I used a string looped around the foci to lay out a 'human' analemmatic. I found that the string didn't stretch noticeably and you can hold the pencil upright well enough to get a more than adequate ellipse. Part of my goal was to lay out the entire dial, including the date scale and compensation for my westerly longitude, without using any measurements or calculations except for a protractor. No spreadsheet, no tables, no calculator, not even a ruler. Just a T square and a protractor to lay off the latitude for the eccentricity, the longitude (1 degree) and hours (15 degrees) on a circle around the ellipse, and the declination (23.4 degrees) and months (30 degrees) on a circle around the date scale. It was a great success. If anyone wants the full details of the method, please email me.
I thought of using a wire loop, but you'd have to use a very thin, bendy wire to get it to bend tightly around the pencil and to get all kinks out. The thinnest multistrand electrical cable, or something similar to what John uses for his wire gnomons (sold for clock weight hanging), would work best, I imagine. Chris Lusby Taylor 51.4N 1.3W John Carmichael wrote: > Use a wire or cable instead to avoid streching. > > 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: "Roger Bailey" <[EMAIL PROTECTED]> > To: <[email protected]> > Sent: Sunday, April 21, 2002 9:59 AM > Subject: RE: Spreadsheet for analemmatic sundials > > > Hello Richard, > > > > This is a good suggestion. Measuring two lengths is easier in the field > than > > trying to measure the perpendicular distances from the two axes. The > > distances from the center are already included in the spreadsheet as the > > polar coordinates for the points are calculated. The distance from the > > center is "r" in cells I25 to I45. The distance from the noon point where > > the hour ellipse crosses the N/S axis is easily calculated from the right > > angle triangle geometry as the square root of x squared plus (b-y) > squared. > > We will consider this change to the posted version. > > > > Another construction aid is included in the spreadsheet, the string loop > > length in cell G17 and the focal points "C" in cell G16. Peg the focal > > points at +/- c on the E/W axis. Take a loop of string equal to the length > > in cell G17 and loop it over both focal point pegs. Hold the string loop > > taught with a pencil or chalk in the other end of the loop. Use this to > lay > > out the hour ellipse. This is a great guide for constructing the dial but > > the string stretches and the pencil wobbles so this technique is not > > accurate enough to precisely locate the points. > > > > > > Roger Bailey > > Walking Shadow Designs > > N 51 W 115 > > > > -----Original Message----- > > From: [EMAIL PROTECTED] > > [mailto:[EMAIL PROTECTED] Behalf Of Richard Hollands > > Sent: April 21, 2002 8:17 AM > > To: [email protected] > > Subject: RE: Spreadsheet for analemmatic sundials > > > > > > > > Well I'm truly impressed with this spreadsheet though a little depressed > by > > it too - it's so professional. > > > > I have a suggestion. I've found it useful to included two extra columns > that > > give the distance from the hour point to the centre and to the noon point. > > Then you can use a very simple method of construction. Put a peg in the > > centre and noon points and attach one of those retractable steel tape > > measures to each peg. (A loop of string round bamboo pegs works well). > Then > > you retract or extend the two rules, one in each hand, with them crossed > > over in front of you while someone reads out the distances. All the hour > > points can be very quickly marked this way. > > > > Cheers, > > > > Richard > > > > - > > > > - > > > > - Content-Type: text/x-vcard; charset=us-ascii; name="Chris.Lusby.Taylor.vcf" Content-Transfer-Encoding: 7bit Content-Description: Card for Chris Lusby.Taylor Content-Disposition: attachment; filename="Chris.Lusby.Taylor.vcf" Attachment converted: Macintosh HD:Chris.Lusby.Taylor.vcf 2 (TEXT/ttxt) (000425EA)
