Astro v0.1.0 Astro View Source

Functions for basic astronomical observations such as sunrise, sunset, solstice, equinox, moonrise, moonset and moon phase.

Link to this section Summary

Functions

Calculates the sunrise for a given location and date.

Calculates the sunset for a given location and date.

Link to this section Types

Link to this section Functions

Link to this function

sunrise(location, date, options \\ default_options())

View Source
sunrise(location(), date(), options()) ::
  {:ok, DateTime.t()} | {:error, :time_zone_not_found | :no_time}

Calculates the sunrise for a given location and date.

Sunrise is the moment when the upper limb of the sun appears on the horizon in the morning.

Arguments

  • location is the latitude, longitude and optionally elevation for the desired sunrise time. It can be expressed as:

    • {lng, lat} - a tuple with longitude and latitude as floating point numbers. Note the order of the arguments.
    • a Geo.Point.t struct to represent a location without elevation
    • a Geo.PointZ.t struct to represent a location and elevation
  • date is a Date.t, NaiveDateTime.t or DateTime.t to indicate the date of the year in which the sunrise time is required.

  • options is a keyword list of options.

Options

  • solar_elevation represents the type of sunrise required. The default is :geometric which equates to a solar elevation of 90°. In this case the calulation also accounts for refraction and elevation to return a result which accords with the eyes perception. Other solar elevations are:

    • :civil representing a solar elevation of 96.0°. At this point the sun is just below the horizon so there is generally enough natural light to carry out most outdoor activities.

    • :nautical representing a solar elevation of 102.0° This is the point at which the horizon is just barely visible and the moon and stars can still be used for navigation.

    • :astronomicalrepresenting a solar elevation of 108.0°. This is the point beyond which astronomical observation becomes impractical.

    • Any floating point number representing the desired solar elevation.

  • :time_zone is the time zone to in which the sunrise is requested. The default is :default in which the sunrise time is reported in the time zone of the requested location. Any other time zone name supported by the option :time_zone_database is acceptabe.

  • :time_zone_database represents the module that implements the Calendar.TimeZoneDatabase behaviour. The default is Tzdata.TimeZoneDatabase.

Returns

  • a DateTime.t representing the time of sunrise in the requested timzone at the requested location or

  • {:error, :time_zone_not_found} if the requested time zone is unknown

  • {:error, :no_time} if for the requested date and location there is no sunrise. This can occur at very high latitudes during summer and winter.

Examples

  # Sunrise in Sydney, Australia
  Astro.sunrise({151.20666584, -33.8559799094}, ~D[2019-12-04])
  {:ok, #DateTime<2019-12-04 05:37:00.000000+11:00 AEDT Australia/Sydney>}

  # Sunrise in Alert, Nanavut, Canada
  Astro.sunrise({-62.3481, 82.5018}, ~D[2019-12-04])
  {:error, :no_time}
Link to this function

sunset(location, date, options \\ default_options())

View Source
sunset(location(), date(), options()) ::
  {:ok, DateTime.t()} | {:error, :time_zone_not_found | :no_time}

Calculates the sunset for a given location and date.

Sunset is the moment when the upper limb of the sun disappears below the horizon in the evening.

Arguments

  • location is the latitude, longitude and optionally elevation for the desired sunrise time. It can be expressed as:

    • {lng, lat} - a tuple with longitude and latitude as floating point numbers. Note the order of the arguments.
    • a Geo.Point.t struct to represent a location without elevation
    • a Geo.PointZ.t struct to represent a location and elevation
  • date is a Date.t, NaiveDateTime.t or DateTime.t to indicate the date of the year in which the sunset time is required.

  • options is a keyword list of options.

Options

  • solar_elevation represents the type of sunset required. The default is :geometric which equates to a solar elevation of 90°. In this case the calulation also accounts for refraction and elevation to return a result which accords with the eyes perception. Other solar elevations are:

    • :civil representing a solar elevation of 96.0°. At this point the sun is just below the horizon so there is generally enough natural light to carry out most outdoor activities.

    • :nautical representing a solar elevation of 102.0° This is the point at which the horizon is just barely visible and the moon and stars can still be used for navigation.

    • :astronomicalrepresenting a solar elevation of 108.0°. This is the point beyond which astronomical observation becomes impractical.

    • Any floating point number representing the desired solar elevation.

  • :time_zone is the time zone to in which the sunset is requested. The default is :default in which the sunset time is reported in the time zone of the requested location. Any other time zone name supported by the option :time_zone_database is acceptabe.

  • :time_zone_database represents the module that implements the Calendar.TimeZoneDatabase behaviour. The default is Tzdata.TimeZoneDatabase.

Returns

  • a DateTime.t representing the time of sunset in the requested time zone at the requested location or

  • {:error, :time_zone_not_found} if the requested time zone is unknown

  • {:error, :no_time} if for the requested date and location there is no sunset. This can occur at very high latitudes during summer and winter.

Examples

  # Sunset in Sydney, Australia
  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 Alert, Nanavut, Canada
  Astro.sunset({-62.3481, 82.5018}, ~D[2019-12-04])
  {:error, :no_time}