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). |