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Stargazing July 13th ✦ 7pm-10pm
Stargazing July 13th ✦ 7pm-10pm

Mach2GTO German Equatorial Mount


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We are thrilled to offer our Mach2GTO Universal Robotic mount that sets a new standard for portable telescope mounts. It is so easy to use that you will be up and running in no time at all and the mount will simply disappear into the background. No fuss, no bother.

Universal Robotic means that Mach2 fulfills all of the requirements of a robotic mount for automated operation for imaging, satellite tracking, comet tracking, star survey work and others. In addition, the clutches allow it to be used manually for star sweeping. It is so easy to use that it can be set up quickly in the field with minimal effort and no complicated startup routines. The encoders keep track of the axis positions at all times whether parked, unparked, power on or power off.


  • Polar Align, Power Up and Go!
  • Renishaw Absolute Encoder for the ultimate in precise tracking - no SDE or random errors above 1/4 arc sec. Extended Temperature option available. 
  • Absolute encoder provides near zero tracking error and resists outside influences such as wind and cable drag
  • Precision balancing via the clutches without taking the worm gears out of mesh
  • Brushless Micro-step Servo System for precise and whisper-quiet slewing and tracking

  • Dual-model pointing and tracking rate correction even with the telescope in the counterweight UP position. using Astro-Physics Command Center (APCC) Pro version, included
  • Custom tracking rates in both axes (for asteroids, comets, satellites)
  • Auto-Adjusting gear mesh
  • Image all night without meridian flip, as long as your scope clears
  • Daytime polar alignment is now simplified since we have encoders to set the positions
  • Precision azimuth adjuster with rotating base
  • Built-in bubble level
  • Right-angle polar alignment scope (optional) 
  • Internal USB 3.0 cable
  • Fully supported enhanced ASCOM driver 
  • Threaded for QHY Polemaster AP900 adapter (shown in photo)
  • Portable – 42 lbs
  • Operate with 12V battery or up to 24V power supply
  • Ideal for 6-7” refractors, 8-12” SCTs and Maks
GTO Servo Drive System

GTOCP5 Control System

Our GTOCP5 control system combines the precision performance of the Renishaw Resolute Absolute Encoder with the whisper-quiet motion of brushless micro-step servo motors to produce a very accurate observatory-grade mount that can also be set up in just a few minutes in the field. The mount can be operated manually via the clutches or electronically with the encoder loop providing the pointing and tracking functions.

  • Use of Absolute Encoders means that the mount always knows where the axes are pointing and doesn't need to establish home on power-up.
  • The mount can be operated manually via the clutches or in full GoTo mode via keypad or external software.
  • Absolute Encoders are extremely accurate in slewing, pointing, tracking, guiding. Periodic error and backlash, reversal delays in Dec are eliminated.
  • Rapid feed-forward servo loop stiffens the axes against outside disturbances such as cable drag and wind loading.

  • Both axes can be run at custom tracking rates from sub-arc second motions per hour to 1000x sidereal.
  • The GTOCP5 brushless servo system can be run from 12 volts to 24 volts with max slewing from 1200X (5 deg/sec) to 1800X (7.5 deg/sec).
  • The power to the motors is self-limiting and cannot cause any kind of damage to the windings or the electronics, even when in a stalled state.

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. The new V5 version includes modeling routines for pointing, tracking and orthogonality.  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. 

Absolute Encoders

Mach2GTO and Renishaw Absolute Encoders

Mach2 Tracking Performance with Absolute Encoders - PE = 0.21 arc seconds


All of our 1100GTO and 1600GTO mounts with Absolute Encoders installed have always used the Renishaw Resolute Absolute Encoders for precise positioning and tracking. Now our newest mount, the Mach2 has the Renishaw Resolute encoder built into every mount. What are the main differences between the Renishaw and other less expensive relative encoders?

Lab Certified Accuracy! 
The Renishaw encoder accuracy is verified against a laboratory standard. Each ring comes certified with its own calibration measurement. The maximum guaranteed error on these rings translates to less than 1/2 arc second per hour tracking error.

Highest Resolution for Unparalleled Tracking Accuracy!
The Renishaw Resolute read-head interpolates a special barcode that is engraved on the matching stainless steel ring into 67 million individual addresses. Every address is unique and fully reproducible down to sub-arc second levels. This is not possible with any relative encoder system.

Ripple and Resonances – NOT with Astro-Physics!! 
Relative encoders use a simple ring that has engraved marks with separations on the order of 60 to 100 arc seconds between ticks. In order to achieve sub-arc second resolution, the gaps between these marks are filled in electronically by a method known as interpolation. Even the best interpolation methods have errors on the order of 5% (3 to 5 arc seconds). When used in a telescope drive system these relative encoders introduce a fast moving ripple in the RA tracking rate of 3 to 5 arc seconds, although the average or RMS value of this error can be quite low.

These peak excursions cause stars to move slightly back and forth in the RA direction during sidereal tracking. This tracking ripple can remain hidden when imaging with short wide-field scopes, but will manifest itself when using long focus instruments for high resolution work. It is generally a fast moving error, so it cannot be guided out.

No Sub-divisional Error! 
Because of the ever present interpolation error (SDE) with low-cost relative encoders, we decided long ago that we would not use them for tracking. Renishaw absolute encoders use a different type of interpolation system that smooths out the SDE to a level that is not detectable. There is no mechanism for a relative encoder to remove the SDE.

Never Needs Homing. Simply Polar Align; Power Up; and GO!! 
An absolute encoder never needs to be homed. It is always home the minute power is applied. It always knows where it is and transmits the exact shaft position to the control box at all times.

Dependability to Astro-Physics Standards!
We have used Renishaw encoders for many years on our larger mounts, both in portable setups and in observatory remote installations. They have been totally reliable. Renishaw encoders are also considered to be the gold standard in the machine tool and robotics industries where precision is required. Yes, they are much more expensive than a simple relative encoder, but for the type of accuracy required in a telescope mount, there is nothing out there that comes close. We know, we have been evaluating options for years.

Benefits of Absolute Encoders

The utility of absolute encoders varies from one mount brand to another.  Some manufacturers make very limited use of encoders and use relative (not absolute) encoders to provide a potential benefit to tracking and nothing else.  In regards to the Mach2GTO, the benefits are:

  • The mount always knows where it is pointed regardless of power loss, movement of the axes when the power is off, bumping the mount or wind movement. 
  • No rehoming is required for remote locations should there be a power loss.
  • Periodic error is fully corrected. No need for occasional PE measurement curves.
  • Zero backlash in both axes for precision guiding.
  • Dual-axis absolute encoders allow for variable tracking that automatically adjusts for refraction parameters.
  • Very accurate pointing makes it easy to find very faint objects.
  • Very precise tracking such that unguided imaging may be accomplished with an appropriate optical/imaging setup.
  • Very precise guiding, if needed, with instant response in both axes.  Guiding is only needed to correct for optical/imaging train issues, not mount issues.
  • Corrects for polar misalignment and repeatable mechanical flexure.
  • Very precise dual-axis tracking is very important for high precision tracking on objects like comets, asteroids, artificial satellites, where the mounts use a "self-guiding" function based on orbital elements.

We invite you to review the additional technical information regarding the encoders to find out what they can do for you.  


Mechanical Specifications

Construction All parts CNC machined aluminum, stainless steel, brass bar stock; 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. 0.71" (17.9 mm) diameter, brass
Axis shaft - R.A./Dec. 1.77" (45 mm) diameter
Latitude range 0 to 68 degrees, engraved scale
Azimuth adjustment Approximately 13 degrees (+/- 6.5 degrees from center)
Diameter of base 5.80" (147.32 mm) diameter
Weight of mount Total: 42 lb. (19.8 kg)
Counterweight shaft 1.875” (47.6 mm) diameter x 13.625" (346 mm) usable length, incl. washer and safety knob. Weight 10.9 lb. (4.9 kg). For light-weight scopes you may not need any counterweights!
Capacity Approximately 75 lb. (34 kg) scope and accessories only (maximum capacity depends on scope diameter). Refer to the graphic that discusses weight capacity calculation.


GTO Drive Specifications

Electronic components Rated for industrial and automotive applications
Motors Brushless micro-step servo system, enclosed in machined aluminum housing
Absolute Encoders R.A. and Declination axes
Periodic error (native) 0.25” arc seconds peak-to-peak, 0.05 RMS
Servo Motor Control Box GTOCP5 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 requirements

Nominal 12 to 24 Volt DC supply, minimum of 5 amps continuous
12 Volts: Tracking - 1.5 amps DC,  Slewing, max rate 1200x, 4.2 amps (50 watts), both axes slewing
24 Volts: Tracking - 0.8 amps DC,  Slewing, max rate 1800x, 3.6 amps (86 watts), both axes slewing

Maximum slew speed

5 degrees / second at 12V
7.5 degrees / second at 24V


Control Options

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.


What's Included

Mach2GTO German Equatorial Mount

  • Mach2GTO Equatorial Head with Dual Absolute Encoders 
  • GTO Servo Control Box (GTOCP5)
  • Control Box Adapter (CBAPT)
  • 13.675" Stainless Steel Counterweight Shaft, 1.875" (47.6 mm) diameter with Machined Safety Stop Knob (M12676)
  • 6' Cable with PowerPole Connector (CABPP6) and Clip
  • 1/4-20 Machined Knob Kit (M1485KBKIT)
  • Allenhead wrench set
  • AC-DC Power Supply, universal 85-240V to 24V DC at 10 amps
  • ASCOM driver, available by download
  • APCC Software, Pro version (APCC-PRO)
  • Thumb Drive containing: PDFs of manuals and other handy utilities.
  • Manuals: Mach2GTO German Equatorial and GTOCP5
  • Registration Card

Items You will Need for Your Mount

  • Counterweights: Stainless Steel Counterweights - 5, 10, 18 lb.  (5SCWT, 10SCWT, 18SCWT, 30SCWT188) (due to larger diameter 30SCWT188 cannot be used at top of the shaft)
  • Mounting Plates: DOVEDV10 or DOVELM162
  • Pier or Tripod:
    • Astro-Physics Eagle Adjustable Folding Pier (EAGLE6-EZ)
    • Berlebach Planet Tripod (AWTBER2).  You will also need the Control Box Extension Adapter (Q6280KIT)
    • Flat Surface Tripod Adapter (ADATRI) if you wish to attach to a flat surface
    • Astro-Physics Portable Pier - 6" diameter, height: 24"
  • Refer to USB 3.0 Internal Cable Considerations below to plan your cable requirements.

Additional Accessories to Consider

  • GTO Keypad with 15' Coiled Cable and Keypad Protector (KEYVFK2)
  • Right-Angle Polar Alignment Scope with Illuminator (RAPAS), requires Bracket listed below
  • Bracket to Attach Right-Angle Polar Alignment Scope Adapter to Mach2GTO Mounts (RAPM2
  • Pier Accessory Trays (TRAY06 and TRAY06H) and Support Bars (TRAYSB1 and TRAYSB)
  • Side-by-Side Dovetail Plates for D-Style Dovetail Saddles (SBD13SS, SBD18SS)
  • 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/Mach2 Mounts (LT2APM)
  • 10.7" x 1.875" Counterweight shaft (M1053-A) to use with very small scopes. 
  • 16.975" x 1.875" Counterweight Shaft (M9404-B) for heavier loads rather than adding a shaft extension. 
  • 14.5" x 1.125" Counterweight Shaft (M8084-B) - use with corresponding counterweights that you may already own
  • Alligator Clips with APC Fuse to PowerPole Connector (CABPPAL)
  • Powerwerx In-line Watt Meter shows volts, amps, watts, amp-hours, watt-hours. (CABPPWM)

USB 3.0 Internal Cable Considerations

As mentioned, the mount includes an internal USB 3.0 cable for your convenience. It is important to remember that passive USB 3.0 cables (including the 2 foot internal cable) can be no more than 9 feet (3 meters) in length from a powered port and passive USB 2.0 cables can be no more than 15 feet (5 meters) in length from a powered port. With that in mind, you will need to plan your computer cabling carefully. With USB, shorter is better.  These are our current recommendations:

Connecting Computer to Mount Internal Input
These connections are made to the Mach2GTO Back Plate on the RA axis.

Using USB 3.0 Active Cable and Short USB Cable

  • USB 3.0 Active Cable (male A-to-female A).  Example: Tripp Lite USB 3.0 Active Extension Repeater Cable (USB-A M/F) 
  • USB 3.0 male A-to-male A Cable for Data Transfer (short cable).  Example: UGREEN USB 3.0 Type A Male-to-Type A Male Cable for Data Transfer, 1.5-ft

Connecting Mount Internal Output to Communication/Power Hubs
These connections are made to the Dec axis Top Plate just under your mounting plate.

Using Pegasus Astro “Ultimate Powerbox V2” and “Pocket Powerbox Advance”

  • USB 3.0 male A-to-male B Cable (standard)
  • Custom 12 volt Cables with Anderson Powerpole Connector to XT-60 Female Connector (Ultimate Powerbox) or RCA Male Connector (Powerbox Advance).  It is recommended to use a 16 to 18 AWG cable. 

Using USB 3.0 Communication Hub and RIGRunner Power Distribution

  • USB 3.0 male A-to-male B Cable (standard)
  • USB 3.0 Powered Hub.  Example: Gearmo USB 3.0 4-Port Industrial Metal Hub w/15KV ESD Protection
  • Powerwerx Power Distribution
    • Custom 12 volt Cables with Anderson Powerpole Connectors
    • 4 Position Power Distribution Block for 15/30/45A Powerpole Connectors
    • West Mountain Radio RIGrunner 4005

Using Primaluce Lab Eagle3 Communication Hub and Power Distribution

  • USB 3.0 male A-to-male B Cable (standard)
  • Primaluce 12 volt Power Cable to Anderson Powerpole Connector

Mach2GTO German Equatorial

GTOCP5 Control Box


The Mach2GTO is in production. Please complete the Mach2GTO Notification Request Form if you would like to be notified when a mount is available for you to order.