sundial
Object NameGrand Universal Equinoctial Dial with Precision Oculus
Maker
Pierre Mégnié
(French, fl. 1751-1807)
Made FromBrass, Glass
Dateabout 1790
Place MadeSpain, Madrid
TechniqueRolled, ground, polished
SizeClosed H: 4.6 cm, W: 21.5 cm, D: 21 cm; Open H: 14. 5
Accession Number2018.8.2
Curatorial Area(s)
Not On View
Physical DescriptionGrand Universal Equinoctial Dial with Precision Oculus. Rolled brass, ground and polished glass lens. Brass horizontal sundial with main plate measuring 19.5 x 21 cm, set with three leveling screws, crossed spirit levels, and freely rotatable central circular dial plate. The latter is set with a large hinged chapter ring engraved with scales in both Roman and Arabic numerals, divided every five minutes from 4 am to 8 pm. This equinoctial ring is inclined against a hinged latitude arc divided every half-degree 0° to 70°. The hour ring has a crossbar carrying the gnomon, which swivels flat for stowage, upwards for summer when the sun is above the celestial equator, and downwards for winter. Rather than the typical needle gnomon, there is an oculus with a tiny lens, swiveling and adjustable vertically for solar declination from 0° to 23-1/2°, with readout by a grid of transversals to five arcminutes.Provenance
Source
Tesseract
- 2018-01-02
701-899
