Planisphere...a must have tool for star gazing

What is a planisphere..."...a star chart analog computing instrument in the form of two adjustable disks that rotate on a common pivot. It can be adjusted to display the visible stars for any time and date. It is an instrument to assist in learning how to recognize stars and constellations."

How to use...and how to make...

And from Bill Ashworth in the Linda Hall Library Newsletter...

Philippe La Hire, a French astronomer and mathematician, was born Mar. 18, 1640. In 1705, La Hire published two large celestial planispheres, or circular maps of the stars and constellations. The circumstances behind these maps are quite obscure. We don't know how La Hire compiled the data for the charts, and whether he had a role in designing the constellation figures. He well could have drawn them himself, since he was the son of a prominent artist, and trained as an artist as a young man. But the legend on the charts says they were "mis au jour," or "brought into the light," by Nicolas de Fer, as if they had been lying in some dark cupboard awaiting discovery. De Fer was a prominent engraver and cartographer, so he may have had a role he had in designing the charts—we just don’t know. But whatever their origin, they are gorgeous.

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Philippe de La Hire