Nocturnal (back)

A nocturnal shows the local time at night, by measuring the rotation of the constellations of the Great Bear and the Little Bear around the Pole Star. This boxwood example was made in England around 1740. The photograph shows the back of the instrument.

The back of the nocturnal has two concentric scales giving the corrections to the altitude of the Pole Star for use in finding latitude. These are used together with the long index arm.

Wood was the usual material for English nocturnals. On the Continent, they were often made of brass.

Record details

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Online ID:	000-190-001-073-C
Image Rights Holder:	National Museums Scotland
Project:	0098: National Museums Scotland Project description \| View all records in project
Ref:	National Museums Scotland T.1984.60
Date:	Around 1740 c. 1740
Material:	Boxwood
Dimensions:
What:	Nocturnal
Subject:
Who:
Where:	England
Event:
Description:	Boxwood nocturnal of English manufacture, c. 1740
References:	For a description of how the nocturnal works, see Bennett, J.A., The Divided Circle: A history of instruments for astronomy, navigation and surveying. Oxford: 1987, pp 77-9
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