Peter,
A nice variant! A curved rotational surface can work as well as a flat one for
controlling the table. (My slight preference for the flat plane comes from the
fact that it is easier for me to make with the required smoothness.) The first
picture you posted appears to show that you have already incorporated a
longitude shift in the hour lines, so the sundial will display civil zone time
as opposed to local mean time.
This gets at what I really like about the use of a Poncet-type platform for a
horizontal dial: Three annoying corrections (equation of time, longitude shift,
and daylight-saving time) can be COMBINED into a single day-of-year setting of
a control arm. No mental arithmetic needed. When set to the right date, the
sundial simply reads the same time as a clock all day long.
This approach overcomes the three main reasons that a horizontal sundial has a
poor reputation for accuracy among the general public.
-- Roger
-----Original Message-----
Hi,
Here's the schematic view of my Poncet platform.
best wishes,
Peter
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