JMI Online Store
Event Horizon 2" Crayford Telescope Focusers

Home < Back

Product Index

Next Page >

Help


Product Index

EV 2" Focuser Models
EV-1
EV-2
EV-3

EV Focuser Options and Upgrades

EV Individual Parts

Related Products

Focuser Accessories

Design a Customized EV Focuser

EV-XT Focusers

Digital Readout

PC Focus Control

Smart Focus

Information Index

More Pictures

What is an EV Focuser?

What is the Crayford Design?

Customer Comments

Questions (FAQs)

Compare Models

Compare EV Models

Focuser Comparison Chart

Focuser Adapter Comparison Chart

Find What You Want

Find What We Sell for Your Equipment using the Telescope Equipment Index

Find What You Are Looking For using the Key Word Index

View Shopping Cart

Event Horizon 2" Crayford Telescope Focusers

 
EV-1n
Model 1
Newtonian Version
without Motor



EV1N
$359

Buy Now
EV-1nM
Model 1
Newtonian Version
with Motor



EV1NM
$519
Buy Now
EV-1c
Model 1
Cassegrain Version
without Motor



EV1C
$349
Buy Now
EV-1cM
Model 1
Cassegrain Version
with Motor



EV1CM
$509
Buy Now
EV-1r
Model 1
Refractor Version
without Motor



EV1R
$419

Buy Now
EV-1rM
Model 1
Refractor Version
with Motor



EV1RM
$579
Buy Now

EV-1 Telescope Focuser

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.  Dual-speed manual controls are over 15 times finer (small outer knob) and 1˝ times finer (large inner knob) than most rack-and-pinion focusers.  The two knobs have a 9:1 ratio.

The Newtonian version (EV-1n) mounts on a range of surfaces from a 7.25" diameter, or larger, tube to a flat surface.

The Cassegrain version (EV-1c) 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.  The focuser gives 1/2" of travel and is designed for fine focus after rough adjustment with the normal telescope focusing knob.

The Refractor version (EV-1r) mounts on many refractors having one of two different inside diameters of approximately 3.5" and 3.75".  The following is a partial list of refractors that should accept the focuser:

Celestron C4-R, C6-R, C6-RGT, Firstscope 102; Orion AstroView 100 EQ / 120ST EQ, SkyView Pro 120; Synta / Sky-Watcher Black Diamond 80 / 100 / 120, Evostar 80 / 90 / 120 / 150, (Pro Computerized) 100ED-EQ5P, 120ED-EQ5P, 120AR-EQ5P, 150AR-EQ5P, (Pro Manual) 102AR-EQ5M, (Pro Refractor OTAs) P80 ED-APO, P100 ED-APO, P120 ED-APO; Vixen ED100Sf

The Motorized version comes with a miniature motor and hand control unit.

See the Differences Between Models, the EV Options, the Focuser Accessories Page and the Focuser Comparison Chart.  For additional equipment see the Smart Focus and DRO products.  (Specify all options and accessories when ordering.)

NOTE

Meade
Telescope
Users

Although the EV-1c can be plugged into the telescope's base allowing control from a 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, some older LX200 telescopes do not have enough power to properly run the motor on the low setting.

The Event Horizon focuser has a totally modular design.  EV-1nM product code signifies a Model 1 with a Newtonian base and a motor.  The EV-1 includes a dual-speed drive with mechanical counter.  Click Here to view the product at different angles.  See our Focuser Comparison Chart for complete specifications.
 
An older version of the EV-1cM Mounted on a Meade ETX-LS 6" Scope
An older version of the EV-1r mounted on an Orion Refractor Telescope
EV-1r with drawtube extended

 

 
EV-2n
Model 2
Newtonian Version
without Motor



EV2N
$269

Buy Now
EV-2nM
Model 2
Newtonian Version
with Motor



EV2NM
$429
Buy Now

EV-2c
Model 2
Cassegrain Version
without Motor



EV2C
$259
Buy Now

EV-2cM
Model 2
Cassegrain Version
with Motor



EV2CM
$419
Buy Now

EV-2r
Model 2
Refractor Version
without Motor



EV2R
$329
Buy Now

EV-2rM
Model 2
Refractor Version
with Motor



EV2RM
$489
Buy Now

EV-2 Telescope Focuser

The Event Horizon EV-2 is a 2" black-anodized aluminum focuser with rubber grip knobs.  The focuser lifts up to 8 pounds.  Manual control is over 1˝ times finer than most rack-and-pinion focusers.

The Newtonian version (EV-2n) mounts on a range of surfaces from a 7.25" diameter, or larger, tube to a flat surface.

The Cassegrain version (EV-2c) 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.  The focuser gives 1/2" of travel and is designed for fine focus after rough adjustment with the normal telescope focusing knob.

The Refractor version (EV-2r) mounts on many refractors having one of two different inside diameters of approximately 3.5" and 3.75".  The following is a partial list of refractors that should accept the focuser:

Celestron C4-R, C6-R, C6-RGT, Firstscope 102; Orion AstroView 100 EQ / 120ST EQ, SkyView Pro 120; Synta / Sky-Watcher Black Diamond 80 / 100 / 120, Evostar 80 / 90 / 120 / 150, (Pro Computerized) 100ED-EQ5P, 120ED-EQ5P, 120AR-EQ5P, 150AR-EQ5P, (Pro Manual) 102AR-EQ5M, (Pro Refractor OTAs) P80 ED-APO, P100 ED-APO, P120 ED-APO; Vixen ED100Sf

The Motorized version comes with a miniature motor and hand control unit.

See the Differences Between Models, the EV Options, the Focuser Accessories Page and the Focuser Comparison Chart.  For additional equipment see the Smart Focus and DRO products.  (Specify all options and accessories when ordering.)

NOTE

Meade
Telescope
Users

Although the EV-2c 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.

This is a back view of the EV-2n which has a Newtonian base.  See our Purchasing Hints for a brief explanation of the differences between EV models and our Focuser Comparison Chart for complete specifications.
EV-2rM with drawtube extended

 

 
EV-3n
Model 3
Newtonian Version
without Motor



EV3N
$209

Buy Now
EV-3nM
Model 3
Newtonian Version
with Motor



EV3NM
$369
Buy Now
EV-3c
Model 3
Cassegrain Version
without Motor



EV3C
$199
Buy Now
EV-3cM
Model 3
Cassegrain Version
with Motor



EV3CM
$359
Buy Now
EV-3r
Model 3
Refractor Version
without Motor



EV3R
$269
Buy Now
EV-3rM
Model 3
Refractor Version
with Motor



EV3RM
$429
Buy Now

EV-3 Telescope Focuser

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 Newtonian version (EV-3n) mounts on a range of surfaces from a 7.25" diameter, or larger, tube to a flat surface.

The Cassegrain version (EV-3c) 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.  The focuser gives 1/2" of travel and is designed for fine focus after rough adjustment with the normal telescope focusing knob.

The Refractor version (EV-3r) mounts on many refractors having one of two different inside diameters of approximately 3.5" and 3.75".  The following is a partial list of refractors that should accept the focuser:

Celestron C4-R, C6-R, C6-RGT, Firstscope 102; Orion AstroView 100 EQ / 120ST EQ, SkyView Pro 120; Synta / Sky-Watcher Black Diamond 80 / 100 / 120, Evostar 80 / 90 / 120 / 150, (Pro Computerized) 100ED-EQ5P, 120ED-EQ5P, 120AR-EQ5P, 150AR-EQ5P, (Pro Manual) 102AR-EQ5M, (Pro Refractor OTAs) P80 ED-APO, P100 ED-APO, P120 ED-APO; Vixen ED100Sf

The Motorized version comes with a miniature motor and hand control unit.

See the Differences Between Models, the EV Options, the Focuser Accessories Page and the Focuser Comparison Chart.  For additional equipment see the Smart Focus and DRO products.  (Specify all options and accessories when ordering.)

NOTE

Meade
Telescope
Users

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.

This is a back view of an older version of the EV-3n.  The EV-3 economy Event Horizon focuser has the same quality as the EV-1 and EV-2 but fewer features.  See our Purchasing Hints for a brief explanation of the differences between EV models and our Focuser Comparison Chart for complete specifications.
This image shows an older version of the EV-3r Focuser on an Orion AstroView 100mm f/6.  The photo is courtesy of John Mills.
This image shows an older version of the EV-3r Focuser on an Orion AstroView 100mm f/6.  The photo is courtesy of John Mills.

 

 
EV-B
Model B
"Build-Your-Own"

Design ("Build")
your own focuser
on our website!

EVB
$Variable
Choose Options

EV-B Telescope Focuser

The Event Horizon EV-B is a "Build-Your-Own" version of our 2" black-anodized aluminum focuser.  It gives you complete flexibility in designing a focuser that fits your needs and desires.  Go to the Build-Your-Own page to build a code to use when ordering your special-order focuser.

NOTE

The Build-Your-Own version of the EV focuser allows you to design your own custom EV focuser which we will build to order.  If you were to exactly match one of the eighteen regular models* when picking options, the cost would be slightly higher ($30) since the build-your-own version is more costly for us to produce.  However, you have complete flexibility in creating a focuser that fits your needs and desires and may even be cheaper than our standard models.

* EV-1c, EV-1cM, EV-1n, EV-1nM, EV-1r, EV-1rM, EV-2c, EV-2cM, EV-2n, EV-2nM, EV-2r, EV-2rM, EV-3c, EV-3cM, EV-3n, EV-3nM, EV-3r, EV-3rM

 


Event Horizon Telescope Focuser Options and Upgrades

 
Upgrade to EV-1
JMI EV-3 or EV-2 Focuser
(after-purchase upgrade to EV-1 Focuser)



EVUPG1
$199
Buy Now

Upgrade any EV-3 or EV-2 to an EV-1 Focuser

JMI EV-2n, EV-2nM, EV-2c, EV-2cM, EV-2r, EV-2rM, EV-3n, EV-3nM, EV-3c, EV-3cM, EV-3r, EV-3rM

To upgrade, simply remove the old drive block and install this new one.  The upgrade includes the following individual parts:

1)  Dual-speed Drive with Dial Indicator
2)  Pusher Bearing
3)  Rubber-gripped Gold Knobs
4)  7/64" Hex Wrench
5)  Instructions for safely swapping the drive system

NOTE

This part number is designed to simplify (and reduce the price of) upgrading to our top-of-the-line EV-1 Event Horizon Focuser by avoiding the confusion involved in having to picking the right individual parts.  (The Dual-speed Drive requires Rubber-gripped Gold Knobs.  It cannot be combined with the Knurled-Aluminum Silver Knobs.  The Pusher Bearing is also recommended for this model focuser.)

 
EV-75 Upgrade
For Meade LXD75
SN-6, SN-8 or SN-10
 (at the time of purchase only)
SEE NOTE 2



EVUPG75
$89
Buy Now

EV-75 Upgrade for Meade LXD75 SN-6 / SN-8 / SN-10

Meade LXD55 SN-6 / SN-8 / SN-10, LXD75 SN-6 / SN-8 / SN-10

The EV-75 Upgrade makes the following changes to an EV-1n, EV-2n or EV-3n (Newtonian) focuser to prepare it to replace the stock focuser on the Meade Schmidt-Newtonian:

1)  Add an Adapter (EV-ADPT5) to the standard Newtonian Base.
     The adapter is made specifically for the SN-6 / SN-8 / SN-10.

2)  Change the Drawtube from 3" to 2.5" length.

3)  Add a 2" diameter x 2.13" height Enhanced Extension Tube (ADPT2X2.1E).

4)  Upgrade the 1.25" Eyepiece Adapter to a Combination 1.25" Eyepiece and
     T-thread Adapter (ADPT2-1.25T).

NOTE 2:  The Event Horizon focuser can only be upgraded for the listed price at the time of purchase.  For aftermarket upgrades, please purchase the following four individual parts:

Base Adapter EV-ADPT5
2.5" Drawtube EV-DT25
Extension Tube ADPT2X2.1E
T-thread Adapter ADPT2-1.25T

EV-75 Upgrade Base Adapter

 


Event Horizon Telescope Focuser Individual Parts

 
Standard Body
Individual EV Part



EV-BODY
$76
Buy Now
Newtonian Base
Individual EV Part



EV-BASN
$66
Buy Now
Cassegrain Base
Individual EV Part
(2" diameter thread)



EV-BASC
$61
Buy Now
Large-Format
Cassegrain Base
Individual EV Part
(3.25" diameter thread)
SEE NOTE 3



EV-BASL
$77
Buy Now
Extra-Large- Format Cass. Base
Individual EV Part
(4" diameter thread)



EV-BASX
$98
Buy Now
Refractor Base
Individual EV Part



EV-BASR
$109
Buy Now
Explorer Scientific
Version 1 Focuser Base for ED127
Individual EV Part
(ES Version 1)



EV-BASES
$56
Buy Now
See Explorer Scientific Focuser Version Information Here
Lunt Solar Base
for Lunt LS60T Ha
Individual EV Part
(LS60T H-alpha
and ES Version 2))



EV-BASLS
$56
Buy Now
See Explorer Scientific Focuser Version Information Here
Astro-Tech RC Base for M90x1 Visual Back Threads
Individual EV Part



EV-BASRC
$98
Buy Now
Sky-Watcher Refractor Base
Individual EV Part
(Equinox, Orion Eon)




EV-BASSR
$88
Buy Now
Base Adapter for Meade LXD75 SN
Individual EV Part



EV-ADPT5
$50
Buy Now
2.0" Drawtube
Individual EV Part
(2.0" Length)



EV-DT20
$34
Buy Now
2.5" Drawtube
Individual EV Part
(2.5" Length)



EV-DT25
$36
Buy Now
3.0" Drawtube
Individual EV Part
(3.0" Length)



EV-DT30
$39
Buy Now
4.6" Drawtube
Individual EV Part
(4.6" Length)



EV-DT46
$44
Buy Now
5.75" Drawtube
Individual EV Part
(5.75" Length)



EV-DT57
$50
Buy Now
Dual-Speed Drive
Individual EV Part
SEE NOTE 4



EV-DRVD
$124
Buy Now
Single-Speed Drive
Individual EV Part
SEE NOTE 4



EV-DRVS
$34
Buy Now
Pusher Bearing
Individual EV Part
SEE NOTE 4

ev_push.jpg (23266 bytes)

EV-PUSH
$33
Buy Now
Rubber-Gripped
Gold Knobs
Individual EV Part
SEE NOTE 4



EV-KNBR
$52
Buy Now
Knurled-Aluminum
Silver Knobs
Individual EV Part
SEE NOTE 4



EV-KNBA
$19
Buy Now
Motor
Individual EV Part
(Includes Hand Unit and Cable)



EV-MTR
$170
Buy Now

EV Telescope Focuser Individual Parts

The replacement or ad-on parts may be purchased individually.  If you wish to design your own focuser, please go to to the Build-Your-Own page to build a code to use when ordering your special-order EV-B "Build-Your-Own" focuser.  See EV-75 Upgrade above for upgrading a Newtonian EV Focuser for an LXD75 Schmidt-Newtonian scope.  The following individual parts are available:

Body

Base, Newtonian
Base, Cassegrain (2" diameter thread)
Base, Large-Format Cassegrain (3.25" diameter thread)
Base, Extra-Large-Format Cassegrain (4" diameter thread)
Base, Refractor (for approximately 3.5" and 3.75" inside diameter of telescope tube)
Base, Explorer Scientific ED127 (Explorer Scientific Version 1)
Base, Lunt Solar Systems LS60T Ha and Explorer Scientific Version 2
Base, Astro-Tech Richey-Chrétien astrograph (M90x1 threads)
Base, Sky-Watcher Refractor (Equinox, Orion Eon)

Base Adapter, LXD75 Schmidt-Newtonian

Drawtube, 2.0" length
Drawtube, 2.5" length
Drawtube, 3.0" length
Drawtube, 4.6" length
Drawtube, 5.75" length

Drive, Dual Speed with Dial Indicator (10:1 ratio)  See note 4
Drive, Single Speed  See Note 4

Pusher Bearing  See Note 4

Knob, Rubber-Gripped Gold  See Note 4
Knob, Knurled-Aluminum Silver  See Note 4

Motor (The motor option comes with all necessary mounting hardware and a hand control unit.)

NOTE 3:  This adapter may be too loose on newer scopes.  We have seen a problem with Meade LX90 12" Telescopes and we are waiting to see if we run into this problem again.  If you have a question, call and ask for Steve.

NOTE 4:  If you are purchasing an after-market drive system, you must select:
1) The type of drive — Single Speed (EV-DRVS) or Dual Speed (EV-DRVD),
2) A pusher bearing, if desired (EV-PUSH) and,
3) The type of knobs — Knurled-Aluminum Silver (EV-KNBA) or Rubber-Gripped Gold (EV-KNBR)
since the drive is sold as a complete unit.  Please note that the Knurled-Aluminum Silver Knobs (EV-KNBA) are not available with the Dual-Speed Drive (EV-KNBA)

 


Click here to view the EV-1 at different angles!  See our Focuser Comparison Chart for complete specifications.
All EV focusers include a compression ring in the drawtube for holding eyepieces and accessories without scratching the equipment.  The adjusting screw presses against the ring which tightens around the eyepiece or accessory.
The drawtube lengths available for the EV Series focusers are (from left to right) 2", 2.5", 3", 4.6" and 5.75".  The standard lengths are 3" for the Newtonian versions (EV-#n) and 2.5" for the Cassegrain versions (EV-#c).  To specify a drawtube length other than the standard length, you must purchase the Build-Your-Own model.
Newtonian base with Weather-stripping
The EV-2cM is shown here with the encoder and hardware installed for a DRO system.  The DRO Hand Unit controller is connected to the motor and encoder assemblies on the focuser using a flat phone cable with phone connectors.  For a Smart Focus system, the Smart Focus hand unit (left) replaces the regular DRO hand unit (right).  (NOTE:  This focuser does not have the standard Event Horizon sticker attached.  To see the logo sticker, view the EV-1nM above.


What is an Event Horizon Telescope 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 or Digital Readout (DRO) 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.

Here are a few key features of the Event Horizon focusers:

  • Modular design makes purchasing and installing options and upgrades a snap

  • Purchase one of our regular models or buy a customized focuser using the Build-Your-Own option

  • Low profile with no unsightly springs

  • Zero image shift and zero backlash

  • Up to eight (8) pounds of lifting power

  • Brass clamping rings hold eyepieces and equipment without scratching

  • 48mm threads on 1-1/4" adapters

  • Your choice of plastic or brass locking screw for different locking characteristics

  • Miniature light-weight, high-torque motor the size of an AA battery (motorized version)

  • Small slender hand control (motorized version)

  • Transition between motorized and manual focusing with the twist of a thumbscrew (motorized version)

  • Dual-speed drive with counter (EV-1 model)

  • 16 times finer focus than most rack-and-pinion focusers (EV-1 model)

  • Available with Digital Readout (DRO) hand control

  • Available with Smart Focus for control from your PC (with encoders and positional display)

  • Available with PC Focus Control for control from your PC (without encoders or positional display)

  • Quality construction and just plain beautiful!

Please see the Focuser Comparison Chart.  Compare our focusers with cheaper Imports.


What is the Crayford Design?

The Crayford Eyepiece Mount (CEM) was invented  by John 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.  Mr. Wall, who chose not to patent his idea, continues to design and build Crayford Focusers.


Purchasing Hints

Here is a quick overview of the Event Horizon focuser models:

Differences Between Basic Event Horizon Models
Model Extra Features Notes
EV-1 Dual-Speed Drive
Pusher Bearing
Rubber-Gripped Gold Knobs
Includes a Fast Knob, a Slow Knob and a Position Indicator Dial
Pusher Bearings give more Lifting Power
EV-2 Pusher Bearing
Rubber-Gripped Gold Knobs
Pusher Bearings give more Lifting Power
EV-3 None Single-Speed Drive, No Pusher Bearing, Knurled-Aluminum Silver Knobs
EV-B Varies Features are Based on Options You Choose

Each focuser can be further classified by the type of base ("c" for Cassegrain, "n" for Newtonian or "r" for Refractor) and whether or not it includes a motor.  For example, a motorized EV-1 for an SCT would be model EV-1cM.  You can make even more choices in the specifications of your focuser by purchasing the Build-Your-Own model.  If you want more information on individual parts of an EV focuser, the Build-Your-Own page includes descriptions and pictures.  You can purchase Individual Parts above.

The following chart is for those wishing to replace an NGF focuser with the closest match in the Event Horizon series.

Converting NGF Part Numbers to the Best Match in the Event Horizon Models
NGF Model EV Model Notes
NGF-DX1(M) EV-1n(M) The EV version includes fast and slow gold rubber-gripped knobs, a position indicator dial and pusher bearings for more lifting power
NGF-DX2(M) EV-2n(M) The EV version includes single-speed gold rubber-gripped knobs and pusher bearings for more lifting power
NGF-DX3(M) EV-3n(M) The EV version Includes single-speed knurled-aluminum silver knobs
NGF-C EV-1cM
EV-2cM
Matches the NGF-C with Two-Speed Upgrade (NGF2SPEED)
Matches the NGF-C without Two-Speed Upgrade


Customer Comments

"I now have a dilemma, whether to fit the EV-2cM to my Takahashi Mewlon 180 or should I place it in a glass case on the mantelshelf as a contemporary display of fine American design, engineering and manufacturing.  It is so heartening to see that there are still some organizations producing such elegant, quality, functional and cost effective products after the shocking excesses of the financial institutions of Wall Street and other global financial centres.  If only they had kept the customer in focus as JMI does..."  (D. S.  04/14/2014)

"I just wanted to tell you, I have been an amateur astronomer for 20 years.  I just purchased my 8th focuser from you, the EV-2c for SCT telescopes.  Your quality machining and general design is truly far superior to all the other focusers I have seen and used.  The mega thumbscrew and the ability to have manual or motorized at the turn of a knob is absolutely fantastic.  This is the only rotating focuser I have ever used that rotates super smoothly AND actually stays put even with a very heavy imaging train!  Thank you so much."  (M. R.  07/2013)

"Thanks for turning out superb products, especially your Event Horizon focusers."  (S. S.)

"I am a retired Tool & Die Maker (28 yrs) and I am accustomed to making precision machines, etc.  The focuser which I bought from you is superb in all areas of fit and finish.  Keep up the great work!  (T. C.)

"Just received your Event Horizon Focuser - WOW - fit and finish were astronomical!!  Words can't describe how happy I am with your product.  I MEAN that!  Anyone who spends $$$ more on _______ is foolish.  THANK YOU all for a stellar product!  God Bless."  (K. C.)

"Product Report [on the EV-3r]:  Superb focuser fellas!  No doubt the best value in a refractor Crayford out there.  I'm so glad I didn't go for the import to save a paltry $30!  Solid, smooth, nice to look at, no slop.  Tech support with installation questions first rate.  Keep up the fine craftsmanship, ingenuity and value that JMI stands for."  (J. M.)

"I received my EV-3r focuser Saturday and am wholly impressed with it.  Thank you for the lovely engineering and attention to detail.  I'm absolutely convinced this focuser is the finest available, especially for the price - bar none!  (I've owned Moonlite, Feathertouch and GSO crayfords so I'm speaking from experience.)"  (J. M.)

"Based on the price, weight capacity and feedback from others, I decided to order the JMI..."  Online Cloudy Nights Telescope Reviews — JMI EV-1r Focuser  (Barry Etter)

"I got two great nights out with the scope and new [EV-2nM] focuser.  The difference is astounding.  It makes observing a real treat when you don't take so much time achieving a great, sharp view.  Also, it is nice to know the focuser feels the same no matter how low the temperatures get.  Thanks for your assistance."  (R. G.)

"The EV-2nM and enhanced extension tube are a fantastic upgrade from the stock focuser on my [telescope].  I had troubles getting the stock focuser to achieve a crisp focus because of image shift, backlash and vibration.  Those issues are all eliminated with this fine piece of equipment.  [I] only wish I had done the upgrade when I first got the telescope.  I'd have spent much more time observing and less frustration with trying to get the image focused.  [This is] a truly fine product and [your are] great people to deal with."

"My experience with your company has, to say the least, been outstanding.  I contacted you on Monday and spoke with helpful staff who conveyed a sense of both understanding my requirements and reassuring me that the item would arrive within the timeframe I needed.  A follow up call made to check progress was treated in the same friendly, knowledgeable way.  While I have not used the focuser outside yet (storms tonight), it mounted easily and took my accessories with ease.  I will be going to our clubs dark site this weekend and will put the unit through its paces.  Many thanks for upholding excellent customer care and providing the hobby with first class instruments.  Thanks.  (S. P.)

"[The EV focuser] is a thing of beauty!!  A wonderful addition to my SN 8".  Makes the scope look like a million bucks!  Thank you very much!  It has been a pleasure doing business with you!  And I plan to do business with you in the future.  A long time customer of JMI, Roger..."  (R. S.)

"I bought my EV-3n with a check, so I expected a delay but the focuser arrived well before I expected it.  The packing was great, the finish was beautiful, but there was a tiny "hitch" in the focuser movement that synched with the rotation of the knobs.  I called the office and was immediately put in touch with knowledgeable support (I work in support also - yours is top rate!) who gave me a suggestion to try and permitted me to undo the shaft box to inspect the shaft for more clues.  I found two tiny coincident gouges on either side of center, which had left two tiny scrims of metal on the shaft - not more than a few thousandths of an inch.  It may have been caused during shipping, although there wasn't any obvious damage to the box.  A little 1000 grit sandpaper on a flat stick and the problem is gone - I can't even tell where it was. Now the focuser works as well as it looks.  (T. F.)

"The EV-1n 2-inch motorized focuser I purchased from you was better than I had expected.  The ease of use was refreshing in these days of over complication.  I would certainly recommend this item to anyone considering the purchase of a motorized focuser."  (R. A. S.)

"I received my EV-2c focuser from you yesterday and immediately installed it on my C8 and took it outside for a test.  I must say that I am very pleased with its performance.  I think that this it the first time I have ever had my C8 in perfect focus.  Everything works to more than my expectations.  Thanks."  (R. G.)

"I got the focuser on Saturday and I have to tell you it is simply a work of art!  It installed easily and so far it seems to work great.  I have yet to get to try it out under dark skies but I am sure it is going to do the job.  One thing that impressed me was the absolute zero image shift while focusing.  I have never been able to get a real good collimation on this scope using my laser collimator.  As I rack the stock focuser in and out the laser dot moves quite a bit.  Not with the EV thought, it is rock steady.  The laser dot stays in one spot and doesn't move at all.  Great work!"  (D. C.)

"The quality of the workmanship on my new EV Focuser astonished me and was excellent.  It is so nice to get a piece of equipment made here and not in China."  (J. V. C.)

"I recently purchased a JMI EV [motorized focuser] for my [scope]...  The stock focuser is so sloppy and toy-like that precise focus really is not possible.  Hold the two in each of your hands (the EV and the stock focuser) and the difference is striking.  This is, hands down, the best upgrade I have made.  It makes a good scope great."  (R. G.)

"The EV-3n came in faster than I expected.  My first word when I opened the box was, WOW!  The quality and craftsmanship was far better than I expected.  Thank you JMI for building such quality gear for our telescopes.  I will be buying from you guys again."  (K. B.)

"I...note with pleasure that someone at last is manufacturing the Crayford Eyepiece Mount commercially.  I had no intentions of doing this myself...  I write to say, good luck in your venture and what better use could the new CEM be put than to grace your splendid range of well designed telescopes."  (J. Wall, Inventor of the C.E.M.)


Frequently Asked Questions (FAQ)


Q. Does JMI sell rack-and-pinion focusers?
A. No.  All of our focusers are based on the superior Crayford design.  They operate with friction between the drive roller and the drawtube created by high pressure.
   
Q. Can I add a Motor to my Event Horizon focuser at a later date?
A. Yes.  The EV focuser's modular design makes it simple to add or upgrade any options at a later date.  See EV Focuser Individual Parts.
   
Q. Can I easily change from motorized focusing to manual focusing?
A. Yes.  You can quickly and easily transition between motorized and manual focusing with the twist of a thumbscrew.
   
Q. Will an EV focuser work on my Meade Starfinder?
A. Yes.  There are two options available for EV focusers on a Meade Starfinder.  The Starfinder is equipped with a high profile focuser.  EV focusers are low profile.  We have a 4.6 inch drawtube designed for the Starfinder.  Another option is to use an extension tube with our standard low profile drawtubes.  The extension tube option is best if you plan on doing prime-focus photography because it allows you to go back and forth between visual and photographic focus without moving the primary mirror from its normal position.  A longer drawtube may also obstruct the light path inside the optical tube when at minimum height.

Generally, we would make the following recommendations when replacing the Meade Starfinder focuser based on the type of telescope you have:

Equatorial:  The 1.5" extension tube and two backup plates (optimal for both photographic and visual).
Dobsonian:  The optional 4.6" drawtube and two backup plates (optimal for visual only).

These two setups will work without relocating the secondary or the focuser positions, however, four new holes must be drilled for mounting the focuser.

NOTE:  Before purchasing, please measure the height of the original focuser when it is fully racked out to insure that the replacement drawtube length is correct.
   
Q. What is a Backup Plate?
A. A backup plate is a square flat or rounded piece of aluminum that can be bent to conform to the radius of a telescope optical tube.  It is designed to add support for a focuser when attached to a Sonotube (cardboard) or wood constructed optical tube.  Two backup plates are usually recommended for Sonotube mounting, one for the inside and one for the outside of the tube as a base for the focuser.
   
Q. What are leveling setscrews?
A. Leveling setscrews are installed in the base of EV focusers.  They give you the ability to collimate the focuser with respect to the optical light path.  Correct alignment is critical for optical quality.
   
Q. Can a DRO be installed on my EV focuser at a later date?
A. Yes.  The EV focuser's modular design makes it simple to add or upgrade any options at a later date.  See the DRO option.
   
Q. What is the difference between the Cassegrain version of the EV focuser and MOTOFOCUS for a Cassegrain telescope?
A. A MOTOFOCUS unit connects to the focusing knob and motorizes the normal focusing motion, which moves the primary mirror in and out.  The Cassegrain version o the EV focuser attaches to the back of the telescope allowing you to focus without moving the mirror, thus eliminating image shift caused by a shifting mirror.  Initial rough focus can be achieved by use of the normal focusing knob (with or without MOTOFOCUS) with fine focus accomplished through the EV focuser.
   
Q. Will the Cassegrian verison of the EV focuser eliminate the problems I am having with image shift on my SCT?
A. Yes.  The EV-1c, EV-2c, EV-3c or EV-Bc is especially helpful when using a CCD camera.  This focuser is placed on the visual back and does not require the mirror to be moved in order to achieve focus.  Mirror movement in an SCT is what causes most of the image shift.
   
Q. How much back focus does the EV-1c, EV-2c or EV-3c focuser add to my SCT?
A. It will add 3.0" at its maximum extension.
   
Q. How much weight can the EV handle?
A. 8 lbs.  See our focuser comparison chart for more information.
   
Q. Do I need the Large Format Base with an EV-1c, EV-2c or EV-3c?
A. Large SCTs (10" or larger) come with an adapter to reduce the large (3.25" or 4" diameter) threads on the visual back to standard (2" diameter) size.  This adapter can be replaced by our Large Format Base to eliminate vignetting (obstructing the light cone).  This is beneficial for large format photography.