It is the angular distance of any point from the equator, measured north or south, along the earth’s curved surfaced equaling the angle between the respective horizontal planes. It is measured in degrees, minutes, and seconds, each minute equaling one sea-mil in length.


It is the angle between the terrestrial meridian drawn from the pole, through a place, and a standard meridian now taken at Greenwich. All determination of longitude are based on the earth turning through 360 in 24 hours, or the sun reaching 15 west each hour.


Imaginary circle in sky passing through celestial poles.

Perihelion and Aphelion

Point in orbit of planet is called Perihelion, whereas the point of planet’s orbit farthest the sun is called Aphelion.