Documentation
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Overview ¶
Package solar provides a thin wrapper around github.com/mstephenholl/go-solar for computing sunrise/sunset and determining whether a given UTC instant is during daytime or nighttime.
The wrapper preserves the historical API used throughout this repository (Calculate, SunTimes, IsNight) while delegating the underlying astronomical math to go-solar.
Index ¶
Constants ¶
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Variables ¶
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Functions ¶
Types ¶
type SunTimes ¶
SunTimes holds sunrise and sunset times for a given date and location.
func Calculate ¶
Calculate computes sunrise and sunset UTC times for a given date, latitude, and longitude. Computation is delegated to github.com/mstephenholl/go-solar.
Edge cases:
- Polar night (sun never rises): both Sunrise and Sunset are set to the start of the UTC day, so any time on that day is considered "night".
- Midnight sun (sun never sets): Sunrise is set to the start of the UTC day and Sunset to 23:59:59 UTC, so any time on that day is considered "day".
type TwilightTimes ¶ added in v1.2.2
type TwilightTimes struct {
Dawn time.Time // beginning of morning civil twilight (sun at -6° rising)
Dusk time.Time // end of evening civil twilight (sun at -6° setting)
}
TwilightTimes holds the morning (Dawn) and evening (Dusk) civil twilight boundaries for a given UTC date and location. Per ICAO Annex 2 / EU Regulation 2018/1976 the aeronautical definition of "night" is:
"the period between the end of evening civil twilight and the beginning of morning civil twilight or such other period between sunset and sunrise as may be prescribed by the appropriate authority."
Civil twilight is defined as the period during which the centre of the sun is between 0° and 6° below the horizon. Dawn marks the beginning of morning civil twilight; Dusk marks the end of evening civil twilight.
func CivilTwilight ¶ added in v1.2.2
func CivilTwilight(date time.Time, latitude, longitude float64) TwilightTimes
CivilTwilight computes the morning-civil-twilight start (Dawn) and evening-civil-twilight end (Dusk) in UTC for the given date and location. These are the EASA "night" boundaries: any time between Dusk and the next day's Dawn is considered night.
Edge cases (polar night / midnight sun): when the sun is permanently below or above the civil-twilight threshold, go-solar returns the zero time for the affected boundary. We collapse those zero values to the start of the UTC day for Dawn and end of the UTC day for Dusk so that:
- permanent polar night (no civil dawn or dusk): the entire UTC day is night;
- midnight sun (sun stays above −6°): the entire UTC day is day.
Source Files