Eyepiece double-image spherical crystal micrometer

Made:
1830 in London
maker:
George Dollond

Eyepiece double-image spherical crystal micrometer using a made by George Dollond in 1830 for the Smyth telescope (1929-949 Pt1 ).

Captain W.H.Smyth used this Crystal micrometer to measure double stars for his famous book, 'A Cycle of Celestial Object' first published in 1844. The novel design of the instrument caused ambiguity in his readings which after his death resulted in accusation of inaccuracy and plagiarism. Charges that were shown subsequently to be unfounded (see 'An Astronomical Scrapbook' by Joseph Ashbrook, Cambridge 1984).

Details

Category:
Astronomy
Object Number:
1929-949 Pt5
Materials:
brass and glass
Measurements:
Estimate overall: 100 mm 60 mm,
type:
instrument component
taxonomy:
  • furnishing and equipment
  • measuring device - instrument
  • micrometer - angle
  • double image micrometer
  • component - object
credit:
Royal Observatory, Greenwich