Please say hi to a new lib, Astro that aims to deliver easy-to-consume astronomy calculations of practical use. For now it only calculates sunrise and sunset. In testing its precision is within 1 minute of the results returns from DateAndTime.com.
It makes use of tz_world to dereference geo coordinates to a timezone and tzdata for time zone conversions.
This lib started our as a requirement to support certain solar, lunar and lunisolar calendars but it has wider applicability.
Examples
# Sunrise in Sydney on December 4th
iex> Astro.sunrise({151.20666584, -33.8559799094}, ~D[2019-12-04])
{:ok, #DateTime<2019-12-04 05:37:00.000000+11:00 AEDT Australia/Sydney>}
# Sunset in Sydney on December 4th
iex> Astro.sunset({151.20666584, -33.8559799094}, ~D[2019-12-04])
{:ok, #DateTime<2019-12-04 19:53:00.000000+11:00 AEDT Australia/Sydney>}
# Sunset in the town of Alert in Nunavut, Canada
# ...doesn't exist since there is no sunset in summer
iex> Astro.sunset({-62.3481, 82.5018}, ~D[2019-07-01])
{:error, :no_time}
# ...or sunrise in winter
iex> Astro.sunrise({-62.3481, 82.5018}, ~D[2019-12-04])
{:error, :no_time}
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 SΓ£o 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.
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.
Iβve 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.