Uniglobe Manual Page 4

MEASUREMENT OF ANGLES IN THE PLANE

The measurement of angles is the basic concept required for definition of the celestial environment. Consider the circle shown in Figure 2. Our basic frame of reference in measuring angles is the circle. The circle is considered to be composed of 360 separate parts, each of which is called a DEGREE. Thus, the angle between A and B shown in Figure 2 is 15 divisions, or 15°. The symbol for a degree is °.

In Figure 3, the observer's eye can determine the angle between two objects, assuming that he has some type of measuring device. It is important to remember that the distances from the observer to the objects may be changed without affecting the angle: thus object A can be anywhere on the line through it and the observer and object B can be anywhere on the line through it and the observer.

Using the spanner, which is essentially a device for measuring angles, as shown in Figure 4, the angle between objects A and B can be determined with some accuracy. The use of the spanner involves the use of an angular scale which is different from the scale on the circle in that the linear distances between marks differ. The spanner is an arc of a circle with a radius of approximately 6 1/4 inches. The circle is of a radius of approximately 2 inches. However, the angles measured with either device are the same. To use the spanner, the observer's eye must be at a point 6 1/4 inches from the spanner. (At the center of the circle defined by the spanner). Angles in any plane can be measured by rotating the spanner.

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MEASUREMENT OF ANGLES IN THE PLANE The measurement of angles is the basic concept required for definition of the celestial environment. Consider the circle shown in Figure 2. Our basic frame of reference in measuring angles is the circle. The circle is considered to be composed of 360 separate parts, each of which is called a DEGREE. Thus, the angle between A and B shown in Figure 2 is 15 divisions, or 15°. The symbol for a degree is °.
	In Figure 3, the observer's eye can determine the angle between two objects, assuming that he has some type of measuring device. It is important to remember that the distances from the observer to the objects may be changed without affecting the angle: thus object A can be anywhere on the line through it and the observer and object B can be anywhere on the line through it and the observer.
Using the spanner, which is essentially a device for measuring angles, as shown in Figure 4, the angle between objects A and B can be determined with some accuracy. The use of the spanner involves the use of an angular scale which is different from the scale on the circle in that the linear distances between marks differ. The spanner is an arc of a circle with a radius of approximately 6 1/4 inches. The circle is of a radius of approximately 2 inches. However, the angles measured with either device are the same. To use the spanner, the observer's eye must be at a point 6 1/4 inches from the spanner. (At the center of the circle defined by the spanner). Angles in any plane can be measured by rotating the spanner.
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