An astrolabe is a two dimensional representation of the cosmos as originally presented by Ptolemy in his Tetrabiblios. Such instruments were used throughout the Middle Ages and the Renaissance by scholars, astronomers and ship pilots to track the position of the stars. An astrolabe is a model of the universe that can be held in the hand. To use an astrolabe, you adjust the moveable components to a specific date and time. Once set, the entire sky (visible and invisible), is represented on the instrument's surface.
Working Materials
Paper: Pergamenata (vegetable-based vellum paper).
Calligraphic Ink: Oak gall ink made with period recipes and materials including oak galls, iron salts, logwood dyes and acacia gum (Gum Arabic).
Pen: Handcrafted oak-handle, metal nib.
Wood: Pressed wood, cut with dremel and hand-sanded.
My Project Astrolabe

Mathematical design
The mater, rear, and rete of the astrolabe are similar in design from place to place, and were simply implemented with slight modifications for Seattle's latitude. The tymphan, or plate for each latitude line, had to be completely constructed with mathematics to make it accurate to Seattle's latitude (47 2/3 degrees north of the equator).

Construction design: The astrolabe was constructed according to the descriptions given in Geoffrey Chaucer's Treatise on the Astrolabe, and also checked against several medieval astrolabes of the 15th and 16th centuries to confirm visual style and apparent use. The final rete is slightly different from that described in Chaucer's Treatise, in order to better distinguish stars utilized in the fifteenth century (rather than the fourteenth). This will be essential in future uses of this astrolabe for A&S projects in astronomy.

Period Astrolabe

Science in the Renaissance was focused around the major sciences of astrology, geometry, medicine, magic and alchemy. Astronomy was taught and respected for centuries during the middle ages, where the study of the sky was considered as necessary as any other science, but 'civilized' or functional astronomy did not truly come into its own until the renaissance. The study of astronomy requires several unique tools, among which are the telescope, the sexton, the planar tables, and perhaps most importantly, the astrolabe.

The word astrolabe is a compound term from the Greek, meaning 'to follow the stars,' and that is exactly what the tool does. A planispheric astrolabe is an ancient astronomical device for solving problems of time, special relations, and the position of the Sun and stars in the sky, on which the celestial sphere is projected onto the plane of the equator.


An astrolabe shows the sphere of the heavens; the earth is at the center, showing the movement of the celestial sphere around the pole and allowing the relative position of stars to be determined at any given. It is, as it were, a model of the universe that can be held in the hand.

Astrolabes show how the sky looks at a specific place at a given time. To use an astrolabe, you adjust the moveable components to a specific date and time. Once set, the entire sky, both visible and invisible, is represented on the face of the instrument. Classical astrolabes were usually made of brass and were commonly about six or eight inches (15 to 20 cm) in diameter, although much larger and smaller ones were made. A typical student's astrolabe was made of paper and wood, but more decorative and sturdier astrolabes were often constructed of brass or other metals.

The astrolabe is an integral tool for practicing the arts of the astrologer and astronomer, and provides a tangible representation of the celestial sphere. Typical uses of the astrolabe include finding the time during the day or night, finding the time of as sunrise or sunset and as a handy reference of celestial positions. Essentially, the astrolabe is an analog computer for finding the position of bodies in the heavens relative to the local horizon. Given the time and date, a skilled astronomer can use an astrolabe to calculate most of the astrological positions for casting a horoscope, lacking only the positions of the planets, which would be provided by a set of tables for the appropriate year.

The parts of an astrolabe
Parts and Pieces
The astrolabe when the center pinning is removed.
Pieces before construction.