The vernier
20.07.2021
All Cassens & Plath sextants are equipped with a vernier, which enables a reading accuracy of one tenth of a degree or minute. The following example explains how to read the sextant's vernier correctly (larger images can be opened on the right side):
0° position
1° position
after an exact 360° turn of the vernier
Example for 0°39,7'
The upper line (with a dot) of the right-hand scale indicates the whole minute of the left scale. In this example 39'.
The decimal value is read from the right-hand scale where both scale lines form a line (in this example 7).