However, the method of simple differences introduce a 12 hour phase
error so we would be better off producing the differential dEOT/dt. As
the fourier approximation is linear this can be done with high school
calculus. I've included the differential function below. Luckily this
produces the
I have given this question quite a bit of thought over the past 3 years,
because the focusing sundial I sell is readable to a few seconds. It will not
live
up to its accuracy unless set properly.
If a dial is well made, and matched to its latitude, then it only has to be
levelled and
Gianni,
You wrote:
Because of these changes of the EOT from one year to the other it is
wrong,
in my
opinion, to use values very precise in calculating sundials. They may
be
useful to find the exact istant of the noon in a given day, etc.
I don't fully agree with your arguments.
If
Hank,
some years ago also I have obtained the Fourier approximation of the EOT
from its MEAN values on a 48 year period (from 2000 to 2047) ( I published
it in 2000)
The coefficients that I have found are practically equal to those found by
you and precisely:
t = 2 * pi * (j - 1) /
A few days ago I sent a fourier approximation for EOT including an equation
for calculating the day number of the year. Unfortunately I had hastily cut
and pasted the day-number formula from a web page that I had found. On
later checking I found that it didn't work properly - Oops.
Below I
At 06:59 AM 16/06/2003 +0200, you wrote:
Hank de Wit wrote:
However, the method of simple differences introduce a 12 hour phase error
so we would be better off producing the differential dEOT/dt. As the
fourier approximation is linear this can be done with high school
calculus. I've
Hello all,
This recent discussion has me wondering about some of the old dials in
Europe, and the declination lines on some of them. How well has the
precision of these lines held up over time?
Just for general discussion purposes, if I put a declination line for a
specific date on one of my
Hi Anselmo and others,
In your last message you mentioned other factors, like atmospheric,
refraction that might affect precision when setting or reading a sundial.
I've often wondered if there is a best time of day to set a sundial using
the Time method (as opposed to the compass, the Polaris,
