Geared Astrolabe by Muḥammad ibn Abī Bakr

Technical characteristics

Date

1221/2 (A.H. 618)

Type

Geared astrolabe

Maker

Muḥammad ibn Abī Bakr

Material

Brass

Provenance

Lewis Evans (1924), previously Raoul Heilbronner (1913)

Mechanism type

Geared gear train

Place recorded

Iṣfahān

Maker / attribution

Muḥammad ibn Abī Bakr

Place of manufacture

Iṣfahān

Design

Rete and Throne

It is populated by three distinct zoomorphic star pointers: a bird identified as a falcon representing Vega, a diving bird pointing to al-Tayir, and a horse pointing to Mankib. The ecliptic is decorated with a quatrefoil at its center. The throne is of a pierced Indo-Persian style, featuring an integrated base and a simple, square-section ring. It is attached to an omega-shaped shackle, a configuration that serves as the instrument's primary suspension point. The rete is secured by a pin and wedge, which also functions as the drive axle for the internal gear mechanism, though this component is considered a later replacement.

Visible features

• Pierced Indo-Persian style throne • Three zoomorphic pointers on the rete including a falcon and a horse • Detailed Arabic inscriptions surrounding the back perimeter and central windows • Internal gear train visible when back plate is opened

Construction and Mechanism

The instrument is fabricated from brass and features a one-piece mater and limb construction. The core functionality relies on a mechanical gear train consisting of five cogs located between the back plate and the interior of the mater. This train is driven by an axle connected to the rotating rete on the front. This mechanical arrangement synchronizes the front rete rotation with three specialized calendrical diagrams on the back. The back plate displays lunar phases in an upper circular window, the moon's age in a rectangular window, and the relative positions of the sun and moon within the zodiac in a lower moving volvelle window. The designer employed a simplified gear configuration that required only one cog to feature an odd number of teeth.

Signatures and Inscriptions

The instrument is marked with extensive Arabic script, which provides both technical instructions and the maker's identification. The signature of Muḥammad ibn Abī Bakr ibn Muḥammad al-Rāshidī al-Ibarī al-Iṣfahānī is inscribed across the center of the back. The back also contains a philosophical passage inscribed around the entire rim, explaining the movement of celestial bodies and attributing the instrument's design to verification and demonstrative proof. Additional scale labels around the lunar and age-of-moon windows provide user guidance for interpreting the calendrical functions. An early owner, Ḥasan Shāh, added a rough inscription to one of the calendar wheels, providing evidence of the object's history before its entry into the Evans collection.

Identification

Inventory number

48213

Source note

Facts transcribed from the linked source listing or collection record. Attribution and specifications are source-reported and have not been independently authenticated.

Catalogue references

No catalogue numbers recorded. Numbers are only published once transcribed from a verified edition of a standard catalogue — they are never inferred.