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Which way does the gnomon face on?
South
The gnomon, set to the correct latitude, has to point to the true South in the Southern hemisphere as in the Northern Hemisphere it has to point to the true North. The hour numbers also run in opposite directions, so on a horizontal dial they run anticlockwise (US: counterclockwise) rather than clockwise.
What angle should a gnomon be?
90°
Projection of the equatorial dial to form the ellipse of the vertical dial. The gnomon of the vertical sundial makes an angle of 90°–L with the vertical (that is, an angle L with the horizontal), as shown in the side view in Figure 5. In the southern hemisphere, the vertical dial is north-facing.
Why does the gnomon need to point north?
Celestial Pole: the points on the celestial sphere where it meets the Earth’s axis. The stars appear to rotate around these poles. To accurately tell time, the gnomon of a horizontal sundial must be parallel to the earth’s axis and therefore must point directly to the celestial pole.
Where does the gnomon point?
The pointy bit of a sundial is called a ‘gnomon’. It is the part that casts the shadow and in the northern hemisphere it points south.
Which way should a sundial face?
Sundials need to point in the direction of True North, and the style (either a sharp straight edge or thin rod, often located at the edge or tip of the gnomon) must be aligned with the Earth’s rotational axis.
How do you use a sundial compass?
Use a compass or look for the North Star at night to find true north. Then, rotate the face of your sundial until the gnomon, or the pin of the sundial, is pointing straight north. The 12:00 noon notation is aligned with the gnomon, so it will be pointing north as well.
Why is the gnomon on a sundial tilted?
When the earth rotates about its axis, the sun appears to “move” across the sky, causing objects to cast shadows. In a normal horizontal sundial, the base platform is kept steady, while the gnomon is moved to reflect the changes due to the earth’s axis tilt.
How do you find the True North of a sundial?
The traditional way of finding true North is to put a pole in the ground, make sure it is accurately vertical with a plumb line or spirit level on two sides at right angles, and then draw circles on the ground from the base of the pole.
What direction does a sundial have to point?
Direction of True North. Sundials need to point in the direction of True North, and the style (either a sharp straight edge or thin rod, often located at the edge or tip of the gnomon) must be aligned with the Earth’s rotational axis.
How do you use a gnomon on a sundial?
The gnomon is used to cast the shadow from the sun so you can determine the time of day. Adjust the gnomon until the tip points in the same direction as north based on your compass. The sundial will not tell the correct time unless the gnomon is facing north.
How do I know if my sundial is ready to use?
You should check the angle of your gnomon regardless of where it was purchased and is set up, just to be certain your sundial is ready to tell sun-time. A common method for checking the angle of the gnomon is to measure the angle with a protractor, and then crosscheck your measurement to ensure that the hour lines have been laid out correctly.
How do you find the shadow of noon on a sundial?
You will want to find a reliable method of marking the shadow at the instant of local noon. You can also position your sundial so that there is no shadow shown at high noon. The shadow should appear to the left in the morning, and to the right in the afternoon.