ObjID18-1
‹ Ancient Sundials
Dialface ID 18
Page 1 of 2
Abstract
The planes of the corpus are undecorated.
Measurements
Measurement record: pipeline ObjID 18, matched to this dialface by inventory number.
| Quality grade | B (completeness 100 %) |
|---|---|
| Dial surface | cone (preferred, not decisive) · fit residual mm: cone 2.72, cylinder 3.10, sphere 3.02 |
| Latitude φ | 41.45 ± 0.37° (consensus of witnesses) |
| Klima | Rome, Hellespont (V) |
| Engraved lines | 11 hour lines, 3 day lines |
| Cone half-angle α | not shown: the derived cone does not agree with the measured points (residual 8.9 mm; verified cones give under 1 mm); under review |
| Measured | 2026-06-12 20:31 |
What the dial shows at this latitude
| Winter solstice | Equinox | Summer solstice | |
|---|---|---|---|
| Noon altitude of the Sun | 24.8° | 48.6° | 72.3° |
| Noon shadow (gnomon heights) | 2.16 | 0.88 | 0.32 |
| 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.
References
- – Scott Gatty, Margaret, The Book of Sun-dials, London, 1900, p. 31.
- – Gibbs, Sharon L., Greek and Roman Sundials, New Haven and London, 1976, p. 133.
- – Smith, Arthur Hamilton, A catalogue of sculpture in the Department of Greek and Roman Antiquities, British Museum, London, 1904, vol. 3, p. 414, no. 2547.
- – Ward, Francis Alan Burnett, Time Measurement. Handbook of the Collection Illustrating Time Measurement, London, 1948, p. 17, plate 2.
- – Ward, Francis Alan Burnett, Descriptive Catalogue of the collection illustrating time measurement, London, 1950, p. 11.
3D Models
