PRIMA LUCE LAB OnAxisLock2 1.25"

The PrimaLuceLab OnAxisLock2 1.25" is a double compression ring eyepiece holder which perfectly centres 1.25" eyepieces and accessories with no flexure, no scratches and no off-axis tilt.

Whether you are using eyepieces and diagonals for visual observation or precision astrophotography with 1.25" cameras, the OnAxisLock2 ensures a perfectly centred optical axis. Simply insert the OnAxisLock2 into a 2" drawtube, then rotate the outer ring clockwise to secure your gear in place.

Why a locking ring matters

When you insert a heavy camera, a filter wheel, or a large mirror diagonal into a focuser, the weakest point in the optical chain is often the accessory clamp. A traditional set screw applies all clamping force to a single contact point on the barrel. Under load, this causes micro-flexures that shift the focal plane and tilt the sensor relative to the optical axis. It also leaves pressure marks and scratches on expensive accessories.

The OnAxisLock2 solves this with a double compression ring mechanism. A single manual rotation of the outer ring simultaneously tightens two internal rings that grip the inserted barrel with uniform, 360° pressure. The accessory is held firmly against any tilting movement, perfectly centered on the optical axis of the telescope.

The OnAxisLock2 1.25" fits any standard 2" / 50.8mm barrel, as found on many focusers. The outer ring has been designed with a deeply knurled grip that allows you to lock and unlock accessories with fingertip pressure. You do not need tools - you can operate it comfortably even when wearing gloves in cold conditions, and the tactile feedback of the ring lets you confirm the lock position without looking.

Specifications