OnAxisLock2 31,8mm eyepiece holder

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. 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.

A universal reducer for any standard focuser

OnAxisLock2 31.8mm eyepiece holder fits into any standard 50.8mm connection, including the most common focusers available on the market. No additional adapters required. It converts your 50.8mm connection to accept any 31.8mm accessory while maintaining the same rigid, repeatable mechanical interface.

For visual use and astrophotography

OnAxisLock2 is equally suited for visual and photographic use:

• Connect 31.8mm eyepieces and mirror diagonals or cameras without any wobble
• Use it with any focuser that has a standard 50.8mm connection, including those not made by PrimaLuceLab

The even pressure distribution also protects your accessories: the barrel is never scratched or deformed, even after years of use.

Easy to use, even in the dark

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.