The three focusers
3-inch Self-Centering
A rack-and-pinion focuser with a self-centering compression ring that grips the drawtube evenly all the way around, a 9:1 reduction for fine focus and a 17 lb lifting capacity, built for heavy imaging trains. Because the ring presses evenly around the whole drawtube, the camera stays centered as it locks.
2-inch AR Series
A dual-speed focuser with 10:1 micro-focusing and adjustable drawtube tension, which comes with a 1.25-inch compression ring adapter.
APO EDT Series
A dual-speed 2-inch rack-and-pinion focuser with 10:1 micro-focusing and a 1.25-inch compression ring adapter. It takes 2-inch eyepieces and accessories.
What to look for
Fine focus: on a 10:1 dual-speed focuser, ten turns of the fine knob move the focus as far as one turn of the coarse knob, which makes the last step to sharp focus easy at high power. Load: a camera, corrector and filter weigh more than an eyepiece, so the drawtube has to hold them without slipping or rotating. Fit: the AR and APO EDT focusers are made for those Explore Scientific telescopes.
Frequently Asked Questions
Will these fit my telescope?
The AR Series and APO EDT focusers are made for those Explore Scientific telescopes. Check the fit on each product page before ordering.
Why upgrade a focuser?
For imaging. A focuser that shifts or rotates under a camera's weight loses the focus, and the 3-inch model is rated to lift 17 lb.
What does 10:1 mean?
Ten turns of the fine focus knob move the focus as far as one turn of the coarse knob.
What is drawtube tension for?
Setting how firmly the drawtube moves, so a heavier eyepiece or camera does not slide out of focus. The 2-inch AR Series focuser has it adjustable.
For how focusers differ across three grades of refractor, read AR102 vs ED102 vs ED102-FCD100.