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 > > - > > - > -
