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Next Generation Focusers for Telescopes

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Next Generation 3" Crayford Focusers

Next Generation 1¼" Crayford Focusers

Next Generation Focuser Options

Related Products

Focuser Accessories
Information Index
What is an NGF?

What is a Crayford?

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Customer Comments

Questions (FAQs)

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Focuser Comparison Chart

Focuser Adapter Comparison Chart

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Next Generation 3" Crayford Focusers
 
NGF-XTn
 Model XT
Newtonian Version
without Motor



 NGFXTN
$512.00
 Buy Now
NGF-XTnM
 Model XT
Newtonian Version
with Motor
NGFXTNM
$652.00
 Buy Now
NGF-XTc
 Model XT
Cassegrain Version
without Motor



 NGFXTC
$512.00
 Buy Now
NGF-XTcM
 Model XT
Cassegrain Version
with Motor
NGFXTCM
$652.00
 Buy Now

NGF-XT

A 3" black-anodized (gold-anodized optional) aluminum "Extreme" focuser designed for use on large (10" to 16") Cassegrain Telescopes (NGF-XTc) with standard output threads and Newtonian Telescopes (NGF-XTn).  The Cassegrain version includes a 2" Eyepiece Adapter.  The Newtonian version includes a removable combination base (works on 10" radius up to a flat surface).  The manual version of the NGF-XT lifts up to 8+ pounds and the motorized version up to 18 pounds.  Manual "Nano Drive" control is approximately 13 times finer than most rack-and-pinion focusers.  Regular motorized versions include a standard hand unit.

See NGF Options, the SCT Accessories Diagram, the Focuser Comparison Chart and the Focuser Accessories Page.  For additional equipment see the Smart Focus and DRO products.  (Specify all options and accessories when ordering.)

NGF-XTn Newtonian version without motor, Part Number NGFXTN
NGF-XTn Newtonian version with motor, Part Number NGFXTNM
NGF-XTc Cassegrain version without motor, Part Number NGFXTC
NGF-XTc Cassegrain version with motor, Part Number NGFXTCM

NOTE

The NGF-XT requires a special modified 1.25" eyepiece adapter (call for details).  The included 2" adapter does not accept the thumbscrew in a normal 1.25" eyepiece adapter.

This picture shows the manual NGF-XTc focuser.  The "c" indicates that the focuser is designed for a Cassegrain telescope.
This picture shows the motorized NGF-XTnM focuser.  The "n" indicates that the focuser is designed for a Newtonian telescope.  The "M" indicates that the focuser is motorized.

 

 


Next Generation 1¼" Crayford Focusers
 
NGF-mini2
 Model mini2
Newtonian Version
without Motor



 NGFMIN2
$150.00
 Buy Now
NGF-mini2M
 Model mini2
Newtonian Version
with Motor
NGFMIN2M
$290.00
 Buy Now

NGF-mini2

A 1.25" black-anodized aluminum "Mini" focuser that lifts up to 4+ pounds.  Manual control is over 1½ times finer than most rack-and-pinion focusers.  The regular motorized version includes a standard hand unit.

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

Without motor, Part Number NGFMIN2
With motor, Part Number NGFMIN2M

NOTE The NGF-mini3 focuser is the same as the NGF-mini2 except for the drawtube bearings which allow the mini2 to lift more weight than the the mini3.

 

 
 
NGF-mini3
 Model mini3
Newtonian Version
without Motor



 NGFMIN3
$120.00
Buy Now
NGF-mini3M
 Model 2
Newtonian Version
with Motor

NGFMIN3M
$260.00
 Buy Now

 NGF-mini3

A 1.25" black-anodized aluminum "Mini" focuser that lifts up to 2+ pounds.  Manual control is over 1½ times finer than most rack-and-pinion focusers.  The regular motorized version includes a standard hand unit.

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

Without motor, Part Number NGFMIN3
With motor, Part Number NGFMIN3M

NOTE

When using a laser collimator, keep in mind that there will be slight deviations in the laser beam when moving the drawtube through the full length of travel.  This deviation is not noticeable visually, is only a small fraction of the amount present with a normal rack-and-pinion focuser and is completely eliminated with the higher quality of the other NGF focusers.

 The NGF-mini3 focuser is the same as the NGF-mini2 (pictured) except for the drawtube bearings which allow the mini2 to lift more weight than the the mini3.

 
NGF-miniC
 Model miniC
Cassegrain Version
without Motor



 NGFMINC
$150.00
 Buy Now
NGF-miniCM
 Model miniC
Cassegrain Version
with Motor
NGFMINCM
$290.00
 Buy Now

NGF-miniC

(The NGF-miniC and NGF-miniCM replace the NGF-miniS focuser.)

A 1.25" black-anodized aluminum "Mini" focuser designed for use on SCTs with standard output threads, as well as the Meade 7" Maksutov-Cassegrain telescopes.  Includes an SCT threaded output adapter to allow use of standard SCT equipment.  The NGF-miniC lifts up to 4+ pounds.  The regular motorized version includes a standard hand unit.

See NGF Options, the SCT Accessories Diagram, the Focuser Comparison Chart and the Focuser Accessories Page.  For additional equipment see the Smart Focus and DRO products.  (Specify all options and accessories and accessories when ordering.)

Without motor, Part Number NGFMINC
With motor, Part Number NGFMINCM

NOTE The NGF-miniCM is a 1-1/4" version of the NGF-CM but it allows more drawtube travel.  It also is designed for Cassegrain telescopes.
The NGF-miniS focuser (which has been replaced by the NGF-miniCM) is attached to a Coronado SolarMax 40 with the SCT threaded output adapter (included with the focuser).  Photo provided by Jarrett R. DuBois.

 


Next Generation Focuser Options
 
Flat Base
 NGF-mini2 / mini3 Base Machined Flat (at time of purchase only)



NGFFLATBASE
$10.00
 Buy Now

 Flat Base

Machine an NGF-mini2 or NGF-mini3 base to flat.  (The base cannot be upgraded after purchase because it is part of the focuser body and is machined and anodized before assembly.)

 

The NGF 3" 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.


What is a Next Generation Focuser?

The Next Generation Focuser (NGF) 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.  Add the optional variable-speed Motor and Smart Focus, Digital Read Out (DRO) or Digital Focus Counter (DFC), for the ultimate focusing system.  The NGF is truly a masterpiece of engineering and workmanship that you will be proud to own for years to come.

The NGF-XTc and NGF-miniC are specifically 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 NGF-miniC achieves focus by moving the eyepiece, camera or other equipment at the back of the telescope instead of the mirror.

Please see the Focuser Comparison Chart.


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.

Click on the picture to see one of J. Wall's original drawings.


Customer Comments

"Where did you get the great little motor?  Its the best little focuser.  Everything went together very easy.  All worked great.  Now I need a motor for my new ..."  (R. L. B.)

"I'm sure you have heard this before but I don't mind saying it again.  Your focusers are beautiful ! ! !"  (J. P.)

"My NGF-DX1 arrived the other day and everything was exactly as I had specified.  It is a fine example of superb workmanship and now my Nagler oculars are very happy!"  (J. L.)

"BTW, my 'scope is a pleasure to use with the new focuser.  Great product and great service.  Can't ask for more."  (P. L.)

"I am very impressed with the quality of the NGF focuser I purchased.  As a qualified first class machinist, I can appreciate the quality much more than most.  I am impressed, and that is no easy task.  (P. N. C.)

"I installed the [NGF-CM] yesterday and tested it out.  What a beautiful piece of engineering.  It's my second JMI focuser.  I have an NGF-DX1 on my homebuilt 18 inch dob.  You guys make great products!  Thanks again and Merry Christmas!"  (D. D.)

"I received the focuser—WOW, what a beautiful piece of machinery!  ...  You make a great product..."  (S. H.)

"Many thanks for the NGF-DX2 focuser which arrived safely.  I have to say I'm blown away by its quality and presentation.  ...  The foam contoured container is really something extra.  It is always a little daunting purchasing astro items from a picture in a magazine, especially flat black colored items.  The engineering and finish is excellent."  (P. W.)

"The [NGF] focuser [with Smart Focus] has made focusing more precise and infinitely easier, a very fine product!"  (Tony Hallas)

"It is marvelous to find that there still exist manufacturers of fine instruments that are capable of lasting a lifetime (longer, indeed, than many of the telescopes they are fitted to, I suspect) and are made to a superb level of precision and finish.  And you also obviously care about your customers and their satisfaction!"  (A. D.)

"[I] just returned from vacation and collected my JMI focuser.  It is superb!  Thanks for [your] very quick and efficient service.  I look forward to doing business again."  (J. A. O.)

"I recently purchased a deluxe NGF focuser unit for my LXD55 10" telescope.  Just today I received the motor upgrade kit and installed it.  It works great!  JMI, IMHO [in my humble opinion], makes one of the finest focuser upgrades for the money in this niche market today."  (J. P.)

"JMI provided the perfect solution to a common problem with [my] telescope.  The slide tube focusing arrangement that is standard equipment on [the refractor] proved to be somewhat problematic for people with different vision, especially eyeglass wearers.  JMI stepped in with a solution.  The NGF-miniS focuser..., outfitted with a 2" drawtube, proved to be the perfect solution to the focusing annoyance.  Lightweight and quality crafted, the motorized miniS works flawlessly for those fine tuning focusing problems.  Another great advantage is the ability to get a sharp focus quickly during imaging, no more loosening and sliding of the [refractor's] focuser!  My 'thanks' to Steve and the JMI crew for providing the perfect solution for my focusing problem."  (Jarrett R. DuBois)


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 NGF-XT, NGF-DX or NGF-mini focuser at a later date?
A. Yes, but you may need to return it to us for installation.  There is a small charge for any after-purchase installation or upgrade performed by us.  See Motor for JMI NGF Focusers in our JMI Catalog.
   
Q. What is a Backup Plate?
A. A backup plate is a square flat piece of aluminum that can be bent to conform to the radius of a telescope optical tube.  It is designed to add support for an NGF focuser when attached to a Sonotube (cardboard) or wood constructed optical tube.  Two backup plates are usually recommended, one for the inside and one for the outside of the tube as a base for the focuser.
   
Q. What does "radius of base" mean?
A. The NGF-DX focusers have a radial (curved) surface machined into the bottom of the base to produce a better fit to your telescope optical tube.  A normal radius is 10" (20" diameter).   A 5" radius (10" diameter) is available for smaller telescopes.  The NGF-mini focusers have a 5" radius only.  We also have a flat base option for mounting the focuser on a flat surface.  If your telescope tube has a slightly different radius than the focuser, you can add black foam weather-stripping tape under part of the focuser to block stray light while keeping a professional appearance.
   
Q. What do I do if the radius doesn't match the curve of my telescope?
A. If your telescope tube has a slightly different radius than the focuser, you can add black foam weather-stripping tape under part of the focuser to block stray light while keeping a professional appearance (see diagram).

   
Q. What are leveling setscrews?
A. Leveling setscrews are installed in the base of the NGF-DX and NGF-mini 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 JMI focuser at a later date?
A. Yes.  The focuser will most likely have to be returned to us for installation of a Digital Read Out system.   There is a small charge for any after-purchase installation or upgrade performed by us.