Chine reference (black)

• ‌An inclination of the sextant is recognised immediately
• For retrofitting
• For all Cassens & Plath sextants with full-view mirror

The vertical or rear sight reference is a glass prism that can be retrofitted.

When the sextant is tilted, the horizon line seen through the prism appears offset from the line seen directly.

The vertical reference is a glass prism. When the sextant is tilted, the horizon line seen through the prism appears offset from that seen directly. The measurement is correct if the line of sight passes through the field of view without a step/offset.