How To Use A Sundial

A spot of light may be formed by allowing the sun s rays to pass through a small hole window oculus or by reflecting them from a small circular mirror. The gnomon will then be angled at 38 degrees. Turn the sundial until it is facing south use your compass to do this part.

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How to use your sundial.

How to use a sundial. A sundial will only work correctly when it s on a perfectly flat. When placing your garden sundial choose an open spot in full sun. Use the horizontal gray lines that are 10º apart to interpolate the altitude of the sun. Shadows point away from the sun.

You ll need to be able to turn the dial periodically to adjust it to the correct time. Place your sundial on a flat horizontal surface. One of the first time measuring devices the sundial has been in use for hundreds of years. The shadow slips past each of the hour lines rather like a clock hand.

Lay it on a level surface use a flat stone tree stump or a plinth designed specifically for sundials where it s convenient to view. Only the idea of using the sun to find the time is unfamiliar nowadays. The compass will not read correctly if the surface is uneven and without the compass working properly you will not be able to determine the time using the sundial. In bright sunshine the gnomon on the sundial casts a clear shadow which shows the time.

Make sure it lays level but don t attach it permanently. Pointing your sundial 1. In the illustration above the blue dots represent the tips of a sundial s shadow every 30 minutes on january 1 at 45ºn. Point the gnomon north if you re in the northern.

Use a protractor to adjust the angle by tilting the sundial plane 5 degrees and wedge it solidly in place. Place your new sundial in the sunshine making sure it is on something level. This may seem obvious but it s crucial. Given that sundials use light to indicate time a line of light may be formed by allowing the sun s rays through a thin slit or focusing them through a cylindrical lens.

Place the sundial compass on a level surface. It starts in the morning goes past 12 noon in the middle of the day and continues in the afternoon. Every hour mark the time and the position of the shadowing on the. Use the vertical arcs that are 10º apart to calculate the hour angle.

Make sure your sundial will be in direct sunlight all day. Now you can use the sun to tell what the time is. Place the sundial so the length of the blade of the gnomon is aligned with the earth s axis of rotation which is true north.