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You may know sunset/sunrise beside storm notification was aksed by almost all the Ambit users from Suunto. Now Sunnto planned to add the features in Ambit2 and we hope to have it in Ambit classic as well. Here I will put information on how sunset/sunrise will claculated regarding to GPS information and local time. All hail to writer on Wiki.

Sunrise equation - Wikipedia, the free encyclopedia

May be a little complicated but if suunto adds some complex function like sunus (sin(X)) to movescount we may even write our own sunset/sunrise app.

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**SUNSET/SUNRISE Equation:**

The Earth rotates at an angular velocity of 15°/hour, therefore the expression

The sign convention is typically that the observer latitude

The expression above is always applicable for latitudes between the Arctic circle and Antarctic circle. North of the Arctic circle or south of the Antarctic circle, there is at least one day of the year with no sunrise or sunset. Formally, there is a sunrise or sunset when

Generalized Equation

Generalized Equation

Also note that the above equation neglects the influence of atmospheric refraction (which lifts the solar disc by approximately 0.6° when it is on the horizon) and the non-zero angle subtended by the solar disc (about 0.5°). The times of the rising and the setting of the upper solar limb as given in astronomical almanacs correct for this by using the more general equation

with the altitude (a) of the center of the solar disc set to about −0.83° (or −50 arcminutes).

**Complete calculation on Earth**

The generalized equation relies on a number of other variables which need to be calculated before it can itself be calculated. These equations have the solar-earth constants substituted with angular constants expressed in degrees.

Calculate current Julian Cycle

Calculate current Julian Cycle

where:

**[edit]Approximate Solar Noon**

Solar Mean Anomaly

Solar Mean Anomaly

M is the solar Mean Anomaly.

Equation of Center

Equation of Center

C is the Equation of the center.

Ecliptic Longitude

Ecliptic Longitude

λ is the ecliptic longitude.

Solar Transit

Solar Transit

J[SUB]transit[/SUB] is the hour angle for solar transit (or solar noon).

Declination of the Sun

Declination of the Sun

δ is the declination of the sun.

Hour Angle

Hour Angle

*This is the equation from above with corrections for astronomical refraction and solar disc diameter.*

where:

ω[SUB]o[/SUB] is the hour angle;

This is the main equation from above with the solar disc correction.

For observations on a sea horizon an elevation-of-observer correction, add

Calculate Sunrise and Sunset

Calculate Sunrise and Sunset

J[SUB]set[/SUB] is the actual Julian Date of sunset;

J[SUB]rise[/SUB] is the actual Julian Date of sunrise.

Sunrise equation - Wikipedia, the free encyclopedia