Small Reflecting Telescope

Signature

Date

Late 1700s

Dimensions

English

Metric

Main Tube Length

5.2in

131mm

Main Tube Diameter

1.2in

31mm

Total Length

7.1in

180mm

Primary Mirror Diameter

1.0in

25mm

Description

This telescope has a very small brass cylindrical barrel. The primary mirror is a concave paraboloid, with a central hole, and is kept in place at the rear of the barrel with a screw-in backing plate. The small secondary mirror is a concave ellipsoid. It is attached by a slender arm to a screw-driven carrier which slides along the front interior part of the barrel. This configuration of primary and secondary mirrors is called Gregorian. Both mirrors are speculum. The focusing thumbscrew, at the eyepiece end of the barrel, attaches to the secondary mirror carrier through a slot near the eyepiece end of the barrel. The eyepiece tube screws into a hole in the center of the backing plate, which holds the primary mirror in place. The two-lens eyepiece is the Huygens type. The telescope is not signed by the maker. This telescope is certainly among the smallest ever produced.

College of Optical Sciences
The University of Arizona, 1630 East University Boulevard, Tucson, Arizona U.S.A. 85721-0094