>From Edley McKnight: >Hi Roger and all, > >Not ever having seen one, I'd imagined it as a horizontal slice through an >equatorial >dial, with the pivot on the gnomon and the sliding on the dial face, but this >looks >easier to adjust. I would imagine now that so long as the pivot point and the >inclined >plane contact points all start out in a horizontal triangle that it would >work. The inclined >plane appears to be parallel with the equatorial plane, yes?
Hi Edley, The pivot and contacts on the inclined plane don't *have* to define a horizontal plane, but they might as well, since they are being used to carry a horizontal sundial. Also, everything will be more stable that way. You're right, the inclined plane must be parallel to the plane of the celestial equator (and Earth's equator). Therebore, this original form of Poncet table works well at high and temperate latitudes. But when you get close to the Earth's equator (say, within the latitude band from 15 N to 15 S), the inclined plane would become so steep that it wouldn't support the table properly. -- Roger --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
