An astrolabe is an astronomical instrument; it was used for surveying the positions of the stars and planets, and calculating sidereal time. The device is period – Chaucer wrote a “Treatise on the Astrolabe” c.1391, in which he translated earlier Moslem texts – but no examples of it have been found in period armory. In Society heraldry, the astronomer’s astrolabe is granted no difference from a roundel.
A simplified form of astrolabe, the “mariner’s astrolabe”, was used for navigation; it’s distinguished by large holes in the plate, so the wind wouldn’t interfere with surveying. While it too was a period artifact, dating from Portugal c.1480, no armorial examples have been found.
David MacColin bears: Per chevron throughout sable and argent, two open penannular brooches palewise, pins to base, and an astrolabe counterchanged.
Duncan Ramsay bears: Quarterly gules and vert, an astrolabe within an orle wavy Or.
Vincent McThomas bears: Argent, a mariner’s astrolabe azure and a ford proper.