Planisphere Facts

Planisphere Facts
A planisphere is an astronomical instrument used to display the location of stars. It is made of two adjustable disks that have a common pivot from which to rotate. The planisphere can help people to recognize stars and constellations of stars. The planisphere is believed to be derived from the astrolabe from Hellenistic astronomy. The Latin word for planisphere is planisphaerium. It was originally used to represent a spherical earth in the second century by the astronomer Ptolemy. It later went on to represent the star-filled celestial sphere. The first star chart with the name planisphere was created by Jacob Bartsch in 1624.
Interesting Planisphere Facts:
A planisphere can also be referred to as a star wheel. This tool is ideal for new star gazers by helping them understand the mechanics in the sky at night.
The planisphere represents the celestial sphere on a flat place which can be adjusted with the planisphere's pivot to see which stars are visible at a specific date and time.
The planisphere takes into consideration the movement of the earth and how it changes the location of a star or constellation based on the star gazer's location on earth.
The upper disc of a planisphere has a 'horizon' that highlights half of the night sky as that is all that one is able to see.
A planisphere can be designed with the polar azimuthal equidistant projection method, or the stereographic projection.
A planisphere has a circular star chart. It is overlaid with a circle with an elliptical hole that shows the sky visible at a given time and the stars or constellations that might be seen.
Planispheres for the northern and southern hemispheres are designed differently based on location.
Using a southern hemisphere planisphere in the northern hemisphere will not provide accurate data. The same is true if a northern hemisphere planisphere is used in the southern hemisphere.
Some planisphere models are designed to work in a specific latitude range which means they will lose accuracy of used elsewhere.
Some more expensive planispheres have interchangeable upper discs that allow the user to change based on their location. Some planispheres also have more horizon lines to use in different latitudes.
Planispheres considered more accurate are able to represent the declination and right ascension celestial coordinates. This allows users to look up the positions of planets and other objects that change position and find them in the night sky.
A planisphere can be considered to be a type of analog computer used for locating stars in the sky.
NASA has a set of star wheels, or planispheres, called the Kepler Star Wheels. They can be printed out and used from either the northern hemisphere or southern hemisphere. The name Kepler originated from Johannes Kepler, an astronomer and astrologer considered to be a key figure in the scientific revolution in the 1600s.
It is possible to make a planisphere at home by printing out the discs and assembling them.
There is always distortion when using a planisphere as it portrays the celestial sphere as flat.

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