Definition of Celestial Planisphere

Planispheres are maps in which the celestial or terrestrial sphere is represented on a plane. Meanwhile, the planisphere Celestial is the one that represents the stars that are visible at a certain moment on a plane. It is generally used to be able to recognize stars and constellations.

Composition and how it works

It consists of two plausible adjusting discs that rotate on a common pivot. Just this movement It is the one that allows the visualization of the sky and therefore also of its objects of contemplation by excellence, which as we said are the stars, constellations, or any other cosmic element that is visible.

The celestial planisphere projects the celestial sphere onto a flat surface, a situation that may be subject to some inaccuracies. In the traditional versions of this planisphere, one of the discs offers us the representation of the horizon and shows us a division of the sky. Normally neither the horizon nor the stars can be seen clearly. This is so because the disk is made taking as a starting point a specific latitudinal point, a fact that is of course limiting. However, there are designs that allow you to interchange parts and other elements that offer greater detail.

This particularity of the celestial planisphere must be taken into account to know that in some cases the information we obtain from it may not be correct enough.

Conditions required to achieve accurate location data

Whenever we want to identify a star or constellation In particular, we must first control their position because they are in constant motion. As the planisphere brings us a cartographic representation, the info must always be compared to achieve reliable results.

Another issue that cannot be ignored is that the planisphere disk must be rotated to align time and day, always taking into account whether it is in summer or in winter, to also adjust this data in it. Once these conditions are met, it is possible to achieve an accurate representation of the stars at a given moment.

Antecedent: the astrolabe

The antecedent of this instrument is the astrolabe, a circumference graduated that has a needle on its axis that rotates pointing to the star that is being appreciated. On the edge of it there is a scale graduated in degrees and another that shows the minutes and hours. In its upper part there is a ring that suspends the instrument vertically in order to achieve the measurement.
It was about one tool widely used by astronomers, scientists and navigators to locate the stars and movements. Its creator would have been the Greek astronomer Claudius Ptolemy.

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