ObjID188-1
‹ Ancient Sundials
Dialface ID 187
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Abstract
The gnomon hole has a semicircular vertical section 50 mm wide and 51 mm deep. Eleven hour lines extend from winter to summer solstice. The three day curves have been engraved always equidistant from each other and from the lower edge of the conical surface. Dots are visible at the junctions of hour lines and winter solstice.
Measurements
Measurement record: pipeline ObjID 188, matched to this dialface by inventory number.
| Quality grade | A (completeness 95 %) |
|---|---|
| Dial surface | cone (decisive) · fit residual mm: cone 2.27, cylinder 5.54, sphere 10.08 |
| Latitude φ | 22.23 ± 0.56° (consensus of witnesses) |
| Klima | nearest Syene (2.9 sigma) |
| Engraved lines | 10 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 20:33 |
What the dial shows at this latitude
| Winter solstice | Equinox | Summer solstice | |
|---|---|---|---|
| Noon altitude of the Sun | 44.1° | 67.8° | 88.5° |
| Noon shadow (gnomon heights) | 1.03 | 0.41 | 0.03 |
| Length of the day | 10.6 h | 12.0 h | 13.4 h |
| Length of a seasonal hour | 53 min | 60 min | 67 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
- – British Museum, Department of Egytian, Antiquities, Assyrian, A Guide to the Egyptian Collections in the British Museum, London, 1909, p. 72 (photograph) and p. 273.
- – Scott Gatty, Margaret, The Book of Sun-dials, London, 1900, p. 32 (drawing) and 42 f.
- – Gibbs, Sharon L., Greek and Roman Sundials, New Haven and London, 1976, p. 304, p. 305, plate 48.
- – Hannah, Robert, Time in Antiquity, London, 2009, 127-131.
- – Löschner, Hans, Über Sonnenuhren: Beiträge zu ihrer Geschichte und Konstruktion nebst Aufstellung einer Fehlertheorie, Graz, 1906, p. 31.
- – Winter, Eva, Zeitzeichen. Zur Entwicklung und Verwendung antiker Zeitmesser, Berlin and Boston, 2013, p. 257f.
3D Models
