Accession No
0476
Brief Description
dynameter, by Banks, English, 1871
Origin
England; London
Maker
Banks
Class
astronomy; optical
Earliest Date
1871
Latest Date
1871
Inscription Date
1871
Material
metal (brass, silver); glass; wood; paper; cloth (velvet)
Dimensions
length 52mm; diameter 26mm case length 61mm; breadth 69mm; thickness 32mm
Special Collection
Robert Whipple collection
Provenance
Purchased by Robert Stewart Whipple from T. H. Court in 1929.
Inscription
‘BANKS
LONDON’
Description Notes
Dynameter in brass tube with push-fit cover. Semi-lenses moved by micrometer screw. Silvered drumhead divided [0] - 10, numbered by 1, graduated to 0.2.
Wooden box covered with red paper and lined with green velvet; brass hinges and push-button fastener; paper in base carries MS notes on use of dynameter; lid marked ‘Dynameter’ in ink MS; dated ‘Nov 1871’ inside lid by hinge.
Condition good; complete
References
Events
Description
Micrometer
Micrometers were used mainly by astronomers and microscopists to measure objects. They were first devised in about 1609 and used the exact number of turns of a screw to measure small distances. Micrometers were inserted into the path of a telescopes and microscopes, and were also used to accurately measure quadrant scales.
Early examples of the micrometers used in telescopes were calibrated geometrically using a piece of card at a distance of about 200m with lines of known separation on it. However, this introduced inaccuracies of a few seconds of arc due to the closeness of the card compared with the distance of real observations. It was not until 1672 that this problem was overcome and accurate calibration was possible.
18/10/2002
Created by: Saffron Clackson on 18/10/2002
FM:39684
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