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):
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).