Astro-Physics Mach2GTO Computerized German Equatorial Mount

Brand: Astro-Physics


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  • For time frames or questions, please contact us at 800-483-6287.
  • The Renishaw Absolute Encoder brings ultimate precision tracking with no SDE or random errors above 1/4 arcsec
  • High-end electronics and sturdy structural design make the Mach2GTO almost wholly immune to outside influence such as extreme winds and heavy cable drag.
  • Easy, precise balancing via clutches. No need to work with the worm gears!
  • Smooth and whisper-quiet slewing and tracking to brings this mount a few steps closer to perfection.
  • Current listed prices include shipping costs to contiguous states. AK, HI, and international shipping will still require a shipping cost.

Product Details

  • The Astro-Physics Mach2GTO Computerized German Equatorial Mount:

    About The Mach2GTO Universal Robotic Mount 

    This mount 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.

    Main Features of the Astro-Physics Mach2GTO EQ Mount

    • 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
    • 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
    • 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 & compass
    • Right-angle polar alignment scope (optional)
    • Through-mount cabling (optional)
    • Modeling in Keypad & GTOCP5
    • Fully supported enhanced ASCOM driver
    • Portable – under 40 lbs
    • Operate with 12V battery or up to 24V power supply
    • Ideal for 6-7” refractors, 8-12” SCTs and Maks

    Weight Capacity vs Torque

    GTOCP5 Servo Control System

    Astro-Physics developed a new control system which combines the precision performance of the Renishaw Absolute Encoders 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 don'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 dead 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 has modeling capability that is suited for quick setups in the field for portable operation. No computer needed.
    • 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.

    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.


    Mach2GTO and Absolute Encoders

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

    Mach2GTO Periodic Error

    All of our 1100GTO and 1600GTO mounts with Absolute Encoders have always used the Renishaw Resolute Absolute Encoders for precise positioning and tracking. Now our newest mount, the Mach2 has Renishaw encoders 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. 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.

    Comparing Renishaw Resolute Absolute Encoder with a Precision Relative Encoder

    Periodic Error Comparison

  • specifications

    DEC Worm Wheel150mm Diameter 225 Teeth
    Drive TypeBrushless micro~step servo system
    Encoder Resolution67 million individual addresses
    Encoder TypeAbsolute Encoders
    Head DesignEquatorial
    Instrument Capacity75 lb
    Latitude Range0 to 67 Degrees
    Mount Head Weight39lb
    PortsRS 232
    PortsUSB 2.0
    RA Worm Wheel150mm Diameter 225 Teeth
    Slew Speed7.5 degrees / second at 24V
    Tracking Accuracy±0.25 Arcseconds
  • included items

    Mach2GTO German Equatorial Mount

    • Mach2GTO Equatorial Head (R.A. & Dec. Assembly) with Brushless Micro-step Servo System
    • GTO Servo Control Box (GTOCP5)
    • Control Box Adapter (CBAPT)
    • 13.675-inch Stainless Steel Counterweight Shaft,1.875-inches (47.6 mm) diameter with Machined Safety Stop Knob (M12676)
    • Power Cable Set for GTOCP5, includes 6' Cable with PowerPole Connector, 18-inch Cable with Cigarette Lighter Plug and 18-inch Cable with Ring Terminals (CABPP4SET)
    • 15-foot Straight-through Serial Cable (CABSER15)
    • #1/4-20 Machined Knob Kit (M1485KBKIT)
    • Allen head wrench set
    • CD containing: PDF of Mach2GTO and Keypad instruction manuals
    • Manual: Mach2GTO German Equatorial
    • Registration Card
    • ASCOM driver, available by download

    Items You will Need for Your Mount

    • Mounting Plates: DOVEDV10 or DOVELM162
    • Pier or Tripod: Astro-Physics Portable Pier - 6-inch diameter, heights from 24 to 54-inches; 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 converts 110V AC to suitable DC: 13.8 Volt, 5 amp Regulated Power Supply with Cigarette Lighter Receptacle (PS138V5A) or 25 Amp Variable Volt Power Supply with Digital Readout (PSVPW25A)
    • Counterweights: Stainless Steel Counterweights - 5, 10, and 18-pounds. (5SCWT, 10SCWT, 18SCWT)

    Additional Accessories to Consider

    • TO Keypad with 15-foot Coiled Cable and Keypad Protector (KEYVFK)
    • Astro-Physics Command Center Pro (APCC Pro) software
    • Right-Angle Polar Alignment Scope with Illuminator (RAPAS)
    • Pier Accessory Trays and Support Bar
    • 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)

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