How do you read the number of degrees in a sextant scale?

How do you read the number of degrees in a sextant scale?

To read the number of degrees: Find the lines on the arc that are closest to the index line on the index arm. The index line is usually somewhere between two lines. The correct reading is usually that of the lower value, i.e., the line to the right of the index line.

How can you tell position by sextant?

hold the sextant in your right hand and look at the sea horizon. By moving the index arm, line up the real and mirror horizons so that both appear as a single straight line. Now, look at the scale. If it reads zero, there is no index error.

How does a sextant work?

All it is is a device that measures the angle between two objects. The sextant makes use of two mirrors. With this sextant, one of the mirrors ( mirror A in the diagram) is half-silvered, which allows some light to pass through. The angle between the two objects is then read off the scale.

What can a sextant tell you?

Sextant, instrument for determining the angle between the horizon and a celestial body such as the Sun, the Moon, or a star, used in celestial navigation to determine latitude and longitude.

When reading a marine sextant What do we mean if the reading is on the arc and off the Arc?

Navigation Sextant – Readings ON and OFF the arc The normal graduations of the arc, to the left of zero, extending from 0 to 130 degrees are referred to as ON the arc. To the right of 0 degrees, the graduations extend for few degrees and are referred to as OFF the arc.

What are the parts of a sextant?

The basic parts of a marine sextant are: main frame, on which all the parts are mounted; limb, on which graduations in degrees are marked; index arm, mounted in such a way as to pivot about the exact center of curvature of the limb; index mirror, mounted at the upper end of the index arm and perpendicular to the plane …

Can we plot ships position using sextant?

This is calculated by using the Zenith distance of the body, which we can get from the altitude of the body. The intersection of two such position lines brought to same time will give the ship’s position. And when you have mastered the art of fixing ship’s position by sextant, you can proudly own this quote.

How accurate is a sextant?

Most sextants also include a vernier on the worm dial that reads to 0.1 minute. Since 1 minute of error is about a nautical mile, the best possible accuracy of celestial navigation is about 0.1 nautical miles (200 m). At sea, results within several nautical miles, well within visual range, are acceptable.