ObjID498-1
‹ Ancient Sundials
Dialface ID 540
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Abstract
Three day curves are divided unevenly by eleven hour lines. A simple engraved design decorates the oblique front surface.
Measurements
Measurement record: pipeline ObjID 498, matched to this dialface by inventory number.
This object is registered in the measurement database, but its own record holds no measured values; see the variants below.
Variant NotSelectedPoints
| Quality grade | B (completeness 86 %) |
|---|---|
| Dial surface | cone (decisive) · fit residual mm: cone 0.89, cylinder 4.19, sphere 5.79 |
| Latitude φ | 39.78 ± 5.10° (consensus of witnesses) |
| Klima | Hellespont (V), Athens, Rome |
| Engraved lines | 10 hour lines, 3 day lines |
| Cone half-angle α | 32.1 ± 0.14° (cone residual on all points 0.91 mm) |
| Measured | 2026-06-12 20:49 |
What the dial shows at this latitude
| Winter solstice | Equinox | Summer solstice | |
|---|---|---|---|
| Noon altitude of the Sun | 26.5° | 50.2° | 73.9° |
| Noon shadow (gnomon heights) | 2.00 | 0.83 | 0.29 |
| Length of the day | 9.1 h | 12.0 h | 14.9 h |
| Length of a seasonal hour | 46 min | 60 min | 74 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
- – Avellino, F. M., Descrizione di una casa Pompejana, Naples, 1837, plate 10, 12.
- – Gibbs, Sharon L., Greek and Roman Sundials, New Haven and London, 1976, p. 293.
- – Severino, Nicola, De Monumentis Gnomonicis apud graecos et romanos. Le meridiane greco-romane. La storia, il catalogo, gli articoli, Roccasecca, 2003, p. 21.
3D Models
