ObjID31-1
‹ Ancient Sundials
Dialface ID 31
Page 1 of 3
Abstract
The sundial consists of two fragments. The right half was already known to Gibbs in 1976, the left half reappeared in 2005. Once covered with stucco, the left half has almost none of it left and is badly damaged, whereas on the right one some time indicating lines are still visible, as well as some traces of red colour on the base. On top, a construction line has been engraved. First fragment, Gibbs: Preserved portions of the gnomon hole indicate a depth of 28 mm. Second fragment, Severino: Questo frammento è stato ritrovato da Peppino Cesarano, assistito da Ciro Sicignano, il 17 marzo del 2005, in seguito alla mia visita a Pompei. I due funzionari della Soprintendenza, soggiogati dal fascino delle meridiane, hanno prestato attenzione ai nuovi ritrovamenti degli scavi attualmente aperti ed hanno trovato questo frammento di meridiana, probabilmente conica, in pietra calcare. Lo hanno inventariato e spostato nel deposito di Casa Bacco. Alt. 14,5 cm; base 11,5 cm; lunghezza 39 cm.
Measurements
Measurement record: pipeline ObjID 31, matched to this dialface by inventory number.
| Quality grade | B (completeness 79 %) |
|---|---|
| Dial surface | sphere (decisive) · fit residual mm: cone 1.84, cylinder 1.84, sphere 0.74 |
| Latitude φ | 45.45 ± 4.33° (consensus of witnesses) |
| Klima | Mid-Pontus (VI), Massalia, Borysthenes (VII) |
| Engraved lines | 7 hour lines, 2 day lines |
| Cone half-angle α | not shown: surface fit decisively sphere: cone-specific quantities do not apply |
| Measured | 2026-06-12 20:41 |
What the dial shows at this latitude
| Winter solstice | Equinox | Summer solstice | |
|---|---|---|---|
| Noon altitude of the Sun | 20.8° | 44.6° | 68.3° |
| Noon shadow (gnomon heights) | 2.63 | 1.02 | 0.40 |
| Length of the day | 8.5 h | 12.0 h | 15.5 h |
| Length of a seasonal hour | 42 min | 60 min | 78 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.
References
- – Gibbs, Sharon L., Greek and Roman Sundials, New Haven and London, 1976, p. 147, p. 165, plate 7.
- – Severino, Nicola, De Monumentis Gnomonicis apud graecos et romanos. Le meridiane greco-romane. La storia, il catalogo, gli articoli, Roccasecca, 2003, p. 25, p. 30.
3D Models
