I have been fascinated
sundials since I was a child. I would often admire a dusty old sundial
in the corner of some public garden or stately home. I did not
investigate further until recently.
I was in the DIY centre, B&Q, recently and saw a large and
attractive ornamental garden sundial at a very good price, it was duly
snapped it up.
Once back home I tried to calibrate it at midday and then subsequently
tell the time. Unfortunately it did not seem to work. I then
realised when calibrating a sundial that midday is Local Midday at Sun
Time not GMT midday. So when it is midday in Greenwhich it is about
12:05 in Norwich and about 11:45 in Bristol.
This was not the only problem, the pointer, properly called the
gnomon, was actually misplaced by the sundial's designers so it had no
chance of telling the correct time. A little bit of re-engineering
and the dial was telling the correct local 'sun time', which was very
Essentially the designer had a mis-understanding of the design of a
sundial and had placed the base of the gnomon between the 9am and 3am
markings, right in the centre of this particular dial. This meant that
at 6pm the dial indicated that it was 3pm.
For the dial to function correctly it should have been placed between
the 6am and 6pm markings. Once the gnomon had been unscrewed and
from the face of the dial new holes were drilled in the dial face to
re-fix the gnomon in the correct position. Once this was done, the dial
performed more than adequately.
So a handy hint is that when purchasing your sundial, ensure that the
point at which the leading edge of the gnomon meets the face of the
is on a line that joins the 6am and 6pm markings, this will give the
dial a "fighting chance"!
There are other more scientific factors to be taken into consideration
too, I shall not go into them in too much detail, but there are a few
point which should be kept in mind. Take a look at page 2 to find out a