I'm afraid I can't give you any answers , but the original is in the Science Museum, London. They don't give any clues either, but I guess you could contact them https://collection.sciencemuseumgroup.org.uk/objects/co143/azimuth-sun-dial-simple-azimuth-sundial
Best wishes, Patrick Vyvyan On Mon, 25 Oct 2021 at 14:23, Steve Lelievre < [email protected]> wrote: > Hi, > > Today a website called Vermont Free Press published an appallingly > confusing (to me) summary of types of sundials. If you can bear to look, > it's at https://www.vermontpressbureau.com/types-of-sundials/ > > However, there was one thing about it that piqued my interest: the photo > of an azimuth sundial ( > https://www.vermontpressbureau.com/wp-content/uploads/2021/10/Azimuthal.jpg > ). > > From what I can make out, there is a metal flap at the end of the > alidade / sighting arm (the end at top in the photo). It must get turned > up to make a shadow-caster. I guess the arm has to be rotated so that > the shadow falls along it, and time is then read from where the > right-hand edge of the arm crosses the net of hour and declination > lines. But then, wouldn't the screws seen in the upper plate block the > arm from being turned to the required orientation? > > Another bit I can't figure is the little circular scale just north of > the centre of the dial, with the pointer. Perhaps just an Equation of > Time scale? Or perhaps a cam connects it to the arm so that it can be > used to set the arm's length? (The slot in the arm suggests it can be > slid in and out to set the tip at the applicable declination circle, > which is a nifty feature.) > > Cheers, > > Steve > > --------------------------------------------------- > https://lists.uni-koeln.de/mailman/listinfo/sundial > >
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