For a Sun sight, hold the sextant vertically and direct the sight line at the horizon directly below the Sun. After moving suitable shade glasses into the line of sight, move the index arm outward along the arc until the reflected image appears in the horizon glass near the direct view of the horizon. Rock the sextant slightly to the right and left to ensure it is perpendicular. As you rock the sextant, the image of the Sun appears to move in an arc, and you may have to turn slightly to prevent the image from moving off the horizon glass.

The sextant is vertical when the Sun appears at the bottom of the arc. This is the correct position formaking the observation. The Sun's reflected image appears at the center of the horizon glass; one half appears on the silvered part, and the other half appears on the clear part. Move the index arm with the drum or vernier slowly until the Sun appears to be resting exactly on the horizon, tangent to the lower limb. The novice observer needs practice to determine the exact point of tangency. Beginners often err by bringing the image down too far.

Some navigators get their most accurate observations by letting the body contact the horizon by its own motion, bringing it slightly below the horizon if rising, and above if setting. At the instant the horizon is tangent to the disk, the navigator notes the time. The sextant altitude is the uncorrected reading of the sextant.

• Parts and principle of the sextant - 2009-07-02 - 11:25:19
• Reducing Star Sights to a Fix - 2009-04-24 - 02:08:03
• Convert A Polaris Sight To Latitude - 2009-04-24 - 04:45:52
• Longitude at Meridian Passage - 2009-04-24 - 04:15:10
• Latitude at Meridian Passage - 2009-04-23 - 01:03:09
• Reducing A Planet Sight - 2009-04-23 - 12:37:29
• Reducing A Moon Sight - 2009-04-23 - 12:18:18
• Reducing A Sun Sight - 2009-04-23 - 11:56:15
• Celestial Body’s Amplitude - 2009-04-23 - 09:29:35
• Compass Error By Azimuth Of Polaris - 2009-04-23 - 09:11:02

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