Related Terms

 

Rising time

The moment when a body rises above the eastern horizon.

 

Setting time

The moment when a body sets below the western horizon.

 

Meridian

A line or arc starting from a point due north going up through one's zenith overhead, then down to the point of the horizon lying directly to one's south.

 

Meridian transit

The moment when a star lies on one's meridian, as it crosses from the eastern half of the sky into the west.

 

Circumpolar

A star or constellation which never sets below one's horizon is circumpolar. Two of the most famous and easily recognizable circumpolar constellations are Ursa Minor the Little Bear, which includes Polaris (the North Star); and Ursa Major the Big Bear, which contains the Big Dipper.

 

Culmination

For most stars, meridian transit is synonymous with culmination. However, circumpolar stars cross the meridian twice each day above the horizon, once above the north celestial pole, as they cross from east to west, and once beneath the north celestial pole, as they cross from west to east. Only the higher meridian transit of circumpolar stars is referred to as culmination.