Thanks for the information about the circumstances of the dial's time-reading.
One more thing I should mention: To azimuth-align the dial by adjusting it to say the time that it should say, it isn't necessary to interpolate the dial's time-reading. You could ask the relevant people at what approximate clock-times they'd like to consider azimuth-aligning the dial. Then you could calculate as follows: 1. Calculate what local true solar times correspond to those times that they mentioned. 2, Determine and choose what whole (integer) hour true solar times (or half-hour times, if the dial shows them and one of them is closer) are closest to those local true solar times that you calculated in paragraph #1 above. 3. Then calculate what clock-times correspond to those times chosen in paragraph #2 above. On a notebook-page, write down, on separate lines, each of the clock-times in paragraph #3 above, and next to it, on the same line, the local true solar times chosen in paragraph #2 above. Advise the relevant people to choose one of those listed clock-times, and, at that time, rotate the dial so that it shows the whole or half-hour local true solar time that is written next to it on the same line. -------------------------------- And it goes without saying that any dial-time and clock-time comparisons made for the purpose of calculating the azimuth-alignment error should be done at times when the dial-time is such that the shadow is exactly on an hour-line, half-hour line, quarter-hour line, 10-minute-line...or, in other words, some line on the dial-fact. In other words, you can and should choose a clock-time for the comparison, at which you aren't going to have to interpolate the dial-time. --------------------------------- One more thing: If two different clock-time/dial-time comparisons give different values for the azimuth-alignment error, then that suggests that the dial has more problems than just its azimuth-alignment. >From various points on the north and south edges of the equatorial band, measure the distance from the edge of the band to the center of the band-circle. ...to find out if the equatorial-band is circular and the gnomon is centered in it. Look at the dial from the side, using a T-square, to judge whether the gnomon is perpendicular to the edges of the equatorial-band. I'd expect that, if it's off enough to cause a 22.5 minute problem, the non-perpendicularity would be quite noticeable. Inexpensive Band-Equatorials, such as inexpensive Armillaries,always do terribly by these construction-standards. Out of round band, uncentered, non-perpendicular gnomon. Michael Ossipoff ... On Tue, Sep 25, 2018 at 9:26 PM Steve Lelievre < steve.lelievre.can...@gmail.com> wrote: > Yep, that's it. > > Steve > > On 2018-09-25 6:09 PM, Hank de Wit wrote: > > Is this the dial? > > > > > https://s3.amazonaws.com/gs-waymarking-images/4ac8dd87-b79b-42a0-9a14-08e86890c14d.JPG > > > https://c8.alamy.com/comp/AWRMGN/sun-dial-van-dusen-gardens-vancouver-bc-canada-AWRMGN.jpg > > > > --------------------------------------------------- > https://lists.uni-koeln.de/mailman/listinfo/sundial > >
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