JMI EV-1n Event Horizon Dual-Speed Newtonian Focuser

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JMI EV-1n Event Horizon Dual-Speed Newtonian Focuser
Item # JM-EV1N
  • The JMI Event Horizon EV-1n is a dual-speed 2" black-anodized aluminum focuser with rubber grip knobs that lifts up to 8 pounds, twice the weight of the EV-3n.
  • Newtonian version mounts onto a range of surfaces, from a tube that is 7.25" diameter or larger, to a flat surface.
  • The JMI Event Horizon EV-1n provides zero image shift, zero backlash, with tolerances that are 100X better than rack-and-pinion focusers!


What is the Event Horizon Focuser?

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 (see below) 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 modular design makes changes and upgrades extremely easy to accomplish. Add the optional variable-speed Motor and Smart Focus, Digital Read Out (DRO) or Digital Focus Counter (DFC), for the ultimate focusing system. The EV is truly a masterpiece of engineering and workmanship that you will be proud to own for years to come.

What is the Crayford Design?

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.

Event Horizon EV-1...

The Event Horizon EV-1 is a 2" black-anodized aluminum focuser with rubber grip knobs and two-speed operation. The focuser lifts up to 8 pounds. Manual controls are over 15 times and 1½ times finer than most rack-and-pinion focusers. 

The Newtonian version mounts on a range of surfaces from a 7.25" diameter, or larger, tube to a flat surface. The focuser gives 1/2" of travel and is designed for fine focus after rough adjustment with the normal telescope focusing knob.

The JMI Event Horizon EV-1 Features...

  • Sealed Stainless Steel Ball Drawtube and Drive Shaft Bearings
  • Carries Up To An Eight Pound Payload
  • 1.25" Eyepiece Adapter Included
  • Interchangeable Base
  • Modular, Black Anodized Aluminum Body Style
  • Knurled Aluminum Knobs
  • Surface-To-Surface Drive To Elminate Backlash
  • Modular Design For Easy Changes And Upgrades

JMI Product Number: EV1N

Additional Information

Additional Information

Manufacturer JMI
Focuser Design Crayford
Focuser or Mask Size 2" Drawtube
Focus Control Manual
Warranty 1 Year Warranty

Customer Reviews 1 item(s)

EV-1n focuser
I upgraded my 30-year old Coulter rack and pinion 1.25 with this JMI Crayford. What a beautiful piece of artwork! The feel and response of this focuser to my fingers is like slicing butter. Incredibly accurate and easy to mount, with plenty of options-I love the ability to be able to rotate the focuser right on the turret plate. Pricey-yes. But it is handmade and reasonable compared to what's on the market. I should have made this replacement years ago! Thanks, OPT, for being there for us little guys, too!
1= Houston, We Have a Problem & 5= It's Out of This World
Review by Tom / (Posted on 1/9/2013)
Included Items

Included Items

  • JMI Event Horizon EV-1n Dual-Speed Newtonian Focuser
  • 1.25" Adapter
  • Interchangeable Base
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Product Questions

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