Hello Jon, Mike Shaw wrote: <I do have one "non-interactive" one - an <equinoctial made by <Silas Higgon. <It uses two interchangeable specially shaped <gnomons, one <for use when the sun is travelling south, and the <other for <when it is heading back in my direction. <Adjustment is required on four days a year - at <each <solstice, and when the clocks change. It's not too <onerous.
As a rider to this you can, I believe, use only one gnomon and move the dial band at the solstices. You can then read the leading edge of the shadow during the time the sun is declining and the trailing edge when the sun is heading Mike's way once more. There will be a small error in only using one gnomon but no more than about 3 minutes which, I think, is quite acceptable. I hope to be making one soon for Singapore where there is no "summer time" to further complicate things. Silas Higgon www.sun-dials.net ----- Original Message ----- From: "Jon Noring" <[EMAIL PROTECTED]> To: <sundial@rrz.uni-koeln.de> Sent: Wednesday, October 16, 2002 5:53 AM Subject: New to sundials; interested in heliochronometers > Hello, > > For a while I've had an interest in sundials, but never explored that > interest in any detail. I recently decided to study it more closely, > at least whatever web-based resources I could locate. It is certainly > a fascinating topic -- and for some a real hobby to collect and/or > build sundials. > > Having a substantial solar energy R&D background (e.g., in the 1980's > I worked on solar central receiver power systems while at Sandia), I > can say that I actually understand (even after all these years) the > astronomical basis of the equations governing the position of the sun > in the sky, the Equation of Time (EoT), etc., and how to apply them > for terrestrial systems (e.g., solar central receiver systems must > know the precise location of the sun for directing the position of the > steerable heliostat mirrors.) > > Also, having a mechanical engineering background, one can say I am a > fanatic (read: "anal") on accuracy and precision. Thus, I have a stong > interest in sundials which can determine standard and/or local solar > time down to a minute or two (I believe these sundials are termed > "heliochronometers", am I right?) > > Doing a search, one intriguing (and surprisingly simple) design of a > heliochronometer is that built today by John Gunning (who I would not > be surprised is a member of this mailing list). For the very few here > who have not yet seen his web site, go to: > > http://www.dbweb.com/gunning.sundials/ > > Two more interesting heliochronometers are those made by Precision > Sundials: the Renaissance and the Sawyer Equant. See: > > http://www.precisionsundials.com/ > > I'd like to know of other designs for heliochronometers, historical > and current. And I'm especially intrigued to know of designs that do > not require any alignment interaction nor adding or subtracting minutes > to compensate for the EoT (the heliochronometers mentioned above are > "interactive", if I have that terminology right), and those which use > shadowing (besides the Sawyer Equant) rather than projection of the > solar disc using a pinhole (the Gunning) or using a mirror/prism (the > Renaissance.) > > (On a related topic, I assume a truly non-interactive heliochronometer > -- just "look and read" -- would have to come in two parts to cover > the two six month periods between solstices in order to compensate for > the variable EoT between the two periods -- literally two sundials > rather than one. In the deepest sense, therefore, there appears to be > no such thing as a truly non-interactive heliochronometer for year- > round use since one would at least need to know the month or season to > pick the right scale or sundial to use! -- definitely a form of > interaction. So what I term a "non-interactive heliochronometer" would > require one to at least know the season and accordingly pick the right > scale to read. Am I right here?) > > Anyway, I'd also like to know what books on sundials have very good > coverage of the history and design of heliochronometers. > > I have more questions, but will consider asking them at a future time. > I don't wish my introductory post to overwhelm the reader any more > than it must have already. > > Thanks! > > Jon Noring > > - > -
