Equinoctial Pocket Sundial

Astronomy

Accession Number: 2019.ast.259

Description:

This is a small sundial. It consists of an octagonal base engraved with ornate carving. In the centre of this there is a circular opening covered by glass window which covers a compass. The compass has a central freely rotating indicator needle and a compass rose engraved on the base. Lines emerge from this and are labelled in pairs of letters, one letter appearing on each side of each line: “O|C” “S|E”
“O|R” “M|E”.

Affixed on a hinge to one side of the octagonal base there is a circular ring. This can be raised and lowered from lying flat on the base to standing perpendicularly to it. The angle of the ring can be measured on a arc-shaped scale, graduated in degrees; this is also hinged and affixed to another side of the base and can also be laid flat. Across the centre of this ring there is a thin rod and affixed perpendicularly to the centre of this rod a small needle-shaped rod.

Engraved around the rim of the rod are Roman numerals. On the underside of the compass there is a metal label with writing on it.

Alternative Name:

Equinoctial Compass, Equinoctial Sundial, Augsburg Sundial

Primary Materials: Metal: Copper Alloy, Metal: Iron Alloy

Markings:

On the base of the instrument: “ElevaPoli
Lisbon39Rom
42Venedig45Wien
AugspMunchen
SalzbStrasb
48NurnbHeidl
49LTM”

Function:

This instrument was designed to be a portable tool that would permit the user to tell the time by shadows cast by the sun. The compass would assist with correctly orienting the instrument. The cities listed on the base of the instrument indicate latitudes of major European cities, which enabled accurate usage. This is likely a mass-produced item.

Condition:

Excellent: The surfaces of the instrument are in very good condition, with little sign of corrosion. The gnomon, ring and arced scale are oxidized. The hinges that attach these pieces are in good condition and move smoothly. There are a few very small spots of corrosion on the internal surface of the base of the compass.

Manufacturer:

Ludovicus Theodatus Müller (L.T.M.), Ausgberg

Date of Manufacture: c. 1710-1790

Provenance:

This instrument was acquired as an antique by Reynold K. Young, former Director of the David Dunlap Observatory (1935-1946), likely as a display object. Since, it has been either on display at the department or in storage at the David Dunlap Observatory in Richmond Hill, or at the Department of Astronomy and Astrophysics building on the St. George Campus at the University of Toronto.

Additional Information and References:

Information about instruments of this kind can be found at compassmuseum.com. [17/10/19]

The maker, who signed the instrument “L.T.M.”, was identified with the use of this chart at adlerplanetarium.org. [17/10/19]