Universal Equinoctial Ring-Dial

Date1752-1800

Object number00047666

NameUniversal ring dial

MediumBrass

DimensionsOverall: 140 x 110 x 15 mm

ClassificationsTools and equipment

Credit LineANMM Collection Gift from Sydney Training Depot

Terms

DescriptionThis Universal Equinoctial Ring Dial is a brass sundial used for navigation. It was popular as a simple and functional time-piece during daylight hours. Ring dials were in use from the 1600s to the mid-nineteenth century. It remained popular as a dependable back up, even after accurate timekeepers were developed. HistoryThis universal ring dial, or more correctly Universal Equinoctial Ring Dial, is a portable sundial used for navigation. It was used for determining time during daylight hours and in use from the 1600s to mid-nineteenth century. The dial is termed 'universal' as it can be used in both hemispheres. The universal equinoctial ring dial was developed from the astronomer's ring of the 16th century. Described as 'a simplified armillary sphere consisting of three or four rings, with pinhole sights', the astronomer's ring was used for measuring altitudes of stars and terrestrial objects. A two-ring dial soon developed from this type of instrument. Early versions carried only a date scale on the bridge and were normally for use in northern latitudes alone. Towards the end of the 17th century, zodiac and solar declination scales were added to the bridge and a further degree scale was supplied to allow the use of the instrument in southern latitudes. At the same time, an altitude quadrant appeared on the back, which was used for measuring heights, in conjunction with a stylus set in a hole in the back of the instrument. These improvements made the universal equinoctial ring dial suitable for use at sea. Compared to surviving ring dials, this example is functional but plain and has no maker's marks. Other ring dials in the large collection held by the National Maritime Museum, London show fine detailing and embellishment. British manufactured items were in general less adorned than continental ones. The construction, shape and form of the ring dial did not change perceptibly from the 1600s. This ring dial is consistent with examples from the 1700s to the early 1800s. Ring Dials were commonly issued with instructions by the manufacturer. A photocopy of a hand-written copy of instructions titled 'The Description & Use of the Equinoctial, commonly called the Ring-Dial' is associated with this object. This ring dial was owned by a Norfolk Island resident and from the 1970s on display at the Tingara Old Boys Association museum and then at the Sydney Training Depot museum at Snapper Island from 1984 to 2008. According to museum records, the ring dial was purportedly associated with Captain Bligh; however there is no evidence to confirm this. SignificanceThis Universal Equinoctial Ring Dial is a good example of what was an important navigational aid that remained in use from the 1600s to the mid 1800s in a largely unchanged form.

This ring dial has purported associations with William Bligh.