Dear Chris, I confess: also I am not sure on the correctness of this sundial. My friend Riccardo Anselmi, have simulated each possibility of calculation of hours line, the inclination, the latitude etc., and also him have conclused that this is a mistake sundial! But him and I, are wonder on the fact that in the XVIIIth century (eBay not existed for fortune) were possible to do a incorrect sundial in a beautifull garden like this. Today we can see very much mistake sundials, but at the time of Ozanam, Rivard, De Celles...it is difficult for me to think someone would make a false sundial when she could have the best diallists of the world.
In any case, I am sure that the Triangula iron gnomon is not original and it was take from the second iron sundial in the Villa; I am not sure on the precision of the lecture on the hours line, but to see the position of the sun and the posizion of the sundial, it seems to me that is possible to read the hour with a approximation of 10 min. But this chek is not good because the gnomon is incorrect. The sundial was in good position respect to point N-S-W-E The north is at the top of the 12 hour line. Also I think it should be also possibile that the original sundial was a "equatorial", but the hours line are not right. Your suggestions are good, but the "mistery" of this sundial for now remain! Thanks Nicola ---------- Initial Header ----------- >From : "Chris Lusby Taylor" [EMAIL PROTECTED] To : [EMAIL PROTECTED],"Frank.King" [EMAIL PROTECTED] Cc : "sundial" [EMAIL PROTECTED] Date : Tue, 26 Aug 2008 14:23:39 +0100 Subject : Re: Ravello Sundial > Dear Nicola, > May I offer my thoughts? You're not going to like them. > > If you look carefully at the photographs that show the side of the sundial, > it is clear that the stone was quite deliberately made wedge-shaped, with an > angle of around 32 or 33 degrees. There is a border all round, and a carving > of an hourglass, similar to the form of the pedestal. The carving is > upright, so was deliberately made to be at 32/33 degrees to the dial face. > The triangular side faces were meant to be seen. The rectangular bottom face > was meant to be horizontal, as it is. We cannot blame the gardener. Whoever > made this dial intended it to be sloping at 32/33 degrees. 12 noon is at the > top, so it was intended to slope to the south, which is confirmed by the > compass rose - you can make out N, S and W. (You might query the validity of > a compass rose on a non-horizontal sundial, however.) > > I have taken the photographs of the dial face and stretched them (in > Photoshop) to make the dial appear circular in a square border. This might > be mistaken, but it certainly looks as though the dial is circular. > The foot of the gnomon should be on the line joining 6am and 6pm. It is. > > I then measured the hour line angles. I can't see any actual lines, so used > the centres of the numerals. They are, as nearly as I can see, all multiples > of 15 degrees. In other words, they are not hour lines for a horizontal > sundial (except at the North Pole) or for a sundial inclined at 32/33 > degrees (except at latitude 58/57 degrees). They are the hour lines of an > equatorial sundial. But an equatorial sundial would normally have its gnomon > central, not offset to the south as this one is. So my conclusion is that > this is a prototype of the pseudo-sundials we now see daily on eBay and in > garden centres. It looks like a sundial but is not really one. It was, I > suggest, made by someone who was aware that the sun goes 360 degrees in 24 > hours, but had no other idea how to position the hours on a sundial. > > Perhaps there once was a correct gnomon for this dial, sticking up at right > angles to it. The numerals go clockwise, so the gnomon would have to point > to the celestial North Pole. It could do so at latitude 58/57 degrees, with > the base horizontal, you might think. But then it would have to face north. > The 12 mark would be 12 midnight. The N mark would point south, not north. > > As for the gnomon, its style height is around 50 degrees, so it wouldn't > have been correct for the other, horizontal, dial either. This dial's > 9am/3pm lines seem to make an angle of around 40 degrees with the N-S axis. > This is correct for a horizontal sundial at 57 degrees North. Not 41 > degrees. Not even London. I wonder if it was bought in Scotland (the compass > rose initials are in English: N, S, E, W, not Italian). > > I'm a fan of Lord Grimthorpe's tower clocks, but have no idea if he knew > anything about sundials. I hope he wasn't responsible for this ghastly mess. > I am quite surprised you say it sometimes shows the time reasonably > accurately, as the gnomon is 40 degrees too steep and the hour lines are > hopeless (6am, noon and 6pm excepted!). > > ...or, perhaps, I've got it all wrong. > > Chris Lusby Taylor > 51.4N, 1.3W > > > > > ----- Original Message ----- > From: <[EMAIL PROTECTED]> > To: "Frank.King" <[EMAIL PROTECTED]> > Cc: "sundial" <[EMAIL PROTECTED]> > Sent: Tuesday, August 26, 2008 11:47 AM > Subject: Re: Ravello Sundial > > > > Dear Frank and friends, > > > > thanks for you comments. > > Yes this is a very curious (and unique) sundial. > > Like John Davis, also I and my friend Riccardo Anselmi, thinking the > sundial was setted for London or Irish latitude. > > The strange thing: on location, I have see that this strange sundial, > inclined, show the hours correctly! I cannot see the precision, but the > orientation is good. > > Only, I think the iron gnomon in this sundial is not the original. I > believe it was take from the second iron sundial present in the clouster, > dated 1720. > > The personal of Villa Cimbrone, not know about the second sundials! It was > swowed me only the inclined sundial in the Rose Garden! > > A thing is sure: the charm of this sundial live thogheter the charm of the > Villa Cimbrone and his incredible "Terrace of the Infinity". > > Nicola Severino > > > > > > ---------- Initial Header ----------- > > > > >From : "Frank King" [EMAIL PROTECTED] > > To : "[EMAIL PROTECTED]" [EMAIL PROTECTED] > > Cc : "sundial" [EMAIL PROTECTED], [EMAIL PROTECTED] > > Date : Tue, 26 Aug 2008 10:31:05 +0100 > > Subject : Re: Ravello Sundial > > > > > > > > > > > > > > > > > Dear Nicola, > > > > > > Thank you for your message. I enjoyed > > > your photographs of the dial that you saw > > > on vacation in Ravello: > > > > > > > http://gnomonices.blogspot.com/ > > > > > > You say that the dial appears to be marked > > > out correctly for a horizontal sundial at the > > > Latitude of London. > > > > > > Let me speculate... > > > > > > The gardens of the Villa Cimbrone in Ravello > > > were laid out by Lord Grimthorpe, who was a > > > noted Englishman in the mid-19th century. > > > > > > Lord Grimthorpe knew about many things (though > > > not always as well as he imagined). He certainly > > > knew about sundials and clocks. He designed the > > > Great Clock at Westminster which is incorrectly > > > referred to as Big Ben. > > > > > > It is possible that he had a favourite sundial > > > in London (latitude 51 deg 30') which he wanted > > > to set up in Ravello (latitude 40 deg 40'). > > > > > > This is a perfectly reasonable thing to do... > > > > > > You just prop up the south edge of the dial so > > > the dial plate, in Ravello, slopes downwards > > > to the north at an angle of 10 deg 50' to the > > > horizontal. > > > > > > I can imagine the instructions being misinterpreted > > > and the local gardener propped up the north edge > > > instead of the south edge. Also, he got the wrong > > > angle and propped it up by the latitude instead of > > > the *difference* in latitude. > > > > > > Of course, these mistakes would have the dial > > > sloping at 40 deg 40' which is a little more > > > than the slope in your photographs but I guess > > > this gardener wasn't very good at using a > > > protractor either :-) > > > > > > It is not uncommon to move a sundial... > > > > > > When the Royal Greenwich Observatory moved from > > > Hurstmonceux Castle to Cambridge they took a > > > sundial with them. They set this up on a > > > concrete platform which was inclined to the > > > horizontal by an angle of 1 deg 21'. This > > > (correctly) compensated for the change in > > > latitude. > > > > > > Sadly, the Observatory has now moved from > > > Cambridge but you can still see the concrete > > > platform. On Google Earth it is at: > > > > > > 52 deg 12' 53.80 N 0 deg 5' 45.57 E > > > > > > I hope this starts off a more serious discussion > > > about this curious sundial!! > > > > > > Best wishes > > > > > > Frank King > > > Cambridge, U.K. > > > > > > > > > > > > --------------------------------------------------- > > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > > --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
