Display Status:

This object is not on display at the National Air and Space Museum. It is either on loan or in storage.

Collection Item Summary:

This is a filar micrometer, likely made by Brashear of Pittsburgh, and used visually on the 24 inch refractor of the Sproul Observatory, Swarthmore College since its opening in 1913. It contains tiny electrical lamps, and some later modifications. Designed by Klages of Brashear, it connects to telescope by bayonet mount. Filar micrometers were precursors for double star positional astronomy and astrometry prior to the photographic era.

Swarthmore College donated this set of objects to the Museum in 2017.

Collection Item Long Description:

Inventory Number


Credit Line

Donated by Swarthmore College

Country of Origin

United States of America


Mixed metals, brass, some wooden parts, glass optics


3-D: 34.3 × 30.5 × 21.6cm, 14.4kg (1 ft. 1 1/2 in. × 1 ft. × 8 1/2 in., 31.7lb.)

Data Source

National Air and Space Museum

Restrictions & Rights

Do not reproduce without permission from the Smithsonian Institution, National Air and Space Museum


EQUIPMENT-Scientific Devices