Planisphere
A planisphere is rotating star chart that shows well-known stars and constellations in the sky for a specific date and time...
A planisphere is a rotating star chart designed to show the positions of stars and constellations in the night sky for any chosen date and time. It consists of two main parts: rotating circular star map and a stationary front plate with a window that represents the visible portion of the sky. By aligning the date and time scales, the user can quickly determine which well-known stars and constellations should be visible at that moment. In this sense, a planisphere functions like a simple analog computer. It models mechanically the daily and seasonal motion of the sky caused by Earth’s rotation and orbit.
The design of a planisphere (positioning of a small window in a front plate) depends on the observer’s geographic latitude. Because the appearance of the sky changes with latitude, a planisphere made for one region will not accurately represent the sky from a very different location. As a result, planispheres are typically labeled for specific latitude ranges, such as 40°–50° north. Planispheres are generally made of paper, but in the image below you can see a planisphere made from laser-cut basswood (link is provided below). When ordering it, the observer's precise geographical location is taken into account.
