Equinoctial Sundial by Peter Dollond
date: label: date made
content: late 1700s
name: label: maker
content: Dollond, Peter
notes: label: Description
content: This brass universal equinoctial ring dial consists of a meridian ring, hour ring, rotating crosspiece or bridge, and sliding suspension ring/handle. The base of the suspension ring is marked with a vernier for the meridian ring that reads to 3 minutes of accuracy. The meridian ring is calibrated on one side for northern and southern latitudes from 0 to 90 to 0 x 2 by single degree. The reverse contains an elongated nautical quadrant for solar altitude calibrated 90 to 0 by half-degree and from 0 to 90 by 10 degrees. The hour ring is calibrated from I to XII x 2 by I. The hour ring is also divided by minutes (20, 40, 60) underneath the hour marks and along the inside edge of the hour ring. The bridge contains a pinhole gnomon sliding over a calendar scale calibrated by month (in 3-letter abbreviations) and day. An engraved line on either side of the pinhole enables the user to line up the gnomon with the proper calendar day. The reverse of the bridge contains a declination scale from 20 to 0 to 20 by units of 0.5 and labeled with S.D. (south declination), AE (equinox?) and N.D. (north declination). The reverse of the bridge also contains a zodiacal sign scale divided into 30s. There is a fitted black or blue leather and wood case with green velvet lining for this instrument.
label: Description
content: There were numerous instrument makers named Dollond, but Peter Dollond is known to have sold sundials in the late 1700s.
label: Location
content: Currently not on view
place: label: place made
content: United Kingdom: England, London
topic: label: Subject
content: Mathematics
label: Subject
content: Timekeeping
setName: label: See more items in
content: Medicine and Science: Mathematics
label: See more items in
content: Science & Mathematics
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: MA.326980
label: catalog number
content: 326980
label: accession number
content: 272472
objectType: label: Object Name
content: sundial, equinoctial
physicalDescription: label: Measurements
content: overall: 3 cm x 20 cm x 28 cm; 1 3/16 in x 7 7/8 in x 11 1/32 in