Astro-Physics GTO-1100 Mount (various versions available)

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Astro-Physics GTO-1100 Mount (various versions available)

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€ 15,500.00 Price excl. German VAT tax (19%): € 13,025.21

  • German Equatorial Mount with Servo Motor Drive
  • the R.A. and Dec. axes split easily for a more comfortable assembly and / or transport - load easily a telescope (configuration) of over 110 lb. (50 kg)
  • with GTOCP4 Control Box and Auto-Adjusting Motor/Gearboxes, optional GTO Keypad available
  • optional with Encoders in R.A. und Dec Axis available - various versions at the dropdown below
Important note: This product is not available online. If you are interested, please send us a formal inquiry incl. contact data by email. We shall gladly provide a detailed offer.

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€ 15,500.00 Price excl. German VAT tax (19%): € 13,025.21

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Astro Physics 1100GTO S&T Hot product

Astro-Physics GTO-1100 German Equatorial Mount

with GTOCP4 Control Box and Auto-Adjusting Motor/Gearboxes

The GTO-1100 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 GTO-1100 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: GTO-1600 German Equatorial mounts with discussion of the Absolute Encoder System used in both the GTO-1100 and GTI-1600 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.

The GTO-1100 mount offers more and improved features compared to its predecessor 900GTO. Since the introduction of the 900 German Equatorial Mount in the mid 1990s, the new GTO-1100 is the next step in that evolutionary process offering increased capacity, ease of setup and use and enhancements to make your imaging sessions more productive and enjoyable.

Sky & Telescope Test Review

Test Report:

"The Astro-Physics GTI-1100: This powerful German equatorial mount offers many features for astrophotographers." Read the S&T test report from July 2017.

The GTO-1100 at a glance:

But the most important feature first...


Astro-Physics has designed new motor/gearboxes for all Astro-Physics mounts - also for the GTO-1100. The motor/gearboxes were designed to be more responsive for precision astro-photography, while at the same time making it super easy to use and adjust. Here are some key features:

  • Spring-loaded worms maintain full contact under all guiding and slewing conditions
  • Automatic setting for worm mesh requires no adjustments over long time periods
  • Very easy to do precision balance by new mechanism which 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
  • Geartrain components are made with high-strength stainless alloy for extremely low wear even with continuous slewing applications
  • Worms made with high-strength alloy eliminates wear during long periods of slewing, especially useful for remote setups that do survey work
  • All worms are tested to meet stringent periodic error specs. Error is measured with PEMPro and the resultant compensating curve is loaded into the servo controller so you can use the PEM function to remove 90% of the variability even in non-encoder mounts.
AP GTO1100
Some more highlights ...
  • completely redesigned CTOCP4 Control Box with modern chip technology resulting in faster processing speed and increased memory capacity for future feature additions. More information about the GTOCP4 Controll Box are available here.
  • Dec. axis gear increased to 7.2" (183mm) for higher payloads and more stability
  • the R.A. and Dec. axes split easily for a more comfortable assembly and / or transport. The connection of the two components is achieved by a CNC-machined dovetail receptor clamp. The R.A. axis/polar fork weighs 27.6lb (12.5kg) and the DEC axis 15.6lbs (7.1kg). Thus, the GTO-1100 can still be described as a transportable mount.
  • Azimuth adjusters have been repositioned to the rear of the mount which allows you to make minor corrections quite easily without reaching or moving around the mount. Since the knobs are now in front of you as you look through the polar scope, the graduations can be more easily seen as you dial in your position. Azimuth adjustment: +/- 9 degrees from center
  • built-in precision-rotating pier adapter is now included and not sold as a separate item
  • altitude range now extends from 0-78 degrees in its normal configuration
  • Right-Angle Polar Alignment Scope (optional) can be used without the need for an additional adapter. Unobstructed Dec. opening for Polar Alignment Scope allows greater field of view for both the Astro-Physics Right-Angle or the Losmandy Style Polar Alignment Scopes
  • internal routing of motor cables to remove the possibility of snagging
  • eaesy to adjust and maintain. All components are modular
  • Precision bubble level built into mount base
  • improved clutch system with NO clutch plugs that can potentially deform over time if they are overtightened. This issue has been eliminated. Clutch can be set to any amount of engagement up to complete locking of the axes so nothing can slip.
  • greater capacity to provide a rigid platform for fairly large instruments or side-by-side setups. The mount loads easily a telescope (configuration) of over 110 lb. (50 kg)
  • Control box mounted vertically rather than on the top to reduce the possibility of moisture getting into the electronics in damp environments
  • Limit/Homing Switch option to provide home and limit functions using a mechanical switch (does not use the absolute encoders)
  • 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
  • manufactured modern CNC machining techniques. 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
  • operates with 12V battery. In the observatory, we suggest a minimum 5 amp filtered, regulated power supply like a 13.8-volt, 5-amp Power Supply
  • multiple options for controlling your mount in the field or in 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)
CP4 Control

Detailed information about the GTOCP4 is available here

For detailed information please visit the original website of Astro Physics. If you have any further questions, please send us an email to kontakt (at) or call us.

We also offer two versions of the GTO-1100 German Equatorial Mount with Absolute Encoders:

Astro Physics 1100 GTO
  • GTO-1100 German Equatorial Mount with Absolute Encoders (#1401406)
  • GTO-1100 German Equatorial Mount with Extended Temperature Range Encoders (#1401407)

The GTO-1100 mount has been designed and engineered to accomodate extremely precise Absolute Encoders. These are the same encoders as are used on the GTO-1600.

Absolute Encoders allow the mount to know its exact location regardless of accidental software errors and will allow its recovery. This is particularly important in remote setups. Furthermore, they virtually eliminate periodic error, reducing it below 0.2 arcseconds in our tests. If you order the 1100GTO-AE or 1100GTO-AEL, the R.A. and Dec. encoders will be installed and fully tested with the mount prior to shipment.

However, if you purchase the GTO-1100 without encoders, you may purchase the Absolute Encoder Kit and install them yourself.

Check out the 10 minute (600 seconds) unguided exposure by clicking on the thumbnail to the right. Note that this image was taken with the 1600GTO, but as mentioned earlier, the same encoders are used on the 1100GTO, so the performance is representative.

GTOCP4 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 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. More information about the GTO Keypad is available here.
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 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

For more detailed information please visit the original website of Astro Physics. If you have any further questions, please send us an email to kontakt (at) or call us.

Detailed information about the Astro-Physics German Equatorial Mount are available here.

What's included (standard version):

  • Polar Fork / Right Ascension Axis (R.A.) Assembly
  • Declination Axis (Dec.) Assembly
  • GTOCP4 Servo Control Box
  • Control Box Adapter
  • 14" Stainless Counterweight Shaft, 1.875" diameter and Safety Stop
  • R.A. and Dec. Y-Cable
  • Power Cable Set for GTOCP4, includes 6' Cable with PowerPole Connector, 18" Cable with Cigarette Lighter Plug and 18" Cable with Ring Terminals
  • 15' Straight-through Serial Cable
  • Allenhead wrench set
  • CD containing: PEMPro v2 Software and PulseGuide Software, both written by Ray Gralak of Sirius Imaging. Also, PDF of 1100GTO and GTO Keypad instruction manuals
  • Manual: 1100GTO German Equatorial and GTOCP4 Servo Motor Drive System
  • Registration Card

If you have any further questions, please send us an email to kontakt (at) or call us.


Applies to all mounts which are controlled through plug connections of hand controllers and / or through plug connections with electronic accessories.

Again and again, we receive mounts for repair work, which have malfunctions due to corroded connections. Therefore, the following note:

The plug-in connections at all contact points in astronomical telescopes are generally exposed to humidity and dirt. For the current transmission on such plug-in connections there is often a higher risk of damage due to humidity or corrosion as is ussually the with plug-in connections in the household.

It is advisable to spray the connectors of all cable connections generously with contact spray and then plug in the respective plug several times. In this way, the contact is cleaned and at the same time corrosion and the accumulation of condensation water are prevented. Please do not spray into the socket! In this way, short circuits can be produced if contact liquid is used too generously and runs through electronic components inside the device.

In any case, if there are undefined malfunctions during the electricity or signal transmission, it is first of all advisable to clean the plug-in connections by means of contact spray.

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Michael Karrer 141/05/2019 22/05/201910:56
  • Rating:
Erfahrung mit der Montierung Astro-Physics GTO-1100
Wer die Präzision von Astrophysics schätzt, erfährt mit dem Nachfolgemodell eine nochmalige Steigerung. Unser Hobby soll uns in den Stunden unter dem Himmel Freude bereiten, die komplexer gewordene Technik soll nicht verwirren oder gar frustrieren, sondern uns unterstützen. Hohe Qualität kostet, ja, aber sie garantiert Spaß, Entspannung und schöne Ergebnisse. Dafür steht für mich Astro-Physics!
Herr Karrer hat uns einen ausführlichen Testbericht zur Verfügung gestellt, von welchem wir hier nur das Fazit zitieren.
Den gesamten Bericht können Sie hier lesen:
Erfahrung mit der Montierung Astro-Physics GTO-1100
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