Round planisphere showing the constellations as mythological figures in full color. A planisphere is a portable device designed to aid in the study of stars and constellations visible in the night sky at any given date and time, generally for a particular locale. It consists of an outer rotating card with cutouts set against an inner hemispheric celestial map. The disk is rotated to match up the hour and minute of the day and compass points to printed data of day and month on the edge of the inner map, revealing the visible constellations within the cutout area. The disk is sometimes referred to by the antiquated word volvelle, used to describe rotating disks on various calculating devices.
An advertisement in a school trade catalog by McLees and Warren in 1876 promoted the Whitall planisphere as follows:
The Movable Planisphere is to Astronomy the same as a Map is to Geography, or to the clear sky what the Directory is to a City. It is the size of a 10-inch Celestial Globe, and as much better as it is cheaper. Of two kinds; one beautifully painted, the other as much like the sky as possible: Stars white on a deep blue-black ground. Both make a complete set. The two sent by mail on receipt of $6 or either for three dollars.
Whitall’s planispheres were designed for the observation of stars visible in a wide swath of North America centered on the latitude of Philadelphia. General instructions are printed on the front: “Bring the given hour and minute opposite the given day of the month; Hold the Zenith overhead with the Meridian in a line north and south. All the principal Stars visible in the United States will then appear within the Horizon.” The text on the back presents more detailed instructions and problems for students to solve.
Henry Whitall was a New York and Philadelphia publisher. Versions of his planispheres were published beginning in 1856 and were still being sold in a school supply catalogs in the later 19th century.
Full publication information: Henry Whitall, 512 Arch St., Philadelphia, Pennsylvania.
Condition: Generally very good with the usual overall light toning, wear, soiling, abrasions, warping. Varnished as issued.
Dekker, Elly, et al. Globes at Greenwich: A Catalogue of the Globes and Armillary Spheres in the National Maritime Museum, Greenwich. London: Oxford University Press and the National Maritime Museum, 1999. pp. 518-520.
Greenslade, Thomas B. Jr. "Planisphere of the Heavens." Instruments for Natural Philosophy, Kenyon College. http://physics.kenyon.edu/EarlyApparatus/Astronomy/Planisphere/Planisphere.html (20 December 2005).
Stott, Carole. Celestial Charts: Antique Maps of the Heavens. New York: Crescent Books, 1991. pp. 118-120.