I've had some questions about the Soda Can Dial and how to read it. Here's a diagram taken at 3pm local time, 7 Nov 2006, which may help. The current time is read at the intersection of the vertical line corresponding to 7 Nov and the shadow cast by the top of the dial.
The dial now includes the correction for refraction.
Brad
<<sodaCan (v2).png>>
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From: Lufkin, Brad (Mission Systems)
Sent: Wednesday, October 25, 2006 4:08 PM
To: Sundial Mailing List
Subject: Portable Dial Adjusted for EOT and DST
Here's what I call a Soda Can Dial, designed for my location (Washington, DC). To use, cut out along top, left, and right edges. Wrap tightly around a soda can and tape left and right edges (but allow free movement around can). Photo-copy gnomon onto a sheet of mylar. Wrap mylar around same soda can and tape (but allow mylar to rotate). To use, rotate mylar until one solid line falls along today's date. Position soda can on horizontal surface with today's date facing you. Rotate soda can until shadow from back solid line falls along front solid line. Read current time where shadow from top of dial intersects front solid line and timelines (timelines are for standard and dst; and for babylonian/italian hours).
I've generated dials with 10-minute timeline intervals and, with experience, these can be read to the nearest 2-3 minutes. Only adjustment not made is for atmospheric refraction, so time is off by 4-5 minutes at sunset/sunrise.
Brad
<< File: sodaCan.png >> << File: gnomon.png >>
sodaCan (v2).png
Description: sodaCan (v2).png
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