Bill Thayer wrote: > > Dear gnomonists and experts all, > > I've just put up a page -- no drawings, maps or figures yet -- on the > Horologium Augusti, the great sundial set up by Augustus in Rome using an > Egyptian obelisk as a gnomon: as viewed by Samuel Platner, the 1929 author > of a classic archaeological reference work, the Topography of Ancient Rome. > > I felt it necessary to comment on Platner's estimate of the size of the > pavement required for the dial face; and although I seem to get a > reasonable result, still have lingering fears I may have got my equations > wrong. (I am by no means an expert in astronomy.) > > Would those of you so *inclined* be so good as to check my page and let me > know what you think? It is at > <http://www.ukans.edu/history/index/europe/ancient_rome/E/Gazetteer/Periods/Roma > n/.Texts/secondary/PLATOP/Obeliscus_Augusti.html> > and the note in question is the blue dot at this (even longer) direct local > link: > <http://www.ukans.edu/history/index/europe/ancient_rome/E/Gazetteer/Periods/Roma > n/.Texts/secondary/PLATOP/Obeliscus_Augusti.html#refB> > > If those URLs are indigestible BTW to this e-mail message, the Horologium > page can be reached from the homepage of LacusCurtius (my signature below), > by clicking on the "Platner" link; then, on the Platner index page, on > "Obeliscus Augusti". > > Thanks in advance for any and all help (and please have no fear of finding > me easily offended by what will after all be my own ignorance). > > Bill Thayer > > LacusCurtius > http://www.ukans.edu/history/index/europe/ancient_rome/E/Roman
Dear Bill, It was hard to find the page but I succeeded. It also is hard to say what the dimensions of the dial of August were. Which part realy was constructed? Calculating an horizontal sundial for latitude 42 degrees with a gnomon of length g with antique hourlines you will need a plane as in the attached picture. Scale this to the real length of the obelisk and you have the real dimensions. But which part was contructed in real? As Buchner suggests it could have been the part as is inclosed in the red rectangle, much smaller then for a complete dial. The dial than only reads time from the start of the third hour until the end of the tenth hour and on the winter solstice only midday. Best wishes, Fer. Attachment converted: MAC Hard Disk:august.gif (GIFf/JVWR) (00014575)
