Circumpolar Star or Constellation is a constellation or star that never falls below the horizon and can been seen all the time from either the northern or southern hemisphere. These stars are located near the celestial pole. They circle the celestial pole which is where their name comes from.
In the northern hemisphere, the northern celestial pole star is Polaris. In the southern hemisphere, the closest to the equivalent of Polaris is Sigma Octantis which is also known as Polaris Australis. Polaris Australis is a very dim star and nearly beyond the bounds of eye sight.
The more north you are, the more circumpolar stars/constellations there are. If you were in Tromso, Norway, your Circumpolar stars would be the Polar Star and the stars that make up. The further south you go from Tromso, the less constellations / stars that are always viewable.
If you move to London, the constellation Leo Minor is no longer visible all the time and therefore no longer circumpolar. You are still able to see Ursa Minor, Ursa Major, Cassiopeia and Draco for example all year round.
If you look up at the sky from Miami, the only circumpolar constellation that you are able to see all year round is Ursa Minor with Ursa Major only visible for the first eight months of the year at 9p.m.
In the days long ago, before Satnav, explorers would use the stars to navigate. Polaris was one of the most important because in the northern hemisphere, it was always visible. Being always visible, people were able to tell which direction they were going in.
Being on the Equator such as being in Quito, the capital of Ecuador, there are no Circumpolar stars. The nearest circumpolar constellation is Octans. Whilst part of the constellation boundaries is in view all year round, the main stars are not.
The main circumpolar constellations include Apus, Chameleon, Octans, Mensa and Hydrus to name a few. It really does depend on how far south you go. At the south pole, circumpolar constellations include Scorpius and Sagittarius but because of the tilt of the Sun, you won't be able to see them as they will be blocked out by the twenty hours of sun-light.
If you trek north from the South Pole, the number of circumpolar stars and constellations will decrease until the last circumpolar constellation left to be seen is Octans because it is below or above the south pole, depending on how you see it.
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