Ancient Sundials

Dialface ID 337

ObjID295-1

Holder:: Soprintendenza Speciale per i Beni Archeologici di Napoli e Pompei, Pompei, Italy
Site:: Pompei, Italy
Material:: Tufa, With Stucco
Dating:: unknown
Type:: Sphere, Spherical
Inventory Number:: 20495
Site Geolocation:: Lat.: 40.7503, Long.: 14.4871

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Abstract

Un bellissimo frammento che conserva le ore dalle 7 alle 11. L'accuratezza del tracciato delle linee testimonia che un tempo era una meridiana davvero ben fatta. Conserva perfettamente la colorazione rossa per ciascuna linea e le due porzioni di solstizi.

Measurements

Measurement record: pipeline ObjID 295, matched to this dialface by inventory number.

Quality grade	C (completeness 86 %)
Dial surface	sphere (decisive) · fit residual mm: cone 1.67, cylinder 4.46, sphere 0.46
Latitude φ	41.00 ± 0.31° (single witness: path-III-front-back)
Engraved lines	5 hour lines, 3 day lines
Cone half-angle α	not shown: surface fit decisively sphere: cone-specific quantities do not apply
Measured	2026-06-12 20:40

What the dial shows at this latitude

	Winter solstice	Equinox	Summer solstice
Noon altitude of the Sun	25.3°	49.0°	72.7°
Noon shadow (gnomon heights)	2.12	0.87	0.31
Length of the day	9.0 h	12.0 h	15.0 h
Length of a seasonal hour	45 min	60 min	75 min

Computed for the measured latitude with the obliquity of the JPL ephemeris at 101 BC (year -100). The latitude is the one the dial was made for, not a find-spot coordinate.

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References

– Severino, Nicola, De Monumentis Gnomonicis apud graecos et romanos. Le meridiane greco-romane. La storia, il catalogo, gli articoli, Roccasecca, 2003, p. 19.