Noon-mark dial for setting the time on watches c1760
The noon dial or noon mark is an ancient way for telling the time of midday. The sun is at its highest and is due south then.
By the eighteenth century, and continuing until the early twentieth century, noon dials and other types of sundial were used for setting clocks and watches. The method for working out clock time needed the Equation of Time, because clock time is the average of sundial time round the year.
The Noondial is a modern sundial by Alastair Hunter that embraces the noon dial concept, shows the Equation of Time, and provides a number of sundial readings. The reading point is the light spot at the centre of the shadow disc. It sweeps across the dial from left to right each day, and slowly travels down the dial and up again through the year.
In full, Alastair Hunter’s Noondial reads …
- sundial time with one hour, half-hour, and ten minute graduations
- 12 o’clock GMT (and 1 o’clock BST) on the figure-of-eight loop that corresponds to the Equation of Time and is called the Analemma
- calendar date at one month and five day intervals
- seasons of the year—winter and summer solstice, and spring and autumn equinox
- length of day in hours from sunrise to sunset
- Follow Thy Fair Sun a sixteenth century line by Thomas Campion, which follows with a wordplay on light and shadow
So it’s all explained, at least—when the sun is shining!
Noondial – the modern sundial that tells the time of Noon.
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