The Way to the Stars: Build Your Own Astrolabe

Build Your Astrolabe: The Constellations

Use the images below to locate and label some of the most recognisable stars and constellations on the rete of your astrolabe. You will need a permanent marker to write on the transparency. The constellations below are labelled with CAPITAL LETTERS, the stars are named in lower case.

Click on the links in the text to see artistic represantaions of the constellations from some of the Library's early printed books (or visit the Library Picture Gallery to see them all at once) and photographs of the night sky. Images of the night sky showing the constellations are mirror images of the shapes seen on the rete. This is because the rete shows the stars as if the viewer were outside the imagined sphere of the heavens. Views of the night sky are, however, obviously from within the sphere.

If you would like to label more features on your rete, you can use an online source such as the International Astronomical Union's list of official constellations.

Orion, The Hunter

This constellation is named after the hunter Orion in Greek Mythology. It is easily spotted in the winter sky with its central belt of three stars in a row.

The star Betelgeuse is a red giant star, and its orange/red coloration is clearly visible with the naked eye. Rigel is the sixth brightest star in the sky. It is a blue giant, 17 times more massive than our sun and about 40,000 times as luminous.

Diagram of the constellation Orion

Cassiopeia, The Queen

The constellation of Cassiopeia has a distinctive shape similar to the letter 'W'. It shows the vain Queen Cassiopeia sitting on her throne. Caph is the second brightest star in the constellation. As with many named stars, its name is derived from an Arabic root.

Diagram of the constellation Cassiopeia

Cygnus, The Swan

Cygnus has the shape of a swan in flight as seen from above (or below).

The three bright stars Vega, Deneb and Altair are together known as The Summer Triangle, as they are clearly visible overhead on clear summer nights.

Diagram of the constellation Cygnus

Ursa Major, The Great Bear

The constellation Ursa Major can be seen as a bear walking on all fours with its snout stuck out in front. Part of the constellation (including the bear's tail) makes up probably the most recognisable shape in the night sky, The Plough, or the Big Dipper. Its distinctive shape is reminiscent of a saucepan, but is not classified as a constellation in its own right.

The bright star Arcturus is part of the constellation of Boötes. Its name comes from the ancient Greek ???t????? (Arktourus), meaning "guardian of the bear". This name refers to its proximity to Ursa Major and Ursa Minor (the constellations of the Great and Little Bears).

Diagram of the constellation Ursa Major

Two Bright Stars in the Winter Sky

Siruis is the brightest star in the sky. It forms part of the constellation Canis Major, the Great Dog, and was formerly often depicted as the nose of the dog, though today it's normally seen as part of the dog's neck. It is popularly known as the Dog Star.

Procyon is the seventh brightest star in the sky, and the brightest star in the small constellation of Canis Minor, The Small Dog. Although this is not visible with the naked eye, it is actually a binary star system: two stars orbiting each other at close distance.

Both Sirius and Procyon are so bright because partly they are some of the closest stars to earth. They lie approximately 8.6 and 11.4 light-years away respectively. The closest star to earth is Proxima Centauri, which lies about 4.2 light-years away. A light-year is the distance travelled by light in a vacuum in one year, and is equal to 9,460,730,472,580.8 km.

Diagram showing the bright stars Procyon and Sirius

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