Mach1GTO German Equatorial Mount (MACH1GTO)

Brand :

Discontinued: No Longer Available

Historical information and alternative recommendation::
Please refer to the description below.

The Mach1GTO is no longer available and was replaced by the Mach2GTO in 2020. 


The following historical information is provided for your reference. 

Why a Mach1GTO?

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 addition to Dennis di Cicco's excellent review of the Mach1GTO in Sky & Telescope magazine,  we were excited and honored to have the Mach1GTO chosen as one of Sky & Telescope's Hot Products for 2007! With the new GTOCP4, Auto-Adjusting Motor/Gearboxes, Precision-Adjust Rotating Pier Base / Hi-Res Azimuth Adjuster, rear-mounted azimuth adjusters and larger cable openings, the Mach1GTO is even better than ever!

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 Polar Alignment for Non-critical Observing

You can align the Mach1GTO using setup routines in the optional keypad to quickly zero in on the pole for most non-critical observing or to get close before tweaking in for imaging. Our optional Right-Angle Polar Alignment Scope will allow you to quickly zero in on the pole or the polar alignment routine in PEMPro (optional) will guide you through the process. 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.

Multiple Options for Controlling your Mount in the Field or Your Observatory

You have your choice of the GTO Keypad (optional), 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.

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, piers and tripods.

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.

Auto-Adjusting Motor/Gearboxes

Our motor/gearboxes were designed to be responsive for precision astro-photography, while at the same time making it super easy to use and adjust.

  • Spring-loaded worms maintain full contact under all guiding and slewing conditions
  • Automatic setting for worm mesh requires no adjustments over long time periods
  • Precision balance mechanism allows full backing off the worm from the worm wheel
  • Very low backlash geartrain eliminates Dec reversal delays and provides high position accuracy during guiding

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 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 allow manual operation if power is not available and rebalances of your telescope without disturbing the motor box..

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 GTOCP4 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 than the earlier mounts..

Fast and Precise Polar Alignment

Our clever 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.

In the northern hemisphere, 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. Southern hemisphere observers will use the grid for Sig Octans.

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).


Gear Accuracy and PE Performance

The GTOCP4 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 and repeatable from one worm cycle to the next, which enables PE correction to be very accurate. The system can be precisely 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 approximately 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 astro-imager, yet is easy for the casual, visual observer to use.

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 commercial 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 developed specifically for our test equipment. We generate a unique PE curve for each mount that we program into each GTOCP4 Control Box. Simply use the optional 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.

GTOCP4 Control Box

The GTOCP4 Control Box offers multiple connection options to suit your requirements including wifi, ethernet, USB and serial ports. In addition to all the features carried forward from previous control boxes, the GTOCP4 applies safety slew logic to all slew commands. Future firmware updates will be available via direct downloads.

The GTOCP4 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 1100GTO uses the same GTOCP4 Control Box as 1600GTO and Mach1GTO. In fact, the control boxes for all three mounts are interchangeable with one another in an emergency. However, the absolute encoder function is only available in the control boxes sold with those mounts.

Be sure to review extensive information regarding the GTOCP4.

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. Many people do not want to bother with a computer in the field and like the handiness of the Keypad and its ability to operate in very cold temperatures. The Keypad is an ideal choice for these users.

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.

Optimized for Astronomy

Astro-Physics mounts and the Astro-Physics GTO Servo Control System are designed from the outset as tools for celestial observing and imaging.  These mounts do not have any military or defense applications. Applications like missile, airplane, or very low earth orbit satellite tracking require faster tracking rates and more rapid changes to those tracking rates than our mounts allow.   Note that the ISS is generally within the mount’s tracking rate capabilities. 

Dimension Calculator

To determine the appropriate pier height for your system and to calculate many of the dimensions that vary with your latitude setting, please try this Excel spreadsheet Latitude Dimension Calculator.

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. 0.705" (17.9 mm) diameter, special low-wear alloy
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 13.625" (346.1 mm) useable length, incl. washer and safety knob. Weight 4.1 lb. (1.9 kg)

Optional counterweight shaft (M1053-A) available: 1.875" (48 mm) diameter x 9.675" (246 mm) useable length; fits inside Dec. axis for transport. Requires Safety Stop.
Weight of mount Total: 28 lb. (12.7 kg)
R.A. axis/polar fork: 16.5 lb. (7.5 kg)
Dec. axis: 11.5 lb. (5.2 kg)
Capacity Approximately 65 lb. (30 kg) of scope and accessories, depending on length. Recommended for: Astro-Physics and similar fast refractors up to our 160 mm f7.5 Starfire EDF, 8-12" SCTs and 8-10" 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
Diameter of base 5.800" (147.32 mm) diameter


GTO Servo Drive 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 GTOCP4 Control Box, removable
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 0.6 amps at 13.8 volts - tracking
~ 1.3 to 2.5 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

+/- 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 link to a full-sized view of this chart.


PEMPro Software, Version 3

PEMPro (Periodic Error Management Professional), Version 3, by Sirius Imaging is included with this mount. It is a very powerful Windows software application that allows you to correct your mount's periodic error, polar alignment and backlash using your CCD Camera or Webcam to dramatically improve tracking and guiding. As mentioned previously, our extensive testing procedures include several PEMPro runs so that your new mount will perform with optimum PE correction out of the box. Simply use the Keypad, the ASCOM driver or APCC software to turn PE Correction "on." Although you will not need to use PEMPro when you receive your mount, you may wish to do a PEMPro run at a later date after the worm gear has run 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. PEMPro also includes a powerful polar alignment routine.

Mach1GTO German Equatorial Mount

  • Mach1GTO Equatorial Head (R.A. & Dec. Assembly) with Servo Drive Motors (includes built-in adapter for Right-Angle Polar Alignment Scope)
  • GTO Servo Control Box (GTOCP4)
  • Control Box Adapter (CBAPT)
  • 13.675" Stainless Steel Counterweight Shaft, 1.125" diameter (M8084-A) with Machined Safety Stop Knob (MSSKB)
  • Y-Cable for R.A. and Dec. (SM1GYCR)
  • Power Cable Set for GTOCP4, includes 6' Cable with PowerPole Connector, 18" Cable with Cigarette Lighter Plug and 18" Cable with Ring Terminals (CABPP4SET)
  • 15' Straight-through Serial Cable (CABSER15)
  • 1/4-20 Machined Knob Kit (M1485KBKIT)
  • Allenhead wrench set
  • CD containing: PDF of Mach1GTO and Keypad instruction manuals
  • Manual: Mach1GTO German Equatorial
  • Registration Card
  • ASCOM driver, available by download

Items that You will Need for your Mount

  • Mounting Plates: FP1500, 900RP, DOVE15, DOVEDV10 and DOVELM162
  • Pier or Tripod: Astro-Physics Portable Pier - 6" diameter, heights 24" 54"; Astro-Physics "Eagle Adjustable Folding Pier (EAGLE6); or Berlebach Planet Tripod (AWTBER2). If you choose the Berlebach tripod, be sure to include the Control Box Extension Adapter (Q6280KIT)
  • 12V Battery or Power Supply that convert 110VAC to suitable DC: 13.8 volt, 5 amp Regulated Power Supply with Cigarette Lighter Receptacle (PS138V5A)
  • Counterweights: Stainless Steel Counterweights - 6, 9 and 14 lb.

Additional Accessories to Consider

  • GTO Keypad with 15' Coiled Cable and Keypad Protector (KEYVFK)
  • Astro-Physics Command Center (APCC) software
    Right-Angle Polar Alignment Scope with Illuminator (RAPAS)
  • Polar Alignment Scope (PASILL4)
  • Pier Accessory Trays and Support Bar
  • Alternate Counterweight Shaft: 9.675" x 1.875" diameter Stainless Steel Counterweight Shaft (M1053-A) and Safety Stop (M12676) (requires alternate Counterweights - 5, 10, 18 lb.)
  • Alternate Counterweights: Stainless Steel Counterweights - 5, 10, 18 lb. (require alternate Counterweight Shaft - M1053-A and Safety Stop - M12676)
  • 24" Servo Extension Cable for mounting GTOCP4 in lower positions (CABGTO24) on 6" Eagle or other pier
  • PEMPro Periodic Error Management Software from CCDWare
    Tripod Adapter (ADATRI) - attach to tripod or other flat surface
  • Mount Adapter: to attach Losmandy HD Tripod or Losmandy MA Meade Field Tripod Adapter to Astro-Physics 400/600/900/Mach1 Mounts (LT2APM)

Northeast Astronomy Forum (NEAF) 2016

During the 2016 Northeast Astronomy Forum (NEAF),Roland Christen of Astro-Physics demonstrated some of the functions of the Auto-Adjusting Motor/Gearboxes, the Absolute Encoders and GTOCP4 Control Box (begins at 4:14). Although the 1600GTO mount is shown, these same features are available for the Mach1GTO. Dennis DiCicco, editor of Sky & Telescope magazine,opens the interview with a discussion of the 17" f8 Flat Field Astrograph.

Northeast Astronomy Forum (NEAF) 2013

The 1100GTO was introduced at the Northeast Astronomy Forum (NEAF) in Suffern, NY in April 2013. In the video below, George Whitney, from the Astro-Physics Technical Support staff, explains key features of the 1100GTO in an interview conducted by Dennis DiCicco, Sky & Telescope editor. We also invite you to view the entire video for demonstrations of these additional exciting products: 1600GTO German Equatorial mounts with discussion of the Absolute Encoder System used in both the 1100GTO and 1600GTO mounts, Right-Angle Polar Alignment Scope, the 10 x 60 Vario Finder with Quick Release Guider Bracket and the Astro-Physics Command Center (APCC) software.


s-t-thumb.jpgSky & Telescope Magazine published a test report of the Mach1GTO with the GTOCP3 Control Box (prior version) 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." .......

"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."

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."

Since the review, we have added newer features. The Mach1GTO is even better than ever: GTOCP4 Control Box, Precision-Adjust Rotating Pier Base / Hi-Res Azimuth Adjuster, built-in adapter for the Right-Angle Polar Alignment scope, rear-mounted Azimuth Adjuster and larger cable openings and now the GTOCP4 Control Box and Auto-Adjusting Motor/Gearboxes.