How many degrees must the rear sight of a lensatic compass be opened to allow the floating dial to rotate freely?

To allow the floating dial of a lensatic compass to rotate freely, the rear sight must be opened to a specific angle that minimizes any potential obstruction while ensuring that the compass can function accurately. The correct angle for achieving this is 45 degrees.

At this angle, the rear sight creates optimal conditions for the floating dial to align with the magnetic north without interference. This ensures that users can read the compass accurately while taking a bearing. A wider opening, such as 90 degrees, would not be practical as it would not provide the necessary support and stabilization that the rear sight is intended to offer when aiming.

Understanding this operation is crucial for effectively utilizing a lensatic compass, especially in navigation and orienteering tasks.