Dear Mike & all, The most popular garden-center sundial around here is the armillary sphere. They always read local solar time. Stimulated by questions of (prospective) buyers, I once tried to write a fail-safe, fool-proof instruction for correct installation. There are differences with horizontal dials, of course, but most aspects are common to both. Therefore I would like to tell my doubts about the feasibility of such instructions.
I stopped my attempt, when I got frustrated by thoughts like: would any layman-reader be able to find his latitude, or even know what "latitude" means? Would he know how to measure and check an angle? Absolutely not trivial! But the most bothering aspect was: how to instruct setting the correct orientation? That aspect is missing from your 'golden five'. The pole-style, or gnomon sides in your case, should point to Polaris. Ever tried directly? The method I would use myself (after having checked the earlier aspects) is: calculate local solar time from clock time by taking latitude correction, EoT and DST into account, and turn the sundial until it reads local time. How to explain this procedure and its rationale unequivocally within 2-3 sentences? Providing insight in the relation between local and clock time is the more important, as the correctly oriented sundial will henceforth read local time. In Western Europe the difference with clock time is large, so that it is useless as a clock to the non-insider. Which makes the artistic quality the most important property to most people... I ended up with only a couple of hints on the Dutch version of my sundial site: - Don't take souvenir-type vertical dials from southern Europe back home - Check if the insertion point of the style is on the 6-18 hr line (for horizontal dials) - Are adequate instructions for installing and orienting the dial included? - Can it be fixed good enough so as not to serve as wind vane or merry-go-round? - Is the material weather-proof? - Doesn't it collect rain that turns into a swamp (except for the bird-bath type)? Have other list members experience with writing general instructions? Regards, Frans Maes ----- Original Message ----- From: "Mike Shaw" <[EMAIL PROTECTED]> To: "Sundial List" <sundial@uni-koeln.de> Sent: Friday, May 05, 2006 9:20 AM Subject: Buyer's Guide Fellow enthusiasts, I get really annoyed about the sundials that I see on sale in garden centres here in the UK. The people who make them seem to have no conception about how they work. As they are invariably horizontal dials, I thought I would put a "Buyer's Guide" to such dials on my web site. I think there are 5 golden rules - have I missed any? Check it out - follow the link from my home page. Helpful comments welcomed. Mike Shaw 53.37N 3.02W www.wiz.to/sundials ---------------------------------------------------------------------------- ---- > --------------------------------------------------- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
