Ancient Greek origins; developed from the 8th century CE
◐Approximate date
Hellenistic world, then Baghdad, Al-Andalus and beyond
Associated with
Hellenistic astronomers
Developed the mathematics of projecting the sky onto a plane
Islamic astronomers and instrument makers
Refined the instrument; al-Fazari is reputed as an early maker
Plate 038
Ancient Greek origins
Hellenistic world, then Baghdad, Al-Andalus and beyond
No photograph is shown for this exhibition. The museum displays an image only where it can show the object honestly.
About this date
The planispheric astrolabe has Hellenistic roots. Islamic astronomers developed it extensively from the 8th century. Specific first makers are reputed but not securely documented.
About credit
The astrolabe is a product of several traditions. Different features were added in different places.
Chapter II
The world before
Life before the Astrolabe
Astronomical calculations were done with tables and long computations.
II
The human achievement
How it came about
The astrolabe projects the celestial sphere onto a flat plate. A rotating rete, a pierced star map, sits on top of plates engraved for specific latitudes. Sighting along a rule measures a star’s altitude, from which time or latitude can be read.
III
Understanding the invention
How it works
The Astrolabe, explained in two steps.
01
Step 01 of 02
A sky on a plate
The rete’s pointers mark bright stars, and turning it simulates the rotation of the sky.
A sky on a plate
Measuring altitude
IV
The transformation
What changed for humanity
Timekeeping and prayer
Muslim astronomers used it to find prayer times and the direction of Mecca.
Teaching
It was a standard tool for teaching astronomy in universities.
It combined many astronomical calculations in one hand-held tool and was used for timekeeping, surveying, astrology and finding prayer times and the direction of Mecca.
V
Before and after
Life before and after The Astrolabe
Before
Estimating from the stars.
After
Reading it off a dial.
On larger screens, drag the divider (or use the arrow keys) to give more room to the world before or after.
VI
Its legacy
What came after
MHI 038
The Astrolabe
Beyond the collection
The Sextant
Specialised instruments for navigation followed.
Beyond the collection
Modern navigation
Celestial navigation developed from such instruments.
VII
Human stories
The people and the moments
Chaucer’s treatise
Geoffrey Chaucer wrote a Treatise on the Astrolabe in the 1390s for his young son Lewis, one of the earliest technical manuals in English.
Where accounts differ, this museum follows the documented record and says so.
