Grade 11 – Nautical Science

October 20, 2020

Reading the sextant

Reading the sextant is very simple: Degrees are read directly from the graduated arc opposite the index mark on the index arm. Minutes are read from the micrometer drum opposite the vernier index mark. Seconds are read from the vernier where one of the vernier graduations lines up with one […]
Do you like it?0
0 Read more
October 20, 2020

Sextant errors and their correction

Adjustment screws. Every sextant is equipped with error adjustment screws.  The design of these screws varies from sextant to sextant.  Some have ordinary screw driver slots while others have round heads with a hole drilled through it.  The first requires the use of a suitable screw driver whilst the others […]
Do you like it?0
0 Read more
October 22, 2020

Introduction

Individual corrections. In order to be able to use the altitude obtained by sextant of a heavenly body, we need to convert it from a sextant altitude to a true altitude. To do this we need to apply five individual corrections to the altitude obtained from the sextant, namely corrections […]
Do you like it?0
0 Read more
October 22, 2020

Observed to true altitude

When we take a sextant altitude of a heavenly body, we measure the angle between the body and the visible sea horizon as witnessed from the observer’s position on the bridge of a vessel. (angle DOX in the diagram). This is referred to as the observed altitude. In converting it […]
Do you like it?0
0 Read more
Prev page
1234567891011121314151617181920212223
Next page