JMI EV-3c Event Horizon SCT Focuser
What is the JMI Event Horizon Focuser?
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.
The Event Horizon EV-3 is a 2" black-anodized aluminum focuser with knurled knobs. The focuser lifts up to 4 pounds. Manual control is over 1???? times finer than most rack-and-pinion focusers.
The 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-3c 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-3 Features...
- Sealed Stainless Steel Ball Drawtube and Drive Shaft Bearings
- 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
Questions & AnswersAsk a Question
For a Meade LX200 10" OTA. Can I use the standard Meade F6.3 focal reducer with this SCT focuser?
For imaging, yes, especially if you are using a thin one-shot color CCD camera or mounting the reducer after the focuser for a DSLR. You will not be able to use both this focuser and an f/6.3 reducer in any visual configuration.