Planisphere

Specifications

Observing parameters

Overview

A planisphere is a rotating star disc under a cut-out window. Line up the date and time and the window shows exactly which constellations are above your horizon at that moment, with east and west marked. No batteries, no screen, no updates.

It is a planning tool rather than a finding tool: it tells you what is up and where roughly to look, but not how to get to a specific faint galaxy. Pair it with a detailed atlas for the hop. The one critical purchase detail is latitude — a planisphere is printed for a range of latitudes, and an out-of-range one will show objects that never rise at your site.

For a beginner it is the fastest way to build a mental map of the seasonal sky, and it remains useful to experienced observers for checking rise and set times at a glance.

Where it fits

Practical notes

• Buy the planisphere printed for your latitude band — this is the one specification that cannot be fudged.
• Remember to add an hour if you are on daylight saving time.
• Use it at dusk to plan the night rather than mid-session, when a red light is needed anyway.
• Pair with a detailed atlas: planisphere for "what", atlas for "how to get there".

Pairs with

• Star Atlas
• Red Flashlight
• Finderscope
• Observing Chair