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 - -
