Mach1GTO German Equatorial Mount
with GTOCP3 Control Box - no longer available

* * Refer to Newest Mach1GTO with GTOCP4 * *




Shown with optional Keypad.

The Mach1GTO German Equatorial Mount with the GTOCP3 Control Box is no longer available to purchase. Please refer to information regarding the newest version of the Mach1GTO featuring our GTOCP4 Control Box.

The information below is provided for present owners and those who are curious about its history.

Sky & Telescope Magazine published a test report in the December 2007 issue entitled "Staying on Track". Earlier that year, Dennis di Cicco, Sky & Telescope Senior Editor, had tested Televue's TV-NP127is refractor, Apogee's Alta U9000 CCD camera and the Mach1GTO together over a number of imaging sessions. Based on his experiences, Dennis wrote three different reviews. The December article focuses on the Mach1GTO (PDF is linked with permission).

"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." .......

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 for himself!

Why a Mach1GTO?

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.

There is much to admire in the Mach1GTO. It is beautifully machined, intelligently designed, precisely fabricated and assembled, and it has sophisticated electronics and servo drive controls. But the bottom line is performance and results. In February 2007, Roland posted results of a very cold imaging session to the the Yahoo ap-gto group. The mount performed beautifully, and the results posted here prove it.

Whether your Mach1GTO makes a permanent home in your observatory, explores your favorite observing sites or travels to the ends of the earth with you, it will allow you to optimize your observing sessions to the max. Ideal instruments include: Astro-Physics and similar fast refractors up to our 160 mm f7.5 StarFire EDF, 8-11" SCTs, 6-8" Maks or any scopes of a similar size.

As Roland Christen, founder of Astro-Physics, has stated many times: "The single most important item for the imager is the mount. Next comes the mount. Then comes the mount.... Get the picture?"


Portable Enough for Airline Travel
Transport this rigid observing platform to your dream destination. The entire mount will fit into a single rugged case that will roll easily through airports or to your car. If needed, the R.A. and Dec. axes split easily into two pieces to fit into a more compact case.

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.

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 to quickly zero in on the pole for most non-critical observing or to get close before tweaking in for imaging. 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. Optional polar alignment scopes, discussed below, are available for more critical alignment

Multiple Options for Controlling your Mount in the Field or Your Observatory
You have your choice of the GTO Keypad (included), which is a full-featured handheld computer, PC computers using a wide variety of software with or without our ASCOM driver, Mac computers or even your mobile smart device (like your iPhone or iPad). GTO control options are discussed in detail at this link.

Mechanical Features

Precise Mechanical Fabrication
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.

Although the Mach1GTO is very light for its size and load rating, it has been machined out of solid aluminum to withstand the high axial and thrust loads that a medium-sized telescope places on the mount under real-world observing conditions. The mount is solidly built and will withstand gusting winds without excessive shake or vibration. We used high-quality machine tool bearings, rated in excess of 400 lb. static and dynamic load, on the main axis shafts. Both worm wheels turn smoothly with no runout throughout their 360 degree range.

Dennis di Cicco had this to say about the Mach1GTO's performance:

"The mount’s tracking and Go To pointing are among the most accurate I’ve ever tested. At the end of each night I’d park the scope and turn off the power. Whether an hour, day, or week elapsed until I’d power up the mount again and “resume from park," it would have perfect sync with the sky — even to the point of “hiding" stars behind my finderscope’s crosshairs when I’d check the alignment by slewing to them in a bright twilight sky . . .

Such Go To pointing precision comes in handy when shooting photographic mosaics, making a sequence of deep exposures of the same field on multiple nights, or hunting difficult targets by eye."

Precision-Adjust Rotating Pier Base / Hi-Res Azimuth Adjuster
The Precision-Adjust Rotating Pier Base / Hi-Res Azimuth Adjuster offers the same smooth and precise rotation as experienced when using the precision-adjust rotating pier adapters with our larger mounts. Regardless of the mount's load, hi-res adjustments can be made in azimuth with no lockdown needed, which could shift your position.

The azimuth adjuster knobs are now at the rear of the R.A. axis, which provides easier access and nearly doubles the precision of their adjustments. An etched line on the adjuster housing corresponds with the ridges of the knobs to provide a measured adjustment of 0.7021 degrees (42 arcminutes) per rotation or 0.05 degrees (3 arcminutes) per ridge.

These features were introduced in June 2011. If you own a mount shipped in prior years, the base can be easily removed and upgraded with these features.

Clutches and Interchangeable Motor / Gear Boxes
Clutches allow manual operation if power is not available. The R.A. and Dec. Motor / Gear Boxes are interchangeable.

Easy to Adjust and Maintain
The design of the Mach1GTO is straightforward with modular construction and no complicated internal wiring. We provide information in the Technical Support section of our website pertaining to typical adjustment issues. All electronics including the GTOCP3 control box, motors, gearbox or cables can be removed for servicing. The R.A. and Dec. axes can be shipped separately, if needed.

Route your cables through the mount for tangle-free operation and peace of mind.
Both axes have 2 inch clearance holes down the center with no shafts protruding into the holes. Wires from CCD cameras and accessories can be inserted from the bottom of the RA axis to emerge from the top of the Dec axis. Channels have been machined to allow the cables to be routed under the mounting plates. There is no restriction of rotation with the wires inserted - one can rotate both axes more than 360 degrees without catching the wires on any parts. The mounts shipped starting in June 2011, have a larger cable channel at the top of the Dec. axis.

Use Accessories you May Already Own
If you already own our previous 400 or 600E German Equatorials or other Astro-Physics mounts, you will be pleased to learn that many of the same accessories can be used with the Mach1GTO. These include counterweights, mounting plates, polar alignment scope (PASILL4L or the prior PASILL4 or PASILL3 models are preferred), piers and tripods.

Fast and Precise Polar Alignment
Our In-house designed, CNC machined Right Angle Polar Alignment Scope (RAPAS) allows you to polar align the Mach1GTO in record time and with a precision that permits you to quickly begin imaging. Its revolutionary right-angle design will immediately win you over. No longer will you be kneeling on the ground, straining your neck to polar align. Instead you will comfortably look down into the scope. Polaris, a 2nd magnitude star, is the only one that you need to position on the circular grid pattern of the reticle, so it is possible to align in light polluted skies. No other stars are needed.

There are several ways to determine where Polaris should be positioned on the circular reticle grid. The Astro-Physics ASCOM V2 driver includes the Astro-Physics Polar Alignment Scope Utility that duplicates the grid and provides a continuously updated positioning of Polaris. Custom apps are available for your iPhone/iPad/iPod Touch and Android or Windows devices. Those of you who wish to do it the old-fashioned way can calculate Polaris' position in local sidereal time.

Note: All Mach1GTO mounts shipped beginning in 2014 (serial number M10670 and later) will have the adapter for the Right-Angle Polar Alignment Scope built in. Mounts shipped in prior years must purchase the Right-Angle Polar Alignment Scope Adapter for Mach1GTO (RAPM1) separately.

If you already own the earlier PASILL4L, PASILL4 or PASILL3 versions of the Losmandy Polar Alignment Scope and wish to use it on a Mach1GTO mount that already has the adapter for the Right-Angle Polar Alignment scope (1.79" thread diameter on the backplate), you will need to purchase the Losmandy Polar Alignment Scope Adapter for 1100GTO, 1600GTO and some Mach1GTO Mounts (Q16030).


Mechanical Specifications

Construction All CNC machined aluminum bar stock, stainless steel, brass; stainless steel fasteners
Finishing and Assembly Every part is hand-finished and inspected. All assembly is done by hand, by highly skilled mount assembly staff.
Worm wheel - R.A./Dec. 5.9" (150 mm), 225 tooth aluminum
Worm gear - R.A./Dec. Brass, 0.705" (17.9 mm) diameter
Axis shaft - R.A./Dec. 2.36" (60 mm) diameter
Shaft axis bearings - R.A./Dec. 3.1" (78 mm) diameter, 2 per axis
Latitude range 0 to 70 degrees with or without the polar scope attached, engraved scale
Azimuth adjustment Approximately 13 degrees (+/- 6.5 degrees from center)
Counterweight shaft 1.125" (29 mm) diameter x 14.5" (368 mm) long [13.625" (346.1 mm) useable length], incl. washer and safety knob.
Optional counterweight shaft (M1053-A) available: 1.875" (48 mm) diameter x 10.7" (272 mm) long; fits inside Dec. axis for transport.
Weight of mount Total: 32.1 lb. (14.6 kg)
R.A. axis/polar fork: 16.5 lb. (7.5 kg)
Dec. axis: 11.5 lb. (5.2 kg)
Counterweight shaft: 4.1 lb. (1.9 kg)
Capacity Approximately 65 lb. (30 kg) scope and accessories (not including counterweights), depending on length. Recommended for: Astro-Physics and similar fast refractors up to our 160 mm f7.5 Starfire EDF, 8-11" SCTs and 6-8" Maks.
These are only guidelines. Some telescopes are very long for their weight or heavy for their size and will require a larger mount. Remember also that imaging requirements are more rigid than visual observation.

Instrument mounting interface

Refer to list of suitable mounting plates below
Diameter of base 5.800" (147.32 mm) diameter

GTOCP3 Servo Drive System

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.

Gear Accuracy and PE Performance
The heart of this mount is a precision gearbox using custom high-quality fine-pitch gears, coupled to a highly accurate worm and worm wheel. These parts are manufactured and assembled at our facility and individually tested to meet or exceed our periodic error specification of 7 arc seconds (+/- 3.5 arc sec.) before introducing any periodic error correction. The PE is smoothly variant with extremely low ripple or moment to moment error. In contrast, mounts that use integral gearboxes have very small spur gears with tiny teeth and too few of them. This generally causes ripples in the tracking rate which are difficult to guide out.

Each mount is rigorously tested on our specialized periodic error tester. Only mounts that provide an accuracy of 7 arc seconds or better will pass this inspection. If the mount exhibits greater error, the substandard part is identified, replaced and the mount is retested.

Pre-loaded PEMPro Curve
As mentioned above, the spec of 7 arc seconds (+/- 3.5 arc sec.) is the maximum native mechanical error inherent in the mount's RA axis WITHOUT any software correction. In order to optimize performance even further, we use a special version of Ray Gralak's PEMPro (described below) developed specifically for our test equipment. We generate a unique PE curve for each mount that we program into each GTOCP3 Control Box. Simply use the Keypad or your Astro-Physics software (ASCOM V2 driver, PulseGuide or APCC) to turn the PE Correction "on" and you will see results significantly better than our published 7 arc second spec without additional PEMPro runs! However, you may use PEMPro to further refine your PE, if you chose to do so.

PEMPro (available from CCDWare) is a very powerful program that allows the user to characterize the periodic error to a high degree of accuracy and to reduce it dramatically for long unguided exposures. It is especially useful for this mount since the average worm rotation error is already quite low, and the short term ripple error is almost nonexistent. If you are a serious imager, you may wish to consider purchasing PEMPro, especially down the road as your worm gear runs in. Depending on usage, re-measuring error and re-loading periodic error correction from one to four times a year is a good practice, especially if you do some unguided images from time to time. Additional PEMPRo runs are not necessary for visual observers.

GTOCP3 Control Box
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 Mach1GTO uses the same GTOCP3 Control Box (with the exception of the completely black-anodized exterior), as its big brothers - the 1100GTO and 1600GTO mounts. In fact, the control boxes for all three mounts are interchangeable with one another in an emergency. Extensive information regarding the GTOCP3 can be found here.

GTO Keypad (optional purchase)
The Keypad is a self-contained computer that allows you to control all essential telescope functions and includes an extensive database of objects. 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. Click here for detailed information regarding features and functions of the Keypad.

GTO Servo Drive System Specifications

Electronic components Rated for industrial and automotive applications
Motors Zero-cogging Swiss DC servo motors, enclosed in machined, aluminum housing
Motor encoder 2000 tic quadrature yielding an effective resolution of 0.050 arcseconds per tic
Motor reduction gear train 57.6:1 gear reduction through a custom built set of large diameter, fine-toothed, precision, spur gears for vastly superior performance
Servo Motor Control Box

GTOCP3 Control Box; black-anodized to match the mount
Included: machined aluminum Control Box Adapter

Hand-held computer (optional) GTO Keypad to control all mount functions.Includes extensive databases and tour features in a simple, intuitive interface. Firmware updates via the internet
Power consumption ~ 0.3 to 0.5 amps at 13.8 volts - tracking
~ 1.0 to 2.2 amps at 13.8 volts - both motors slewing at 1200x
Power requirements Nominal 12 volt DC supply at minimum of 5 amps continuous
Periodic error

7 arc seconds peak-to-peak (+/- 3.5 arc seconds) or less in one worm cycle (6.4 minutes); native, prior to any error correction

Maximum slew speed 5 degrees / second

Flexible Control with Your Keypad, Computer or even your Mobile Smart Device!

As this chart shows, there are many options available for controlling your mount. Take a few minutes to link to descriptions of the varied software and devices that are available.

You will be able to further link to a full size view of this chart.


The Mach1GTO can be mounted on a wide variety of piers and tripods. 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. Please check here first to find the information that you need.

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! With the new Precision-Adjust Rotating Pier Base / Hi-Res Azimuth Adjuster Upgrade Kit and larger cable openings, the Mach1GTO is even better than ever!

Price and Delivery Information

The Mach1GTO is no longer available with the GTOCP3. Please refer to information regarding the current version of the Mach1GTO. .

Mach1GTO - What's Included?

Items that You will Need for your Mount

Additional Accessories to Consider

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This page was last modified: October 2, 2017

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