The sighting mirror and peep sight in a compass When using a compass clinometer, the sighting mirror and peep sight work together to give accurate geological readings. 1. The peep sight helps you align perfectly with your target, like aiming a rifle at an outcrop 2. The sighting mirror lets you view the compass reading while still sighting your target, reducing errors and keeping your orientation true. Together, they ensure precise strike and dip measurements even under tough field conditions. A