An astrolabe is an elaborate instrument which combines a mechanical model of the sky’s rotation through the night – similar to a modern planisphere – with an observing instrument which allows the altitudes of objects in the night sky to be measured. Put together, these two components can be used the time of day, by determining the altitude of a star, and also at what time of day the sky’s rotation brings it to that height above the horizon.

Historically, the astrolabe was the most sophisticated astronomical instrument in widespread use in the Middle Ages. In fact, it held this position for nearly two thousand years, from the time of Hipparchus (c. 190–120 BCE) until the turn of the seventeenth century, around the time that the telescope was invented in 1609.

Yet today this complex instrument is rarely seen outside of glass cases in museums, and those interested in learning about it may have some difficulty finding a specimen to play with. Ornately carved brass reproductions are available from some telescope dealers, but with substantial price tags attached. These price tags are historically authentic: medieval astrolabes were often made from high-cost materials and intricately decorated, becoming expensive items of beauty as well as practical observing instruments. But for the amateur astronomer who is looking for a toy with which to muse over past observing practice, a simpler alternative may be preferable.

On this webpage, you can download a cardboard cut-and-glue kit to make your own model astrolabe, so that you can rediscover medieval observing practice for yourself.

What you need

• A printer (to print your astrolabe kit)
• Three sheets of thin card or paper
• A sheet of transparent plastic, e.g. acetate, which is safe to put through a printer
• Scissors
• Glue
• A split-pin fastener
• A short piece of ribbon or string

Instructions

Step 1 – Download our astrolabe kit (a PDF file). The exact layout of a astrolabe depends where on Earth it’s designed to be used from, since different stars are visible in the night sky from different places. We can supply a custom kit designed for use where you live. For your present location of Guyana, we recommend an astrolabe designed for latitude 10°N, which you can download here .

Step 2 – Print figures 1, 2 and 3 from the PDF file onto separate sheets of paper, or more preferably onto thin card. Print figure 4 onto a sheet of transparent plastic, such as acetate sheets sold for use with overhead projectors.

Step 3 – Cut out figures 1 and 2, which show the front and back sides of the astrolabe, and glue them back to back. You may wish to sandwich a piece of cardboard between them to make your astrolabe more rigid.

Step 4 – Place figure 4 (the rete), printed on the transparent plastic, over the front of the astrolabe.