Add #phase_angle and #illuminated_fraction to planets#200
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rhannequin merged 2 commits intomainfrom Aug 9, 2025
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While generally mostly interesting for the Moon, the phase angle and illuminated fraction are two figures that can be useful for anticipating how a planet looks like. This is particularly the case for Mercury and Venus. As inferior planets (with orbits closer to the Sun than the Earth), they are never observed fully illuminated and always show a phase. For superior planets, the information is less interesting as we constantly see them almost completely illuminated. But still, the information is there. Because the phase angle depends on the vector between the sun and the observer, the sun needs to be computed for each planet instance. This isn't great, however the new feature of caching should help.
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## 0.8.0 - 2025-09-01 _If you are upgrading: please see [UPGRADING.md]._ ### Bug fixes * Fix UPGRADING documentation ([#178]) * Fix possible division by zero in RTS ([#185]) ### Features * Introduce performance benchmark ([#183]) * Cache positions in RTS calculator ([#182]) * Internal global LRU cache ([#186]) * Global configuration ([#187]) * Compute the constellation a body is in ([#199]) * Add `#phase_angle` and `#illuminated_fraction` to planets ([#200]) * Apparent magnitude ([#201]) * Add #events_between to TwilightCalculator with better accuracy ([#204]) * `#angular_diameter` on Solar System bodies ([#207]) * Fix constellation boundaries near 24h right ascension ([#209]) ### Improvements * Bump standard from 1.49.0 to 1.50.0 by @dependabot ([#177]) * Bump ephem from 0.3.0 to 0.4.1 by @dependabot ([#181], [#191]) * Bump irb from 1.14.3 to 1.15.2 by @dependabot ([#184]) * Bump rspec from 3.13.0 to 3.13.1 by @dependabot ([#188]) * Bump benchmark from 0.4.0 to 0.4.1 by @dependabot ([#189]) * Bump rake from 13.2.1 to 13.3.0 by @dependabot ([#190]) * Bump matrix from 0.4.2 to 0.4.3 by @dependabot ([#193]) * Update rubyzip requirement from ~> 2.3 to ~> 3.0 by @dependabot ([#194]) * Bump rubyzip from 3.0.0 to 3.0.2 by @dependabot ([#202], [#206]) * Exclude benchmarks from release ([#196]) * `Epoch` refactoring into `JulianDate` ([#197]) * Support Ruby 3.4.4 ([#198]) * Bump actions/checkout from 4 to 5 ([#203]) * Internal documentation ([#205]) ### Backward-incompatible changes * `Epoch` refactoring into `JulianDate` ([#197]) * `#angular_diameter` on Solar System bodies ([#207]) * Rename "epoch" ([#208]) ### Closed issues * Consider adding typical usage/deployment info ([#179]) * Performance degradation in v0.7 ([#180]) **Full Changelog**: v0.7.0...v0.8.0 [#177]: #177 [#178]: #178 [#179]: #179 [#180]: #180 [#181]: #181 [#182]: #182 [#183]: #183 [#184]: #184 [#185]: #185 [#186]: #186 [#187]: #187 [#188]: #188 [#189]: #189 [#190]: #190 [#191]: #191 [#193]: #193 [#194]: #194 [#196]: #196 [#197]: #197 [#198]: #198 [#199]: #199 [#200]: #200 [#201]: #201 [#202]: #202 [#203]: #203 [#204]: #204 [#205]: #205 [#206]: #206 [#207]: #207 [#208]: #208 [#209]: #209 [UPGRADING.md]: https://github.com/rhannequin/astronoby/blob/main/UPGRADING.md
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While generally mostly interesting for the Moon, the phase angle and illuminated fraction are two figures that can be useful for anticipating how a planet looks like.
This is particularly the case for Mercury and Venus. As inferior planets (with orbits closer to the Sun than the Earth), they are never observed fully illuminated and always show a phase.
For superior planets, the information is less interesting as we constantly see them almost completely illuminated. But still, the information is there.
Because the phase angle depends on the vector between the sun and the observer, the sun needs to be computed for each planet instance. This isn't great, however the new feature of caching should help.
#phase_anglereturns anAstronoby::Angleobject,#illuminated_fractionreturns aFloat.Because the phase angle depends on the Sun, because in Astronoby an apparent position is geocentric, is doesn't make sense for
Astronoby::SunandAstronoby::Earthto have values for these two methods. Therefore, both classes returnnilfor both methods.Values have been compared with the IMCCE, JPL Horizons and Skyfield.