Finding North

The final essential in sundial installation is to make sure gnomon is oriented north-south. Sounds easy and, with a little patience, it is.

One way, suitable for northern hemisphere, is to identify pole star. This is very close to projected position of earth's axis, about which sun and stars seem to revolve. You could mark direction from your sundial's location to pole star, but this method isn't quite accurate, and needs to be done in dark. And southern hemisphere doesn't have a pole star.

Method 2 uses a compass. Sounds pretty simple, doesn't it. But you guessed it - there are some complications.

Firstly, needle on a compass points to magnetic north, not true north, which is what we want. The difference between two is called magnetic declination, and is usually shown on good topographic maps. And while a simple addition or subtraction of difference between two norths should give you right direction, there may be some local magnetic effects which can't be compensated for.

The third method goes back to ancients - and there were some pretty smart operators around in old days.

You'll need a stick, some paper or board, a marker, a tape measure or long rule, a sunny day, and a bit of time on your hands. Set stick up vertically at location you have chosen for your sundial, so that top of its shadow falls on sheet of paper or board. If you stand with your back to sun, behind pole, set paper up so that morning shadow falls on its left hand side.

Now mark end of shadow with a permanent marker. Come back through day and mark new positions of tip of shadow - more often better. As day goes on, you'll notice marks form a curve.

Later in afternoon - any time after three is OK - connect marks you've made into smoothest curve you can manage. Do this while pole and paper are still in place. Then carefully measure distance between base of pole and curve. The shortest distance corresponds to true north. Mark it in some way, and align gnomon in same direction when you put your sundial in place.

You can find true north in other ways - again I suggest you try google as suggested above.

Once you have set up your sundial, check time, compensate for differences with your official time zone, pat yourself on back, and if sundial tells you it's after midday, pour a glass of your favourite beverage and put your feet up. Your time is now your own.