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Primaluce Lab OnAxisLock 50.8mm Eyepiece Holder for 50.8mm Hybrid-Drive Focusers

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The OnAxisLock 50.8mm eyepiece holder for 50.8mm Hybrid-Drive focusers replaces the traditional eyepiece holder present in AIRY ED72, APO80 and ED90 apochromatic refractors focusers and lets you use all the 50.8mm diameter accessories.

OnAxisLock is the accessories locking system that, compared to the one using normal screw, offers a greater clamping force, avoiding any possible flexure (so it's perfect for astrophotography), it does not damage the connected accessory and it perfectly centers the optical axis of the telescope. All this thanks to a new locking device with double ring: just rotate manually the appropriate outer ring (designed to allow an easy grip, even with gloves) in order to obtain a perfect closure!

During use of heavy photographic instruments like DSLR or cooled CCD cameras (often with filter wheels ), it's crucial to avoid flexures when we insert them into the telescope's focuser. This also important for visual use using large mirror diagonals and wide field eyepieces (which are often very heavy).

That's why we designed the OnAxisLock eyepiece holder that replaces the classic screw with a locking ring system. This allows you to perfectly lock the inserted accessory by rotating the outer ring (red): a special double ring tightens internal accessories with an uniform pressure. The OnAxisLock eyepiece holder also allows you to keep perfectly aligned the accessories inserted in the focuser: so you will be sure that your camera's sensor will be perfectly centered with the optical axis of the telescope.

In order to connect this model to Hybrid-Drive 50,8mm focusers of AIRY ED72, APO80 and ED90 telescopes, simply unscrew the original 50,8mm eyepiece holder, then screw the OnAxisLock.

Left: 50,8m original eyepiece holder in the AIRY APO80 Hybrid-Drive focuser
Center: in order to install OnAxisLock, you need to unscrew the original eyepiece holder
Right: OnAxisLock 50,8mm eyepiece holder threaded to the 50,8mm Hybrid-Drive focuser

The Primaluce OnAxisLock 50,8mm eyepiece holder for 50,8mm Hybrid-Drive focusers replaces the traditional eyepiece holder in AIRY ED72, APO80 and ED90 apochromatic refractors focusers and lets you use all the 50.8mm diameter accessories.

The particular locking mechanism also prevents to ruin inserted accessory because the pressure is distributed uniformly in the barrel. With the classic screw closure the mechanical stress is instead brought on a small area and this can easily ruin the barrel.


The special design of the outer ring has been developed to allow you to lock the accessory with ease, even when wearing gloves. This way you can be sure to safely lock your CCD camera or your eyepiece even in bad weather conditions.

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