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Re: Sundials

Hugo Mills <hugo-64@carfax.org.uk> writes:

> On Fri, Mar 04, 2005 at 10:37:17AM -0500, Lennart Sorensen wrote:
>> The sun does peak the same time every day, but it's only at noon exactly
>> if you are in the right place on the planet (for your time zone).  If
>> you are east or west of that the time will be off a bit, but it will
>> still be the same every day.  
>    Actually, that's not true. It varies quite a bit, as Martin
> said. Take a look at the Equation of Time[1]. The variation isn't
> anything like as much as the hour that Martin said -- it's about +/-
> 15 minutes over the year.  The reason it varies is (IIRC) to do with
> the fact that the Earth's orbit isn't circular.

That is true but a good sundial can compensate for this with a
specialy shaped rod or multiple scales (and you use the one at the tip
of the shadow).


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