How does an SCT focus?

The focusing knob of an SCT is located off to the side of the primary mirror, and as it’s turned a rod pushes the mirror near its edge to displace it. However, the mirror itself is held near its center on a long baffle tube. So when the knob is turned, the mirror tilts slightly.

What does a focuser do?

The focuser moves the eyepiece holder up and down slightly, adjusting the focus of the eyepiece for each individual observer. There are friction focusers or rack-and-pinion focusers. Regardless of the type on your telescope, your focuser should move smoothly without causing your telescope to shake.

How does a telescope focuser work?

What is a helical focuser?

The very compact ZWO Helical Focuser allows for precise focusing of eyepices or cameras. It is ideal in conection with an off-axis-guider and a guide-camera. During focusing, the attached accessories keep their orientation and don’t rotate. The exact focus position can be fixed with a clamp screw.

Is the Crayford focuser for SCTs a joy to use?

This dual-speed Crayford focuser is a joy to use and you will wonder how you ever lived without it once you install it! By design, SCT Crayford focusers eliminate the annoying backlash and image-shift that plagues many SCTs. You will experience very smooth and precisely controlled focuser motion.

What kind of focuser do I need for a SCT?

Depending on your range of eyepieces and accessories, you may never need to touch your SCT’s main focuser again! The 2″ focuser barrel features a brass compression ring and can accept standard 2″ refractor-type diagonals and other 2″ accessories (Note that the use of this focuser converts your telescope’s rear SCT thread to a 2″ visual back.

Do you use the focus knob on the Crayford?

You first use your SCTs focusing knob to achieve coarse focus and then switch to the Crayford focuser for finer focus and control. Depending on your range of eyepieces and accessories, you may never need to touch your SCT’s main focuser again!

What does the thumbscrew do on a Crayford focuser?

The thumbscrew on the telescope side can be used to lock the focuser, allowing the use of heavy accessories or cameras without fear or slippage or losing focus. The other thumbscrew on the eyepiece end can be used to adjust the tension of the focuser to achieve a focusing “feel” that you like.