Astro - astronomy calculations (sunrise, sunset, moonrise, moonset, moon phase equinox, solstice, ...)

New version 0.2.0 is now out:

Enhancements

• Add Astro.equinox/2and Astro.solstice/2 to calculate solstices and equinoxes for a year. From these can be derived the seasons.

• Add Astro.Time.datetime_from_julian_days/1

• Add Astro.Time.utc_datetime_from_terrestrial_datetime/1

Now on to lunar calculations (phase, moonrise, moonset)… And to implement the Persian calendar (which is a Solar based calendar).

New version 0.3.0 is now out:

Change in behaviour

• Seconds are no longer truncated to zero when calculating datetimes and durations

Enhancements

• Add Astro.solar_noon/2 to return the true solar noon for a location and date

• Add Astro.hours_of_daylight/2 to return hours, minutes and seconds as a Time.t() representing the number of daylight hours for a give location and date

• Add Astro.sun_apparent_longitude/1 to return the apparent solar longitude on a given date. The result, a number of degrees between 0 and 360, can be used to determine the seasons.

This completes the work required to support the Persian calendar which will be landing on hex.pm in the next couple of days.

Astro version 0.5.0 is now out. The release adds functions that calculate the phase of the moon which, apart from anything else, is needed to calculate the Chinese calendar. Please note that Elixir 1.11 or later is required.

Bug Fixes

• Updates documentation to be clear about installation and setup requirements for tz_world

• Fixes test data for São Paulo now that it no longer uses DST

• Ensure :astro is started in test mode

Enhancements

This primary focus of this release is to add lunar calculations for moon phase.

• Adds Astro.date_time_new_moon_before/1

• Adds Astro.date_time_new_moon_at_or_after/1

• Adds Astro.lunar_phase_at/1

• Adds Astro.date_time_lunar_phase_at_or_before/2

• Adds Astro.date_time_lunar_phase_at_or_after/2

Astro version 0.6.0 is now out. This version avoids requiring some dependencies which makes the footprint smaller and compilation much faster. I have been using it to support the upcoming Chinese calendar with all tests passing so I consider the basic solar and lunar algorithms to be in solid shape.

Please note that Elixir 1.11 or later is required.

Roadmap

Roadmap to version 1.0 is to add Astro.moonrise/2 and Astro.moonset/2.

Additional development proposals or suggestions are very welcome.

Bug Fixes

• Fix Astro.Math.atan_r/2

• Fix Astro.Earth.ephemeris/1

Breaking changes

• Change Astro.Time.date_time_{from, to}_iso_days/1 to Astro.Time.date_time_{from, to}_moment/1

Enhancements

• Remove dependency on ex_cldr_calendar and jason

• Add Astro.sun_position_at/1 which is a public API for returning the right ascension, declination and radius (distance to the sun) at a given date/time.

• Add Astro.moon_position_at/1 which is a public API for returning the right ascension, declination and radius (distance to the moon) at a given date/time.

• Add Astro.illuminated_fraction_of_moon_at/1 to return the fraction of the moon that is lit at a given date/time.

A small update resulting in Astro version 0.9.0 that adds Astro.lunar_phase_emoji/1 to return the phase of the moon as an emoji. For example:

iex> Astro.lunar_phase_emoji 0
"🌑"
iex> Astro.lunar_phase_emoji 45
"🌒"
iex> Astro.lunar_phase_emoji 90
"🌓"
iex> Astro.lunar_phase_emoji 135
"🌔"
iex> Astro.lunar_phase_emoji 180
"🌕"
iex> Astro.lunar_phase_emoji 245
"🌖"
iex> Astro.lunar_phase_emoji 270
"🌗"
iex> Astro.lunar_phase_emoji 320
"🌘"
iex> Astro.lunar_phase_emoji 360
"🌑"

iex> ~U[2021-08-22 12:01:02.170362Z]
...> |> Astro.lunar_phase_at()
...> |> Astro.lunar_phase_emoji()
"🌕"

@habeebkhan, happy to help if I can but I’m not sure what you’re asking? Can you describe your use case for me?

Man, there are so many cool things built with Elixir.

I’ve released Astro 1.0 almost exactly a year after the last published version. This indicates API stability for existing functions (stable in most cases for at least 3 years). There is only one new function in this release:

Enhancements

• Release 1.0. This library was started four years ago and the public API has been stable for at least three of those years.

• Adds Astro.sun_azimuth_altitude/2. Thanks to @kimlai for the suggestion. Closes #3.

Nice lib! Is it possible to use it with tz instead of tzdata?

Edit: never mind, I should have checked the docs Astro — Astro v1.0.0

I’ve published Astro version 1.0.2. The primary fix is to calculate astronomical, nautical and civil sunrise/sunset correctly. The changelog entry is:

Bug Fixes

• Fix sunrise/sunset calculations when the solar elevation isn’t 90 degrees. Thanks to @cloud8421 for the issue. Closes #5.

Elixir 1.17 support

Astro compiles and runs without warnings on Elixir 1.17.

The difference between dawn and sunrise

There are four main daily milestones in the progress from darkness to light each day.

• Astronomical twilight is calculated when the geometric centre of the sun is 18 degrees below the horizon. This is the solar elevation where stars start to disappear agains the sky’s background. Therefore typically the time at which optical observation will stop.

• Nautical twilight is calculated when the geometric centre of the sun is 12 degrees below the horizon. This is the time at which the horizon can be observed by eye although it is not generally considered light enough for outdoor activity. The important of seeing the horizon is understandable for mariners.

• Civil twilight is what is generally considered to be dawn and is calculated when the geometric centre of the sun is 6 degrees below the horizon. This is the point at which outdoor activity is possible due to light from the sun below the horizon refracting in the atmosphere.

• Sunrise is calculated when the upper edge of the sun breaks the horizon, adapted to account for refraction of the suns rays.

Each of these - and indeed any arbitrary solar elevation - can be calculated in Astro by:

iex> Astro.sunrise(location, date, solar_elevation: :civil | :nautical | :astronomical | :geometric | angle_in_degrees)

Example

iex> london_z = %Geo.PointZ{coordinates: {-0.1276, 51.5072, 21.0}}
iex> Astro.sunrise(london_z, ~D[2024-05-26], solar_elevation: :civil)
DateTime.new(~D[2024-05-26], ~T[04:08:37.000000], "Europe/London")