JMI EV-XTnm 3" Motorized Extreme Focuser for Newtonian Telescopes
The Event Horizon Focuser (EV) is a low-profile, friction-drive focuser designed for both the amateur and professional market. The highly acclaimed Crayford design permits tolerances up to 100 times better than conventional rack-and-pinion focusers. Zero image shift and zero backlash makes it fantastic for visual and photographic work and a must for CCD imaging. The EV is truly a masterpiece of engineering and workmanship that you will be proud to own for years to come.
What is a Crayford Focuser?
The Crayford Eyepiece Mount (CEM) was invented by John ("Jack") Wall. The Crayford name comes from the Crayford Manor House Astronomical Society (UK) to which he belongs. The Crayford design uses high pressure on a metal drive shaft pressing against a metal drawtube which is held by bearings on the opposing side. This direct surface-to-surface drive mechanism eliminates backlash and shifting of the drawtube as seen in other designs such as the rack-and-pinion focuser and allows for very fine adjustments. JMI recognized the benefits of this design and was the first company to bring it to the amateur market in a commercial product.
The EV-XTn "Extreme" Focuser
The EV-XTn is a 3" black-anodized aluminum "Extreme" focuser designed for use on large Newtonian telescopes The Newtonian version includes a removable 10" radius curved base (or optional flat base).