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Two Prismatic Lenses

Unidentified · Astronomy

These are two cylindrical brass optical instruments, each with an angled prism fitted inside the tube and a toothed gear around the circumference of the base. The prisms appear to fill most of the cylinder and are parallelogram shaped, with diamond-shaped, angled end faces. Each lens has threads on the prism end of the interior of the tube. These interiors have been painted black up to where the threads begin.

2018.ast.86.1 is the longer lens. On this lens, the gear is located about 2cm from the end of the tube.

2018.ast.86.2 is the shorter lens. On this the gear is at the end of the tube. Just above this there is a scale graduated in 360 degrees, marked in 30s.

Accession Number: 2018.ast.86.1-2

Alternative Name:

Primary Materials: Metal: Copper Alloy, Glass, Wood: Cork?

Markings: None.

Dimensions (cm):

2018.ast.86.1: Height = 12.3, Diameter = 7.6; 2018.ast.86.1: Height = 10, Diameter = 7.5



Very Good: Both lenses show signs of use but are intact and in good condition. There is wear in the form of parallel scratches around the circumference of the barrels of each tube and wear on the threads of the screws inside the tubes. The scale on 2018.ast.86.2 is somewhat corroded.

Associated Instruments:


Date of Manufacture: Early 20th Century


This object was likely moved from the David Dunlap Observatory in Richmond Hill in 2008, upon the sale of the observatory. It was stored at the Department of Astronomy and Astrophysics until 2017, when it was moved to a new storage location in McLennan Physical Laboratories.

Additional Information and References:

Historical Notes: