Stock Number: 7044


For sale, an early diminutive case-mounted Gregorian telescope from the 18th century The brass telescope assembly mounts to lid, with a main tube fitted with two speculum metal mirrors, and erecting optics.


7-1/4 main tube


Second quarter 18th century

Country of manufacture

UK and Ireland

Categories: Telescopes - Reflecting, Telescopes


DIMINUTIVE EARLY CASE-MOUNTED GREGORIAN TELESCOPE, probably English, c. second quarter 18th century. The 8-5/8″ x 3-1/2″ x 2-3/4″ (22 x 9 x 7 cm) mahogany or rosewood case has oak bottom and beveled slide-off lid, plus inset brass mounting plate and beautiful brass escutcheon. The brass telescope assembly mounts to the lid, by tapered steel screw and turned brass pillar to altazimuth mount. The main tube is 7-1/4″ long and 1-5/8″ in diameter, fitted with spring-loaded speculum metal primary mirror, speculum secondary mirror on adjustable mount driven by external focusing rod, erecting eyepiece assembly with two lens elements and two apertures, screw-on red solar filter, and turned end cap. The system gives remarkably fine images, even in daylight when the Gregorian design suffers from off-axis light. Condition is fine noting some darkening to the brass, a couple of replaced mounting screws, and old repair to the lock.

Various details point to an early date — the use of oak as a secondary wood, the escutcheon form, telescope design details, the diminutive size, the case-top mounting, etc. We have seen an even smaller case-mounted Gregorian by Edward Scarlett, and note James Short’s frequent use of this design.

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David and Yola Coffeen both have enjoyed academic careers, as planetary astronomer and as linguist/educator. But since 1982 (yes, 1982!) they have been full-time dealers in early scientific and medical instruments, under the name Tesseract. Selling primarily by catalogue (over 100 issued so far) they also have a web presence at, and can be contacted at [email protected].

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