How to make and use a planisphere

What this page covers: how to print, cut and pin the star wheel, how to set the date and time, and how accurate it is.

How to make a planisphere (print, cut, pin)

You need card stock (or paper glued to thin card), scissors, a craft knife, an awl and one paper fastener (brad).

Choose your place and paper. Print at 100% scale (Actual size).
Measure the 5 cm line. If it is shorter, the printer shrank the page.
Cut out the star wheel along its outer circle. Cut out the top disk and its gray window.
Keep the small center circle and the thin strip that holds it.
Pierce both + marks. Join the disks with the paper fastener, window on top.

How to use a planisphere (set the date and time)

Turn the star wheel until the date on its rim lines up with the time on the top disk. Use the evening’s date, even after midnight: at 2 AM after the evening of September 25, set September 25.

The hour ring shows standard time. During daylight saving time, set it 1 hour behind your clock: for 10 PM daylight time, set 9 PM.

Face a direction and hold the planisphere overhead, that direction’s letter at the bottom. The window shows the sky, and its edge is the horizon. The point straight overhead is off center, toward S (toward N in the Southern Hemisphere).

What latitude, longitude and time zone change

The window shape depends on latitude. Farther from the equator, the pole is higher and more stars never set.

The hour ring is turned for your longitude. Each degree east of your time zone’s central meridian (15° × the UTC offset) turns it 1°, about 4 minutes.

How it is drawn and how accurate it is

Projection: azimuthal equidistant, centered on the celestial pole.
Stars to magnitude 4.5 (or 5). Lines and names for 32 constellations. No Moon or planets.
Star positions are for J2000.0. The date ring uses the web planetarium’s sidereal time, averaged over 2026–2029.
Compared with the planetarium, star positions agree within 1° through 2050. Automated tests check 20 places, 20–65° north and south.
Atmospheric refraction is not included.

FAQ

Is this printable planisphere free?

Yes, with no sign-up. The page draws the sheets in your browser; print them or save a PDF from the print dialog.

How many years can I use a paper planisphere?

Star positions are for the year 2000 and stay within 1° through 2050. The Moon and planets are not drawn, so it works every year.

Why is my printed planisphere the wrong size?

Set the print scale to 100% (Actual size) and turn off Fit to page. The 5 cm line near the bottom of each sheet should measure 5 cm.

Does it work in the Southern Hemisphere?

Yes, from 20° to 65° south. The center is the south celestial pole, near the Southern Cross. The disks turn the other way, and there is no bright pole star.

Notes and your data

Your settings are saved only in this browser (localStorage, key hoshizora-sanpo_planisphere-en) and are never sent anywhere.
Knives and awls are sharp. Children should cut with an adult.
Stars: Yale Bright Star Catalogue, 5th ed., via brettonw/YaleBrightStarCatalog (MIT). Constellation lines and the Milky Way: Hoshizora Sanpo data (MIT). Star names: IAU WGSN.

Feedback form (Google Forms, in Japanese; you can write in English). We read every message but do not reply.