Astronoby

Ruby library to provide a useful API to compute astronomical calculations, based on astrometry books.

The main reference is:

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

Content

Installation
Usage
- Angle manipulation
- Coordinates conversion
- Sun
  - Sun's location in the sky
  - Sunrise and sunset times and azimuths
  - Twilight times
- Solstice and Equinox times
- Moon
  - Moon's location in the sky
  - Moon's current attributes
  - Moon's phases of the month
  - Moonrise and moonset times and azimuths
Precision
Development
Contributing
License
Code of Conduct

Installation

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

Usage

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.

Angle manipulation

angle1 = Astronoby::Angle.from_degrees(90)
angle2 = Astronoby::Angle.from_radians(Math::PI / 2)
angle3 = Astronoby::Angle.from_hours(12)

angle1 == angle2
# => true

angle1 < angle3
# => true

angle = angle1 + angle2 + angle3
angle.cos
# => 1.0

Distance manipulation

distance1 = Astronoby::Distance.from_astronomical_units(1)
distance2 = Astronoby::Distance.from_kilometers(149_597_870.7)
distance3 = Astronoby::Distance.from_meters(300)

distance1 == distance2
# => true

distance1 > distance3
# => true

distance =
  Astronoby::Distance.from_m(300) +
  Astronoby::Distance.from_km(3)

distance.km
# => 3.3

Coordinates conversion

observer = Astronoby::Observer.new(
  latitude: Astronoby::Angle.from_degrees(38),
  longitude: Astronoby::Angle.from_degrees(-78)
)

equatorial = Astronoby::Coordinates::Equatorial.new(
  right_ascension: Astronoby::Angle.from_hms(17, 43, 54),
  declination: Astronoby::Angle.from_dms(-22, 10, 0)
)

horizontal = equatorial.to_horizontal(
  time: Time.new(2016, 1, 21, 21, 30, 0, "-05:00"),
  observer: observer
)

horizontal.altitude.str(:dms)
# => "-73° 27′ 19.1557″"

horizontal.azimuth.str(:dms)
# => "+341° 33′ 21.587″"

Sun

Sun's location in the sky

time = Time.utc(2023, 2, 17, 11, 0, 0)

observer = Astronoby::Observer.new(
  latitude: Astronoby::Angle.from_degrees(48.8566),
  longitude: Astronoby::Angle.from_degrees(2.3522)
)

sun = Astronoby::Sun.new(time: time)

horizontal_coordinates = sun.horizontal_coordinates(
  observer: observer
)

horizontal_coordinates.altitude.degrees
# => 27.500082409271247

horizontal_coordinates.altitude.str(:dms)
# => "+27° 30′ 0.2966″"

Sunrise and sunset times and azimuths

Only date part of the time is relevant for the calculation. The offset must be provided to the observer.

utc_offset = "-05:00"
time = Time.new(2015, 2, 5, 0, 0, 0, utc_offset)
observer = Astronoby::Observer.new(
  latitude: Astronoby::Angle.from_degrees(38),
  longitude: Astronoby::Angle.from_degrees(-78),
  utc_offset: utc_offset
)
sun = Astronoby::Sun.new(time: time)
observation_events = sun.observation_events(observer: observer)

observation_events.rising_time.getlocal(utc_offset)
# => 2015-02-05 07:12:59 -0500

observation_events.rising_azimuth.str(:dms)
# => "+109° 29′ 34.3674″"

observation_events.transit_time.getlocal(utc_offset)
# => 2015-02-05 12:25:59 -0500

observation_events.transit_altitude.str(:dms)
# => "+36° 8′ 15.8197″"

observation_events.setting_time.getlocal(utc_offset)
# => 2015-02-05 17:39:27 -0500

observation_events.setting_azimuth.str(:dms)
# => "+250° 40′ 42.8609″"

Twilight times

time = Time.new(2024, 1, 1)
sun = Astronoby::Sun.new(time: time)
observer = Astronoby::Observer.new(
  latitude: Astronoby::Angle.from_degrees(48.8566),
  longitude: Astronoby::Angle.from_degrees(2.3522)
)
twilight_events = sun.twilight_events(observer: observer)

twilight_events.morning_astronomical_twilight_time
# => 2024-01-01 05:49:25 UTC

twilight_events.morning_nautical_twilight_time
# => 2024-01-01 06:27:42 UTC

twilight_events.morning_civil_twilight_time
# => 2024-01-01 07:07:50 UTC

twilight_events.evening_civil_twilight_time
# => 2024-01-01 16:40:01 UTC

twilight_events.evening_nautical_twilight_time
# => 2024-01-01 17:20:10 UTC

twilight_events.evening_astronomical_twilight_time
# => 2024-01-01 17:58:26 UTC

Solstice and Equinox times

year = 2024

Astronoby::EquinoxSolstice.march_equinox(year)
# => 2024-03-20 03:05:08 UTC

Astronoby::EquinoxSolstice.june_solstice(year)
# => 2024-06-20 20:50:18 UTC

Moon

Moon's location in the sky

time = Time.utc(2023, 2, 17, 11, 0, 0)

observer = Astronoby::Observer.new(
  latitude: Astronoby::Angle.from_degrees(48.8566),
  longitude: Astronoby::Angle.from_degrees(2.3522)
)

moon = Astronoby::Moon.new(time: time)

horizontal_coordinates = moon.horizontal_coordinates(
  observer: observer
)

horizontal_coordinates.altitude.degrees
# => 10.277834691708053

horizontal_coordinates.altitude.str(:dms)
# => "+10° 16′ 40.2048″"

Moon's current attributes

time = Time.utc(2024, 6, 1, 10, 0, 0)
moon = Astronoby::Moon.new(time: time)

moon.illuminated_fraction.round(2)
# => 0.31

moon.distance.km.round
# => 368409

moon.phase_angle.degrees.round
# => 112

Moon's phases of the month

june_phases = Astronoby::Moon.monthly_phase_events(
  year: 2024,
  month: 6
)

june_phases.each { puts "#{_1.phase}: #{_1.time}" }
# new_moon: 2024-06-06 12:37:41 UTC
# first_quarter: 2024-06-14 05:18:28 UTC
# full_moon: 2024-06-22 01:07:53 UTC
# last_quarter: 2024-06-28 21:53:25 UTC

Moonrise and moonset times and azimuths

Only date part of the time is relevant for the calculation. The offset must be provided to the observer.

utc_offset = "-10:00"
time = Time.new(2024, 9, 1, 0, 0, 0, utc_offset)
observer = Astronoby::Observer.new(
  latitude: Astronoby::Angle.from_degrees(-17.5325),
  longitude: Astronoby::Angle.from_degrees(-149.5677),
  utc_offset: utc_offset
)
moon = Astronoby::Moon.new(time: time)
observation_events = moon.observation_events(observer: observer)

observation_events.rising_time.getlocal(utc_offset)
# => 2024-09-01 05:24:57 -1000

observation_events.rising_azimuth.str(:dms)
# => "+93° 7′ 43.2347″"

observation_events.transit_time.getlocal(utc_offset)
# => 2024-09-01 11:12:34 -1000

observation_events.transit_altitude.str(:dms)
# => "+26° 59′ 30.9915″"

observation_events.setting_time.getlocal(utc_offset)
# => 2024-09-01 16:12:10 -1000

observation_events.setting_azimuth.str(:dms)
# => "+273° 29′ 30.0954″"

Precision

The current precision for the Sun's apparent location in the sky, compared to values computed by the IMCCE is approximately 1 arc minute. It corresponds to twice the apparent size of Jupiter when it is the closest to Earth.

While the precision is not enough for very high accuracy computations, it is equal to the Human naked eye's angular resolution.

Development

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.

Contributing

Please see CONTRIBUTING.md.

License

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

Code of Conduct

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

astronoby

Development

Runtime

Astronoby

Content

Installation

Usage

Angle manipulation

Distance manipulation

Coordinates conversion

Sun

Sun's location in the sky

Sunrise and sunset times and azimuths

Twilight times

Solstice and Equinox times

Moon

Moon's location in the sky

Moon's current attributes

Moon's phases of the month

Moonrise and moonset times and azimuths

Precision

Development

Contributing

License

Code of Conduct