Hi diallers, I am considering a model cube dial with E. S and W faces, each with a concave hemisphere on it. It would have a pin gnomon with a ball nodus at the end, at the centre of the hemisphere. I understand that this is based in the Greek" hemicyclium" but there.are a few 16th century cube dials of this type in England and Scotland.
I've two questions, What are the dial equations for the hour- and day-curves for a hemicyclium-based dial? Do they require some spherical trigonometry? How' in practice, could I draw/paint/scribe etc the said curves onto the concave shapes? Your help would be appreciated, Phil Walker 52N2W (ish) http://www.sundial.pwp.blueyonder.co.uk/
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