Mach1GTO German Equatorial Mount
with GTOCP3 Control Box

Observatory Performance in a Small Package!

Includes GTO Keypad and PulseGuide software CD





Read the Test Report from the December, 2007 Sky & Telescope Magazine!
"Staying on Track" by Dennis di Cicco
(PDF - linked with permission)

In 2007, Dennis di Cicco, Sky & Telescope Senior Editor, tested and reviewed Televue's TV-NP127is refractor, Apogee's Alta U9000 CCD camera and the Mach1GTO at the same time.

"The mount just faded into the background as I worked with the scope and camera. Each night I’d turn it on; press a few buttons to slew to a bright star (usually before sunset), confirming that the mount was still synced with the sky; and go about my observing. Night after night the Go To pointing, sidereal tracking, and autoguiding remained virtually flawless. The fact that the mount proved so unobtrusive as I busied myself otherwise is, in my opinion, one of its greatest qualities — especially since its setup had been so easy."

Dennis' summary quote from the end of the article stated:

"If you’re in the market for a quality, midsize German equatorial mount that’s highly suited to portable and permanent installations, you should definitely consider the Mach1 GTO. I can’t imagine anyone being disappointed with its performance. The nameplate says “Astro-Physics,” and after months of using it, I know it’s good."

As a final testament to the Mach1GTO, Dennis decided that he did NOT want to give up the mount that he had borrowed for testing, so he purchased it himself!

Why a Mach1GTO?

Design Goals:

This is the first, compact, light-weight mounting that was designed for utmost portability while maintaining extreme rigidity and excellent tracking accuracy. No shortcuts were taken to achieve these goals. From the highly-accurate fine-pitch gearbox to the precision-machine tool bearings, to the innovative worm wheel and clutch design, this mount represents a new approach to this vital part of the overall imaging train.

The advent of modern CCD cameras and telescopes with high-resolution optics has placed greater demands on the ability of mountings to do their part to achieve precision tracking and guiding. At the same time, the mounting should be easy to use with adjustments and setups that are straight-forward and accurate. We have done everything possible to eliminate the frustrations and limitations inherent in a lesser mounting and so put the fun back into the hobby of amateur astronomy.

Principal features of the Mach1GTO Equatorial Mount:


Portable Enough for Airline Travel
Transport this rigid observing platform to your dream destination. RA and Dec axes split easily into two pieces, allowing the entire mount to fit into a single rugged carry-on case that will roll easily through airports or to your car. Please note that airline carry-on requirements may change over time or vary from one airline to another. We suggest that you confirm all requirements and restrictions before traveling!

Sophisticated Enough for Remote Operation
The Mach1GTO was designed from the ground up to take full advantage of the latest electronics. The integral internal cable channel allows multiple electronic devices to be used without the usual tangled cable nightmare. The Mach1GTO uses the same servo control box, the GTOCP3, as its big brothers - the 900GTO and 1200GTO mounts. In fact, the control boxes for all three mounts are interchangeable with one another in an emergency. This cutting edge electronic marvel coupled with software like Ray Gralak's wonderful PulseGuide (included) and your PC make remote operation a pleasure.

Operate with 12V battery or Regulated Power Supply
You can take it to the darkest skies and power it with a commonly available 12V battery. In the observatory, we suggest a minimum 5 amp filtered, regulated power supply.

Clutches and interchangeable motor / gear boxes
Clutches allow manual operation if power is not available. If, heaven forbid, your RA motor fails, simply swap the declination motor / gear box and resume tracking in RA. This will be a much appreciated backup procedure when you are far from home on an extended vacation.

Image Past the Meridian
The mount will track and guide well past the meridian in either direction if the object is located such that the telescope will clear the pier. This allows the user to set up the mount for a long series of exposures without stopping in the middle to flip sides. One can start the telescope under the mount while pointing at an object in the eastern part of the sky and track it all the way deep into the western sky. This is very useful for long exposure H-alpha or in cases where a large number of individual exposures are needed for stacking.
Dennis di Cicco had this to say about the "powerful meridian delay feature" in his 2007 review:

". . . makes it easy to set up photographs that track across the meridian without interruption. It may sound like a small feature on paper, but I found it extremely useful in the field . . ."

Easy Alignment for Non-critical Observing
You can align the Mach1GTO using setup routines in the keypad, or with a polar alignment scope to quickly zero in on the pole for most non-critical observing or to get close before tweaking in for imaging. (Polar scope not included. We recommend either the PASILL4L or the prior PASILL4 or PASILL3 models since they can rotate in the axis) You can even align the mount during the day with our clever Daytime Polar Alignment Routine (outlined in the Keypad Manual) for solar observing, viewing the planets at twilight, or just getting a jump start on a long night.

External Computer not Needed
The Keypad is a handheld computer with all of the features, functions and databases you need to tour the universe night after night. The unique firmware allows you to precisely polar align your mount in the field, even in broad daylight! The vacuum-fluorescent display with a temperature range of -40 degrees F (and C, they are the same in this instance), allows hardy observers to use this mount on cold winter nights. You can't do that with a PC or PDA! As new firmware versions are released in the future, you can upgrade your keypad directly from the download section of our web site - free of charge!

Control with personal computer, if desired.
All functions of the servo drive can be commanded from a laptop or desktop computer using popular planetarium program or PulseGuide. Depending on the features of the program, you can position your telescope, center your image and control tracking rate, remote focusing, reticle brightness and park at the end of your observing session. Examples of currently available software:

Serial to USB connectivity has been simplified by the addition of Keyspan Serial-to-USB devices to our product line. Please review the products on this page to determine which one will work best for your set-up.

Write your own computer program.
The Astro-Physics GTO protocol for the GTOCP3 Control Box is freely available to those who would like to write their own computer program for controlling the mount.

Precise Mechanical Fabrication

Highly accurate mechanics
Using modern CNC machining techniques, we make all components to a high precision level, which results in a final package that is solid and accurate in all respects. The critical angles are accurately machined so that the mount is orthogonal to a very high degree. This results in pointing accuracies well below 1 arc minute for a properly aligned mount.

Worm gear accuracy
Critical worm gear accuracy is maintained by special machining techniques developed at Astro-Physics after extensive studies and actual field operation. Our worm accuracies are second to none and are guaranteed to be 7 arc seconds (+/- 3.5 arc sec.) or less peak-to-peak for the Mach1GTO before introducing any periodic error correction! The periodic error of each mount is verified and optimized during our extensive testing procedures as described above. With good alignment and PEM training with the Keypad or PEMPro software, it is quite practical now to achieve unguided CCD images with today's hi-resolution cameras coupled to a 4" to 10" telescope.

Mechanical Features

Prototype Mach1GTO shown with SBIG STL-11000XM camera and its power supply with a variety of cables

Specifications of Equatorial Head

Worm Wheels - both axes

5.9" (150mm), 225 tooth aluminum

Worm gears

Brass, 0.709" (18mm) diameter

R.A. and Dec. thrust surfaces

4.1" (104mm) diameter


3.1" (78mm) diameter - 2 per axis

Periodic Error Maximum

7 arc seconds peak to peak, (+/- 3.5 arc sec.) or less in one worm cycle (6.4 minutes)

Axis Shaft Diameters

2.36" (60mm)

Latitude range

0 to 70 degrees

Azimuth adjustment

25 degrees (+/- 12.5 deg. from center)

Motor Power Consumption

400 mA - tracking
2 Amps - both motors slewing

Power Requirements

12V DC, 5 Amp. (Acceptable Range: 11.5 to 16V)


Approximately 45 lbs. (20kg) scope and accessories (not including counterweights), depending on length. Will accommodate Astro-Physics and similar fast refractors up to our 160mm f7.5 StarFire EDF, 8" - 11" SCT's and 6" - 8" Maks.
These are only guidelines. Some telescopes are long for their weight or very heavy for their size and will require a larger mount. Remember also that imaging requirements are more rigid than visual observation.

Weight of equatorial head

28.5 lbs (13.0kg); Declination axis is 11.5 lbs. (5.2kg); Right Ascension axis is 16 lbs.(7.3kg); Pier adapter is 1 lb. (0.5kg)

Counterweight Shaft 1.125" diameter X 14.5" long, 4.1 lbs. (29mm X 368mm, 1.9kg) This shaft uses the same 6 lb. and 9 lb. counterweights that were used with the 400, 600 and 800 series mounts.

Optional Counterweight Shaft (M1053-A) (must be purchased separately)

1.875" diameter X 10.70 " long, 7.7 lbs. (48mm X 273mm, 3.5kg) This shaft is the same diameter as the shaft for the 900 and 1200 mounts and uses the same counterweights as well as a 5 lb. counterweight produced especially for the Mach1GTO. Longer sizes and an extension are available. Requires Safety Stop (M12676).

Servo Motor Drive

The drive system uses a high-quality Swiss DC servo motor controlled by a microprocessor to an accuracy of 0.05 arc-seconds per step. Tracking is very smooth, noticeably smoother than any stepper motor drive or inexpensive servo motor. The system can be accurately controlled over a speed range of 4800:1, which allows 0.25x sidereal for manual guiding to 1200x sidereal for 5 degree per second slewing. The circuit draws only 0.4 amps when tracking the stars, 2 amps with both motors slewing and requires only 12 volts to operate. The servo drive will satisfy the requirements of the sophisticated, advanced astrophotographer, yet is easy for the casual, visual observer to use.

The GTOCP3 Control Box contains all of the circuitry to drive the two servo motors and the logic required to navigate the sky. It can be easily removed from the mount, if required.

The GTO Keypad is a self-contained computer that serves as the communication center for the operation of your GTO mount. We have designed the interface and firmware to be as intuitive and easy to use as possible while filling it with terrific features to make your observing session productive and pleasurable.

All of the Mach1GTO's electronics are now lead free. Astro-Physics believes that we who love the night sky should also love and protect our good earth. Please refer to GTOCP3 Control Box and Keypad for Servo Drive for additional information.

PulseGuide™ Software

Please note: Ray Gralak, the author of PulseGuide, is currently working on a new piece of software that will combine the Astro-Physics ASCOM driver, all the features of PulseGuide, plus additional features. The new software will also act as a hub for a number of other applications that can then all communicate with the mount through a single COM port. The new software will have a new name befitting its vastly increased capabilities, and will replace PulseGuide when it becomes available. In the mean time, here's the lowdown on the existing PulseGuide software:

PulseGuide is a stand-alone Windows (98, ME, 2000, NT4, XP, Vista and Windows 7) utility that provides complete remote control of the Astro-Physics Mach1GTO, 400GTO, 600EGTO, 900GTO, 1200GTO and 3600GTO mounts. It derives its name from its most distinctive feature, pulse guiding, which can improve unguided tracking. Specifically, it can help correct tracking errors caused by polar misalignment and atmospheric refraction. You can also train PulseGuide to track objects moving relative to the stars, such as asteroids, comets, and the moon. In addition to pulse guiding, PulseGuide also has many useful utility features. With just a few exceptions, it supports the entire serial Astro-Physics command protocol allowing full control of your mount through your PC. This program is indispensable for remote control of your mount. More information on our website ....

PulseGuide was written by Ray Gralak of Sirius-Imaging. Please refer to his web site for further developments and enhancements. The software will be provided on a CD-ROM with your Mach1GTO mount. Previous owners of any Astro-Physics mounts can download the software free-of-charge, courtesy of Ray. Many, many thanks to Ray for this powerful program.

Pier / Tripod Mounting Options

The Mach1GTO can be mounted directly into the top of an Astro-Physics 6" Portable Pier or on our 6" Eagle Adjustable Folding Pier (EAGLE6). It can also be mounted on the Adjustable Wood Tripod (AWT000) or the Lightweight Adjustable Aluminum Tripod (SDS400).The ADATRI adapter allows the Mach1GTO to be mounted on your own custom pier or tripod and can be purchased separately. To determine the appropriate pier height for your system, please try this Excel spreadsheet Latitude Dimension Calculator.


All Astro-Physics mounts are supported by a dedicated staff who will assist with any issues that may arise. You can talk to a real person in a timely manner. Astro-Physics staff also participate the ap-gto user groups in the Yahoogroups forum. The user group is comprised of GTO owners who are willing to share their wealth of experience using their mounts as well as imaging strategies and other concerns of advanced amateurs.

We have prepared some pertinent support documents relating to this mount and many of our other products on our Technical Support page. You may find the information that you need simply by clicking here.

The Mach1GTO is HOT!

In addition to Dennis di Cicco's fine review of the Mach1GTO, we were excited and honored to have the Mach1GTO chosen as one of Sky & Telescope's Hot Products for 2007!

Price and Delivery Information

With rare exception, the Mach1GTO is not available on the shelf for immediate purchase. We typically maintain notification lists so that we can notify prospective customers when the mount is available to order. Please refer to our availability page for more information on our notification lists. If you are not already on the notification list for the Mach1GTO, you can sign up on our online notification form. An automatic confirmation e-mail will be sent to you for your records. Refer to Notification Update periodically to find out the status of our mount and telescope production runs - what we are making throughout the year.

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This page was last modified: September 20, 2013

Astro-Physics, Inc.
11250 Forest Hills Road, Machesney Park, IL  61115, U.S.A.
Phone: 815-282-1513   Fax: 815-282-9847