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NGT-12.5 Product Information

NGT-12.5 Optional Upgrades

NGT-12.5 Optional Accessories

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Consider adding Focus Motor Controls, using your PC to the EV-1 or EV-2 focuser.

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12.5" NGT Telescope

12.5" Split-Ring Newtonian



NGT-12.5 Product Information  DISCONTINUED


• Open truss Newtonian

• Split-ring equatorial mount

• Rotating nose assembly

Built-in azimuth adjusting plate for easier polar alignment

• Compact size

• Fast one-man assembly

Removable ring assembly allows greater disassembly with the largest component weighing 40 lb.

Sidereal, Lunar, Solar and King tracking rates with both Northern and Southern hemisphere operation

Dual control drive corrector with 0.3x / 0.5x / 2x / 4x / 8x / 16x correction

NGC-microMAX Computer digital setting circles

• CCD autoguider compatible

AC and DC power (see below)

• Adjustable focal point

• Snap-fit Serrurier truss rods

• JMI's celebrated quality construction


Type:  Newtonian reflector
Mount:  Equatorial split-ring
Mirror:  12.5" f/4.5 Nova Optical Systems 2" thick Pyrex diffraction-limited enhanced primary (96% reflectivity), 2.6" diagonal enhanced secondary
Power:  12vDC operation with included AC and DC adapters (see below)
Weight:  approximately 120 lb., the heaviest single component is 40 lb.
Height:  64" assembled, 31" collapsed, Eyepiece height 59" at Zenith
Width:  26"
Depth:  29"
Finder:  9x50 straight through

Standard Equipment

Rotating Nose Assembly for comfortable viewing of any part of the sky.
EV-2n Focuser. (upgrades available)
Extension Tube for 2" Focuser.
25mm 1.25" Plössl Eyepiece.
9x50 Finder Scope
(straight-through) with dovetail mount.
Piggy-Back Camera Mount for piggy-back photography.
Off-Axis Counterweight for attaching to the piggy-back camera mount (2).
Serrurier Truss Rods snap fit into heat treated, spring steel cavities.
Adjustable Focal Point including three different nose assembly mounting positions for visual and photographic work.
Sliding Counterweights positioned along the truss rods for fine tuning the balance (3).
Split-Ring Equatorial Drive with 26" drive ring.
3-Point Large-Cup Flotation Mirror Cell.
Primary Mirror Dust Cover.

Integrated Optical Encoders for use with a "MAX" computer.
NGC-microMAX Computer digital setting circles with a 245-object database. (upgrades available)
Drive Corrector with dual axis control, 0.3x / 0.5x / 2x / 4x / 8x / 16x correction, North/south hemisphere operation and CCD autoguider interface (see warning).
AC or DC Power with 110vAC/60Hz or 220vAC/50Hz (specify) wall transformer or 12vDC cigarette lighter adapter.
Built-In Lifting Handle permits easy transportation.
Latitude Adjustment with scale for fine adjustment of latitude setting.   Adjusts from 30º to 58º (optional latitude modifications are available—see Latitude Modification below).

Product Manual

See Document Number 62 in our Document Library

* Telescope prices are for the standard telescope configuration.  Upgrades and Options are at additional cost.  The listed price also does not include the crating charge ($225) and any shipping and handling charges.  Please call for a shipping quote.  A 10% DEPOSIT is required with all telescope orders (5% IS NON-REFUNDABLE).  Telescopes are custom-built based on the options selected by the customer and therefore require time to build.  The remaining amount due must be paid before the telescope is shipped.

The Telescope ships in a crate approximately 34" x 34" x 37".

12.5" NGT Optional Upgrades

EV-1nM Focuser Upgrade
Add a Motor, Dual Speed Knobs and a Dial Indicator


EV-1n Focuser Upgrade
Add Dual Speed Knobs and a Dial Indicator


EV-2nM Focuser Upgrade
Add a Motor



Upgrade the EV Focuser

This option upgrades the focuser from the EV-2 model without motor (EV-2n) to the EV-2 model with motor (EV-2nM) or the EV-1 model with or without the motor (EV-1nM or EV-1n).  The EV-1 includes Dual Speed Knobs and a Dial Positioning Indicator.

EV-1n focuser with motor, Part Number EV1NMupg
EV-1n focuser without motor, Part Number EV1Nupg
EV-2n focuser with motor, Part Number EV2NMupg


Next Generation Computer
Upgrade the NGC-microMAX to an NGC-superMAX Computer


Next Generation Computer
Upgrade the NGC-microMAX to an NGC-MAX Computer


Upgrade Next Generation Computer

Compare Next Generation Computers (NGC) in our Computer Comparison Chart.  These computers can be used as stand-alone computers or they can interface with a personal computer (PC).  Either way they will guide you in finding objects in the night sky.

NGC-superMAX upgrade, Part Number SUPMAXupg
NGC-MAX upgrade, Part Number NGCMAXupg

Software Guided Telescope
(SGT-MAX) Upgrade
(PC Version)
Serial Interface Cable for the NGC-MAX
(for either PC or Standalone Operation)


Software Guided Telescope
(SGT-MAX) Upgrade
(PC Version)
B-BOX Interface
(for PC Operation Only)



Convert to a Software Guided Telescope System (SGT-MAX Computer)

Create a real-time link with a PC using planetarium software (not included).

The interface can be accomplished with either the NGC-MAX (see above) and the Serial Interface Cable (left) or a BBOX (left), the Serial Interface Cable (included with BBOX) and software (not included, see below).

NGC-MAX Version, Either PC or Standalone Operation, Part Number CBLBBOX
B-BOX Version, PC Operation Only, Part Number SGTMAXupg

NOTE The B-BOX Serial Interface links the telescope with a PC running planetarium software.  It does not act as a stand-alone guiding computer.

The Serial Cable (CBLBBOX) will allow the NGC-MAX computer to be used as a Serial Interface by mimicking the B-BOX Interface.
The SGT-MAX system requires PC software such as TheSky from Software Bisque.  This is a sample screen image of TheSky.



Add a 4" F-stop Opening in the Mirror Dust Cover


Add an F-Stop to the Primary Mirror Dust Cover providing a 4" aperture.

At the time of purchase only.)


Latitude Modification
For Low or High Latitudes



Latitude Modification for low or high latitudes.

The normal latitude range of the NGT-12.5 (30º to 58º) can be adjusted with modifications to the base of the telescope.  These modifications are only available with a new telescope order.  The telescope cannot be upgraded after purchase.  Call for specific details.


12.5" NGT Optional Accessories

Light Baffle
Nose Extension



Light Baffle nose extension

Prevents stray light from entering into the focuser.


Telrad Finder



Telrad Finder


Telrad Finder Mounting Adapter


Telrad Finder Mounting Adapter


Extra Sliding Truss-Rod Counterweight


Extra Sliding Truss Rod Counterweight (each)


Truss-Rod Light Shroud
Light-Weight Black Fabric



Truss Rod Shroud

Blocks stray light and air currents and helps keep dust off of the mirrors.  Made of light-weight black fabric with securing snaps and elastic at both ends.


Extra Center Counterweight
Offset Heavy Equipment



Extra Center Counterweight

A 4.3 lb Counterweight that screws into the bottom center of the mirror tub and offsets the weight of a CCD camera or other heavy equipment.

Bottom View of Counterweight
Handlebar and Wheels
Move Fully-Assembled Telescope



Handlebar and Wheels

For easily moving the fully-assembled telescope over most surfaces.  Uses 8" solid rubber ball bearing wheels.

The NGT-12.5's Handlebar and Wheels option gives easy wheelbarrow-style transportation.  Harold Harris (Alamosa, Colorado) easily loads his new NGT-12.5 into his van.

The NGT-12.5 telescope.
This images shows two NGT-12.5 telescopes side by side, one assembled and the other collapsed for transporting or storage.
The NGT-12.5 is a smaller version of the original NGT-18.
The 12.5 can be further disassembled by removing the mirror cell assembly.
All drive motor gears have a certain amount of slop.  To eliminate gear slop, the NGT-12.5 uses a two motor drive system.  The purpose of the second motor is to hold tension on the gears.  Once in a while you will need to "rack" the second motor to reestablish the tension.  This is done by pressing the right directional key while holding the motor switch on.  This switch, which can be found on the bottom of the motor housing, stops the second motor, thus creating the tension.
The nose assembly is removed from the top ends of the truss rods by supporting it with the arm while removing the thumbscrews.
The nose assembly is installed in the same manner, by supporting it with the arm while attaching the top ends of the truss rods with thumbscrews.
The ball ends of the truss rods are easily removed by slightly pressing on the spring clips while forcing the rods down toward the center of the tub (see inset photo).   Placing a couple of fingers between a pair of rods allows for removal of both at the same time without scratching the paint.  Most of the work should be done by leveraging the rods inward against the back of the spring clips rather than prying the spring clips open.
When reassembling, the ball end of a truss rod is inserted into the matching spring clip by holding the opposing side of the tub with the knee (to keep it from rocking), slightly opening the spring clip, then pressing the rod straight into the clip by pushing down on the top end of the rod.
The ring and tub assembly can now be removed from the base.  First, unscrew the quick-release knob at the south bearing as shown.  Next, disconnect the declination encoder and drive motor cable.  Finally, lift the ring and tub assembly off the base.
After disassembly, the telescope can be easily transported piece by piece.   If the mirror cell is removed, the heaviest single component (the ring and tub assembly) is approximately 40 pounds.
"[I put] a hole in my deck.  The [NGT-12.5] telescope sits on a dedicated column separate from the deck.  When I am not using the telescope, the top half of the scope comes off and an enclosure with a coffee table top protects the scope.  You can see the enclosure off to the side of the telescope in the attached picture.  It works great."  (Customer Skip Gjersdal, 2013)

What is a Next Generation Telescope?

The Next Generation Telescope (NGT) is a uniquely designed equatorial Newtonian.  It features a low profile, split-ring equatorial drive, open Serrurier truss rod design, rotating nose assembly, compact size, JMI's celebrated quality construction and now a Go-To computer (NGT-18 Model).  The NGT is a revolutionary instrument that has won awards and acclaim throughout the world.  It is available in 12.5" (f/4.5) and 18" (f/4.2 or f/4.5) apertures.

What is an Ampere-Hour?

The Ampere (amp) is a unit of measure of electrical current (or flow).  Batteries are often measured in ampere-hours to show the total electrical current capacity.  For instance, a fully charged seven amp-hr battery will supply one amp of current at a particular voltage for approximately seven hours before it is fully discharged (1 amp x 7 hours = 7 amp-hr).  If, instead, the battery is drained continuously at seven amps, it will discharge in approximately one hour (7 amps x 1 hour = 7 amp-hr).  This formula is only approximate because of many factors that effect the battery including construction, temperature, speed of discharge and variations in voltage.

Customer Comments

"The scope works very well.  I had it out the other night and was using my Denk II binoviewers on the Moon and it tracked at the Lunar rate flawlessly for over two hours (using eyeball polar alignment as described in the manual)!"  (R. F. W.)

"On reassembling the [NGT-12.5] telescope I was once again amazed at how well it holds collimation."  (L. S.)

"Do I like your NGT?  Oh yeah, 11 years old and going strong.  On a night of good seeing with collimation tweaked to the max, it can blow your mind."  (J. M.)

"WOW -- I LIKE THE [NGT-12.5] SCOPE -- IT WORKS.  ...  Really a very well designed scope.  The rotating collar works better than I thought it would and the counterbalancing is a snap.  The height angles for the eyepiece are proper and of course the optics are right on.  The colors are remarkable.  I guess even in a MAK, the colors get lost.  This is great.  ...  Thank for making such a good product."  (R. H.)

"I want to let you know that we have enjoyed using the NGT-12.5 scope that we purchased from you several years ago.  The scope has proven to be extremely easy to wheel out and set up and operate outside the center.  It is truly a general purpose scope providing wide views of low power, but also standing up to high magnifications of 205 - 410x when seeing conditions support it.  This latter feature was unexpected when I selected the NGT-12.5 and is a testimony to the excellent optics that you have selected.  High magnification views of M13 are breathtaking.  The separation of components of the double-double puts many expensive refractors of smaller aperture to shame, and transits of Io are easy to spot even when you're not expecting them.  I've been meaning to share my overall satisfaction with the NGT-12.5 with you for some time, and this occasion provided the opportunity."  (J. M.)

The following comments were re-written from a very broken English:  "I have a JMI NGT-12.5 telescope which I purchased in August of 2001 in Japan.  The NGT-12.5 is the most wonderful telescope that I have ever used.  I have been accepted for publication in the Japanese monthly astronomical magazine 'Tenmon Guide' with my JMI NGT-12.5 and SBIG ST-8e....  (I'm sorry, I can't speak and write English.  I used a Japanese-English dictionary to write this email.)  I want to introduce the NGT-12.5 to more and more Astronomers in the World!!!!!"  (J. M.)

"The JMI NGT-12.5 is probably the best scope I have ever owned.  Its workmanship is a masterpiece and the optics are as good or better than the four scopes with Zambuto optics in them.  They are the equal of my 15" Obsession, 10" and 17.5" Discovery and 12.5" Portaball.  It tracks excellently and is the showcase of most of the star parties I attend.  You could not go wrong purchasing one of these fine telescopes."  (Craig Woodley)

" NGT-12.5 is still doing fantastic.  I've now torture tested it at -25 degrees C and had no problems (although I had to wear battery socks and mitts at that observing session)."  (W. F.)

"My initial reaction is, 'What a superb telescope!'" ... The construction of the scope is impressive.  I had seen the ads for this scope over the past couple of years and read a glowing set of comments in 'Star Ware' about the engineering.  Seeing it in person and now understanding the construction a little better, I am very impressed.  This should be the last telescope I will ever feel compelled to own.  What I like best is how compact it is — it goes straight out the door from the living room to the deck with none of the inconvenience I experience in setting up and tearing down the SC.   ...There is no question that the optics are superior to anything I have used before. ...I have absolutely no buyer's remorse on this purchase.  It is an excellent, exciting telescope and has renewed my passion for astronomy..."  (B. G. M.)

"I am loving my NGT-12.5 that I bought from JMI last fall.  What a wonderful scope!  Since receiving the scope last October I have nearly finished off the Messier objects and the RASC finest 110 NGCs with this scope and can't believe how good the scope stays in collimation (I must have set up and taken the scope down about 20 times without having to collimate)  ...  It sure is nice to know there is someone there that I can email for technical support who knows their stuff.  Too many places have too little support once they sell their item, and I'm glad JMI isn't one of them!"  (W. F.)

"I must tell you, this is a wonderfully designed telescope.  Assembly is quick and simple, and the largest section weighs less than my LX200 8".  Optically the 12.5 is unbelievable, with galaxies just floating in deep rich dark star fields. ... WOW!  I ... have checked and tested the [periodic error] which I found does not exist on the NGT-12.5.   ...several people in my area have shown [an] interest and ... looking through an eyepiece will turn their heads every time.  Great work!"  (J. D.)

"The NGT-12.5 arrived! have really been right with all you told me!  Excellent craftsmanship and quality wherever I look.  A perfect mirror, solid and strong material for the scope, everything fits snugly at the first try.  That's what I really call good work!  ...a big Thank You..."  (R. K.)

Frequently Asked Questions (FAQ)

Q. How long does it take to set up an NGT-12.5?
A. After a little practice, the NGT-12.5 can be routinely assembled in less than five minutes.
Q. Does the rotating nose assembly make collimation difficult or impossible?
A. Contrary to erroneous reports on the Internet—No.  Here are some comments from Tom Johnston who builds the NGT-12.5 telescope:

"Not only do I build the NGT-12.5 here at JMI but I also own one.  I use it primarily to monitor faint periodic comets (using an ST7) for the IAU.

"There is a very simple pro and con relationship with the rotating nose on the NGT.  This ability to place the eyepiece at a variety of comfortable positions in an enormous factor.  The ease of use really cannot be realized until you've spent a night observing with it.  In addition, the rotating nose allows you to place a heavy CCD camera in a more balanced and less stress producing position above the tube instead of hanging off the side.  I personally would not give up my rotating nose.

"Here is the flip side.  It is difficult to collimate IF you have never done it before because it requires that you find the best possible collimation position relative to the entire rotation of the nose.  After you've done it a few times, it's easy.

"Before the scope leaves JMI, a laser spot must stay within the small white circle placed at the center of the primary mirror, throughout the 360 degrees of rotation of the nose.  The spot may dance around a little bit inside the circle but it remains INSIDE.  Using a Cheshire eyepiece, we then adjust the primary slightly until it is as close as it can get for the entire rotation.  There may be a few places in the circle where the Cheshire indicator is not perfect...but it will be off only slightly.  It's something you do not easily see visually or in a CCD image...but people like to talk about it anyway.  The only problems I have heard of are when people try to collimate it like a normal (non-rotating) Newtonian."
Q. Does the NGT hold collimation?
A. We have found that this telescope stays in collimation much longer than the average Newtonian.  Most Newtonian reflectors need to be collimated every other time they are used.  A recent floor model NGT-12.5 remained collimated over a span of at least 15 sessions.   These sessions included two trips to major star parties (RTMC and Okie-Tex) and periodic comet observations and imaging in the mountains of both Colorado and Arizona.
Q. How do you polar align the telescope?
A. There is a latitude adjustment screw that runs down the center of the telescope base.  The screw is parallel to the polar axis and can be visually pointed at the celestial pole.  This process can get you to within one-half degree of polar alignment in only seconds and, of course, you can use the good old stardrift method (see Document no. 8 in our Document Library).
Q. Can the NGT be leveled?
A. All NGT equatorials have leveling screws and a bubble level located on the base.
Q. How does dew affect the telescope?
A. All components of this telescope are rust proof.  Water on the drive ring has no affect on the tracking.
Q. How accurate is the split-ring drive?
A. Split-ring drives have little or no periodic error.  In a random test of a polar aligned NGT-12.5, it held the Dumbbell Nebula in a 30 arc minute field of view for over an hour.  Autoguiding feedback data from an SBIG ST7 CCD camera has confirmed this precision.
Q. How does the wind affect the NGT?
A. All truss tube Newtonian telescopes that use a shroud are subject to windy conditions.  Sudden wind gusts are more of a problem than sustained winds when imaging with a CCD camera.  However, we believe that this telescope is not affected by wind any more than a standard German Equatorial Newtonian telescope.  Tom Johnston, Production Manager and NGT-12.5 assembler, routinely uses production scopes (as part of JMI's Quality Control process) for gathering CCD images of periodic comets.  He reports very good results in moderate wind.
Q. Can the telescope be controlled by an autoguider?
A. With the proper cables and relay box (if needed) any autoguider can control an NGT-12.5 or NGT-18 telescope.