polar_night {palinsol}

Begin and end of the polar night

Description

Provides the true solar longitude (in degrees) of the beginning and end of the polar night for a given latitude and orbit

Usage

polar_night(lat, orbit)

Arguments

lat

latitude

orbit

Output from a solution, such as ber78, ber90 or la04

Value

Either a message about the absence of polar night (for specified reasons), or the true solar longitude, in degrees, of the beginning and end of the polar night.

Author(s)

Michel Crucifix, U. catholique de Louvain, Belgium.

References

any standard text book of spherical astronomy

Examples

current_orbit <- la04(0)

# polar night at the equator ? 
polar_night (0, current_orbit)

# polar night at 80 N ? 
polar_night (80*pi/180, current_orbit)

# polar nights expressed as day of year 
l2day(current_orbit, polar_night (80*pi/180, current_orbit))