Sorry, folks. As always, Chris Lusby Taylor is right. And as usual I have egg on my face. I guess it’s a privilege to be mentored by such a precise and patient authority.
Back to the drawing board. Here’s my next proposal: Lay out a conventional analemmatic sundial turned through 180 degrees, i.e. with the noon marker to the south of the calendar line. Surround the sundial with a circular path, separated from the sundial by a circle of railings. At the appropriate point on the calendar line place a short upright pole which could be square in cross-section. Tell the visitor to walk around the circular path until his/her shadow falls in the direction of the pole. Read the time from the analemmatic hour mark on which the visitor’s shadow (not the shadow of the pole) falls. Cover the bottom few inches of the pole with the retro-reflective material sold by 3M for road traffic signs. Then, with luck, when the visitor stands on the right spot and views the pole from the same azimuth as the sun, the foot of the pole will appear to glow. This meets several of Mr Phillips’ desiderata. The principal hour markers will be on the southern side of the dial. He will get his circle or semi-circle. The dial will use a human gnomon. The pole must be moved each week along a north/south scale, but the scale itself could be fairly inconspicuous. Since visitors are not allowed to tread on the sundial face it can be planted tastefully - maybe in rows parallel to the driveway? Now shoot that one down! John Lynes --- On Thu, 26/6/08, Chris Lusby Taylor <[EMAIL PROTECTED]> wrote: > From: Chris Lusby Taylor <[EMAIL PROTECTED]> > Subject: Re: Advice wanted, on 'Analemmatic' sundial orientation > To: [email protected] > Date: Thursday, 26 June, 2008, 4:25 PM > I have now proved arithmetically (to my own satisfaction at > least) that > there is no dial shape that works like an analemmatic dial > but with the > azimuth halved. > > I did this by calculating how far the gnomon would have to > move at 2pm > between the solstices and the equinoxes, and comparing > these figures with > 4pm (for some arbitrary latitude). The ratios are > different, implying that > wherever you put a vertical gnomon on these three dates you > could not > position both a 2pm and a 4pm marker. For a normal > analemmatic dial the > ratios are all 1, i.e. the distance you move the gnomon > from winter to > spring = the distance you move it from spring to summer, > for all hours of > the day. > > Too bad. But I like the 2:1 gearing idea. Mechanisms to do > this are very > simple - the top of a pair of compasses is an example. > > Chris Lusby Taylor > 51.4N 1.3W > > -----Original Message-----From: > [EMAIL PROTECTED] > > [mailto:[EMAIL PROTECTED] > > > > Dear Sundial Experts, > > I have recently joined this Mailing List, and hope > that any members will > be > > able to give me some assistance on the following > situation. > > Our local Stately Home ("Kentwell Hall", > Long Melford, Suffolk) is > > considering installing an Analemmatic sundial, as a > new interactive > > attraction for visitors - but we are getting > 'conflicting' advice, on > > whether this 'Human Sundial' will work in the > way we want it to. We have > > been in discussion with "Modern Sunclocks" > (apparently the acknowledged > > 'experts' for these features), who have told > us that its central scale of > > dates must be aligned North/South - plus that hour > markers must be > correctly > > positioned on an elliptical ring, and which would lie > on the Northern side > > of that scale of dates. > > Photographs on their website ( www.sunclocks.com ) > confirm this. > > However, our 'Director of Operations' (Mr > Phillips) absolutelyINSISTS that > > he wants the scale to run exactly parallel with > ourmain driveway - on a > > compass bearing which is about 162 degreesfrom North, > with the hour points > > placed on its Southern side.He also wants the hour > points to form an exact > > semi-circle, andnot be elliptical in shape. Mr > Phillips refuses to accept > > thathe cannot arbitrarily position the Human Sundial > feature as hewishes, > > and says that it must be possible to create this so > thatit could then > align > > with the existing layout of buildings/paths. > > Can anyone on this Mailing List tell me whether it is > possible toinstall a > > Human Sundial to fit any existing orientations, > (withappropriate > > re-calculation of its component parts) - or, if > not,just confirm that it > > must be as "Modern Sunclocks" have told me. > > I can then show the 'weight of evidence' to Mr > Phillips. Because"Kentwell > > Hall" is a well-known Stately Home (open to the > public),we should not want > > to become a 'laughing stock' by installing > afeature which does not work - > > despite Mr Phillips assurance that"all types of > sundial can be adjusted to > > work, in any location". > > Looking forward to all comments (to this List, or sent > privately). > > Sincerely, Alison Shields. > > > > --------------------------------------------------- > > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > > --------------------------------------------------- > > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > > --------------------------------------------------- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > ______________________________________________________________________ > This email has been scanned by the MessageLabs Email > Security System. > For more information please visit > http://www.messagelabs.com/email > ______________________________________________________________________ --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
