Grade 11 – Nautical Science

October 22, 2020

Parallax

The last correction to be applied is parallax.  So far the observer has been able to find the heavenly body’s centre above the horizontal plane.  All that is left is to allow for the earth’s radius.  In the drawing parallax is the angle OXC.  As you can see the true […]
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October 22, 2020

Total correction and true altitude

Total correction tables. The altitude correction tables for the sun are given at the beginning of the Nautical Almanac. They cover all altitudes from 0° to 90° and the heights of eye from 1 to 48 metres. The tables provide corrections to apply to both the upper and lower limbs […]
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October 22, 2020

Meridian passage

Introduction Meridian passage of an observed heavenly body, ie the sun, occurs when the body is directly over the observer’s meridian and the local hour angle (LHA) is zero. During this course we will only be covering the meridian passage (mer pass) of the sun. Those who wish to become […]
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October 22, 2020

Time of meridian passage

The local mean time (LMT) of mer pass on any meridian is obtained from the Nautical Almanac. At the bottom of the right hand page of the three-daily tables is a small table entitled “sun-mer pass”. The time of mer pass for the three days covered by the page is […]
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