IERS Earth orientation data

Earth orientation parameters published by the International Earth Rotation and Reference Systems Service. They give the small, irregular variations in the Earth's rotation that accurate rise and set times depend on. Caelus refreshes them daily.

Clementine albedo mosaic - Public domain

Albedo mosaic assembled from images taken by the Clementine mission (NASA/USGS). The maria and highlands drawn on the lunar disc are traced from it.

List of Messier objects - CC BY-SA 4.0

Names, types, magnitudes, apparent sizes and distances of the Messier objects listed in the deep sky sections.

New General Catalogue - CC BY-SA 4.0

The same for the NGC objects listed alongside them.

Software

The stack Caelus runs on. The complete list of dependencies, direct and indirect, is in the Gemfile.

Astronoby - MIT

Every astronomical calculation on this site: positions, rise and set times, phases, eclipses, conjunctions. Caelus exists largely to show what Astronoby can do.

Ruby Ephem - MIT

Reads the binary SPK ephemeris files Astronoby computes from.

IERS - MIT

Downloads and parses the Earth orientation bulletins.

Ruby - Ruby licence

The language Caelus is written in.

Ruby on Rails - MIT

The web framework.

Hotwire - MIT

Turbo and Stimulus, behind the page updates and the small amount of JavaScript.

ViewComponent - MIT

Renders the charts and diagrams.

Tailwind CSS - MIT

The styles.

Propshaft - MIT

Serves the assets.

Importmap for Rails - MIT

Ships the JavaScript without a bundler.

Solid Queue - MIT

Runs the background jobs that generate celestial events.

Solid Cache - MIT

Caches computed astronomical data.

Solid Cable - MIT

Part of the Rails default stack, backing Action Cable.

SQLite - Public domain

Stores the celestial events, the cache and the job queue.

Puma - BSD-3-Clause

The application server.

Thruster - MIT

Sits in front of Puma for TLS and asset caching.

Rack::Attack - MIT

Rate limiting.

Kamal - MIT

Deploys Caelus to its server.

RSpec - MIT

The test suite.

Standard - MIT

Formats and lints the Ruby and JavaScript.

Services

The third-party services involved in running Caelus. None of them is used for advertising or profiling. See the Privacy Policy for what leaves your browser.

AppSignal

Application monitoring: errors, performance and anonymous usage counters.

GoatCounter

Cookieless page-view counting.

Caelus

Caelus is released under the MIT licence and written by Rémy Hannequin.

Contributions and feedback are welcome on the source repository.