Re: My Smiling Red Face

[John Carmichael]

Bill, I'm happy that someone atempted an error analysis of the undulating styles.  I'll be most happy with the dial if time tells us that it is only 1 minute off.   But like Bob Hough told me yesterday: It is what it is.   The ridged areas on the panels are copper tubing with circulating cold antifreeze. These ridges don't affect the shadow edge at all because they lie below the styles.  The styles are three sided flanges that hold the side panels together. If you look very closely at the photograph of the East style, you will see that what I've been calling the East Style is actually two parallel styles separated by only about 6 inches.  Each corner of the flange is a style.  This creates an additional little style shift at High Noon because at High Noon, one style of the flange is directly above the other style.  At High Noon, the style shifts from the bottom flange corner to the top corner of the flange. But the since the distance  between the two styles is so small (6"), we saw no visible increase in the width of the penumbra.   We did see huge penumbra width changes within the space of about a minute when we had the big morning and afternoon shifts.  When these styles shifted the shadow velocity immediately changed and the spacing between the time points changes proportionately.     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: William S. Maddux To: sundial@rrz.uni-koeln.de Sent: Wednesday, June 26, 2002 6:36 AM Subject: My Smiling Red Face   John,   I am happy (though embarrassed) to report that I am now convinced that most of the edge problems I saw in the proposal photos were apparently artifacts.  They seem to have been introduced into the PDF images by the compression/decompression processes.  Perhaps some spatial periodicity aliasing was at work. There are suspiciously  moire-like patterns in panel areas, as well as less regular changes somehow introduced at the apparent edges.   However, this doesn't alter the bases for the calculation of time-error vs edge-error that I posted on June 25th. Photos did not enter into that:   >... Thus at that distance, the time required for the 1/2° degree >wide sun to pass through the meridian plane would be very >nearly 2 minutes of time during which it would move >about 9.3 inches relative to the style edge.  Therefore, if the >style's edge were to be laterally displaced 3 inches, the >resulting error in time would be about 3/9.3 x 120 = 38.7 seconds >of time, and a 1 inch wrong location of the effective edge would >cause nearly 13 seconds of error. ... .   which spoke to your comment:    > .....  By placing one eye at the base of a style, we could look >straight up the edge of the styles. We did see very slight >undulations in the styles, but we guesstimated that they were >only between I and 3 inches, a very small amount if you consider >the enormous size of the sundial. These could only affect the >precision of the dial by a few seconds.  Time will tell!   Indeed, time has already told me some things.   Continued best wishes for your endeavors,   Bill