PLANISPHERE

A 'planisphere' is a star chart analog computer that can be adjusted to display the night sky for any given latitude, time and date. The astrolabe is a predecessor of the modern planisphere.
It consists of a circular chart attached at its center to an opaque overlay that has a clear roundish window or hole. The chart is mounted so that it is free to rotate about the pivot point at the center. The border of the window (or cutout) represents the horizon. Since the night sky that one sees from the earth depends on the observer's latitude, planispheres themselves are printed for a range of latitudes and one should choose the latitude that is the closest match. Times are marked on the rims of the overlay (e.g., 10pm or 5am) and dates are marked rim of the starchart.
To use the planisphere, the overlay is rotated to match the time to the desired date. Any daylight saving time must be taken into account when setting the time. The stars currently visible in the sky that night at that time are then visible on the star chart through the window in the overlay. The overlay will also have a north indicator. Many users find it useful to hold the planisphere above their head with the north-indicator pointing towards true north. In this position, it is possible to imagine projecting the stars out onto the night sky. This allows quick identification of constellations and stars that are currently visible.
The stars in the opposite hemisphere of which, in absolute value, the declination is more than the colatitude for which the planisphere applies, are not on the chart, because they are always below the horizon (see culmination).
Since the planisphere is printed flat, there is considerable distortion, with lateral expansion in the outer parts of the full chart. For example, if the planisphere is for a northern latitude, the southern half of the hemisphere above the horizon covers more than half of the part of the chart visible through the hole. Southern areas of the sky are horizontally expanded.

Contents

List of Planispheres

List of Planispheres

★ Planisphere - high quality PDF format planisphere for the Northern Hemisphere. For best results, print with the scale set to 100% and the image rotated to fit a single page.

★ http://www.asahi-net.or.jp/~zs3t-tk/planisphere/planisphere.htm - free planisphere for the Northern and Southern Hemisphere by Toshimi Taki

★ http://members.ozemail.com.au/~starrylady/Planis1.htm - free planisphere for the Southern Hemisphere (30ºS to 35ºS latitude) by StarryLady Astronomy Services

★ Edmund Scientific

★ Miller Planisphere

★ The Night Sky

★ Firefly

★ Drehbare Himmelskarte - with 250 deep sky objects

★ Download a 'built it yourself' planisphere (in Hebrew)