Despite the leaps and bounds in stargazing smartphone apps and astronomy tech, planispheres remain one of the amateur astronomer’s most reliable tools.
Author and planisphere collector Peter Grimwood presents a history of these night-sky navigators in pictures, with a selection of examples taken from the 200 that make up his new book Card Planispheres: A Collector’s Guide.
A planisphere is a map of part of the celestial sphere that can be adjusted to match the positions of the stars in the night sky for a particular time and location.
Initially developed around 200 BC as the metallic ‘planispheric astrolabe’, the modern-day planisphere is usually made of card or plastic discs with a rotating oval 'horizon' to reveal the stars visible overhead.
You simply turn the top rotating disc to match the direction you’re facing with the current date and - lo and behold - you get a map of the constellations and asterisms in the sky above.
The basic idea has been around for centuries and, depending who you believe, was invented by Eudoxus of Cnidus (a Greek mathematician), Hypatia (a Greek astronomer) or Vitruvius (a Roman architect and engineer).
Here's a selection of some of my personal favourites, showing how this simple but effective design has been adopted for astronomers in different regions of the world.
(All images are copyright Peter Grimwood)
A big one from the USA at around 15.5 inches square, this one was made in 1866 by Henry Whitall. He made both round and square planispheres with either stars on a dark blue background, or (like this one) a background featuring the mythical constellation figures.
This one is Argentinean and printed in Spanish. It has a southern hemisphere starmap on one side (aperture for 35oS for Buenos Aires) and a Northern Hemisphere starmap on the other (45oN for Madrid). It dates from around 1960.
A Swiss "Zodiac" planisphere made in 1946. Also double sided, but this time both sides are for the northern hemisphere. One is the view to the north, the other the view to the south. This is clever way of reducing the distortion of the constellations being projected on a flat sheet.
The 1985/6 return of Halley's comet was only really visible in the southern hemisphere, and here is a planisphere that includes the track of the comet with dates overprinted on the star field. It was printed by Astroprom Australia Pty Ltd.
Here’s another big one from the US. Hammond’s Improved Planisphere is 16 inches square and was produced around 1925. It has the unusual feature of a horizon aperture that can be adjusted for a range of latitudes.
Printed in 1837 by London globe and map makers George and John Cary, this 15-inch square planisphere has both a rotating starmap and a rotating horizon aperture.
Horizon apertures vary according to the latitude of the observer. This 1925 planisphere produced in Ceylon (now Sri Lanka) has the semicircular cut-out needed for use on the equator.
The UK-based company of George Philip and Sons produced this combination planisphere and orrery in 1914. Rather basic, the two arms had movable buttons to show the position of the Sun and one other planet.
Showing the nearly circular horizon aperture for 65oN, this planisphere is designed for use in Sweden, Norway and Finland.
Virtually unchanged in design from 1906 to 1960, this 15-inch square 'Star and Planet Finder' has a thick starmap that is designed to have a set of planet pins stuck into the plane of the ecliptic, their positions given by planet tables supplied with the planisphere.
