Re: large sundial

[John Carmichael]

Hi everybody, Bill's right about the shadow's ":fuzz factor" being equal in both large & small dials and that both are equally accurate.  However, larger dials do have an advantage in that you can draw more minute lines onto the sundial face making it more precise. Have you ever tried to squeeze one minute timelines onto an eight inch dial face?  It's almost impossible.  Tony and I had this discussion awhile back, and wondered what was the smallest diameter dial face possible to make that would have one minute timelines?  We concluded that this depends on the dial face material, engraving (or painting)  process and tools used (line width). If I remember correctly, Tony said that his fine photoetching process could just barely do this on an eight inch (20 cm) bronze face. But with my carved stone sundials, I must have at least a 40 inch (100) cm face for one minute lines because if carve lines too close together, it weakens the stone. (and doesn't look good) The width of your timelines is most important in determining how many timelines you can squeeze in. If you have very wide lines, you can't draw as many. That's why Tony can't make a dial smaller than 8 inches with one min. lines because the width of a photoetched line can't be made smaller.  Maybe using the techniques that they use to make extremely fine lines on electronic silicon chips, you could make a tiny 1 inch sundial with one minute lines and use a magnifying glass to read it! John John L. Carmichael Jr. Sundial Sculptures 925 E. Foothills Dr. Tucson Arizona 85718 USA Tel: 520-696-1709 Email: [EMAIL PROTECTED] Website: <http://www.sundialsculptures.com> ----- Original Message ----- From: <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]> Cc: <sundial@rrz.uni-koeln.de> Sent: Tuesday, August 07, 2001 7:22 PM Subject: Re: large sundial > Well, all sundials (except rare focusing dials) cast a shadow whose blurred > edge is 2 minutes of time wide, corresponding to the 2 minute (of time) width > of the sun.  This effect is just more noticable in large dials, but does not > enhace or lessen their accuracy. > -Bill Gottesman, Burlington, VT > > In a message dated 8/7/2001 5:20:45 PM Eastern Daylight Time, > [EMAIL PROTECTED] writes: > > > Hi Alexei, hi all, > > > >  I think that an other problem of a large sundial, is the accuracy of the > >  shadow. Will the shadow be sufficiently "sharp" ? > > > >  Good luck and sunny skies ! > > > >  Alain MORY > >  48°N7°E