JMI EV-1cM Event Horizon Motorized Dual-Speed SCT Focuser

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JMI EV-1cM Event Horizon Motorized Dual-Speed SCT Focuser
Item # JM-EV1CM
  • The JMI Event Horizon EV-1cM is a motorized dual-speed 2" black-anodized aluminum focuser with rubber grip knobs that lifts up to 8 pounds, twice the weight of the EV-3c.
  • The Cassegrain version mounts on 6" to 16" Cassegrain telescopes (SCT & Mak-Cassegrain) with standard output threads.
  • The JMI Event Horizon EV-1cM includes SCT threaded output adapter allowing use of standard SCT accessories on output side of focuser.
  • 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 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.

One of the EV focuser modular bases is designed for Cassegrain telescopes. The most popular type of Cassegrain telescope is the Schmidt-Cassegrain Telescope (SCT). These telescopes achieve focus by moving the primary mirror. This design tends to create image shift which is especially problematic for CCD imaging. The EV Cassegrain focusers achieve focus by moving the eyepiece, camera or other equipment at the back of the telescope instead of the mirror.

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 motorized Cassegrain version is designed for use on 6" to 16" Cassegrain telescopes (e.g. SCT and Mak-Cas) with standard output threads. It includes an SCT threaded output adapter to allow use of standard SCT equipment on the output side of the focuser.

Although the EV-1cM can be plugged into the telescope's base allowing control from the Meade hand unit, you will have better control with the JMI hand unit. Our hand unit includes an electronic brake (not included in Meade systems), which stops the motor as soon as you quit pressing the keys, and linear voltage control for superior speed control. Also, older LX200 telescopes do not have enough power to properly run the motor on the low setting.

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: EV1CM

Additional Information

Additional Information

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

Customer Reviews 1 item(s)

I can't say enough about this product. Excellent quality, major improvement over stock focuser
1= Houston, We Have a Problem & 5= It's Out of This World
Review by Randall / (Posted on 10/26/2008)
Included Items

Included Items

  • JMI Event Horizon EV-1cM Motorized Dual Speed SCT Focuser
  • 1.25 SCT Threaded Adapter
  • Interchangeable Base
  • Integral Motor
  • Cord
  • Hand Control
Questions & Answers

Product Questions

The picture in the shopping guide page doesn't show the hand control. My question is how exactly, does it control the dual focus part of the unit. Both the main focus knob and the fine control knob must be controlled from the hand held part, but it isn't made clear just how? perhaps a picture of the hand control would help. Thanks.
Will this work with an EdgeHD 800 on a CGEM mount?
how much does it weigh?
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