ASTRO-PHYSICS
1100GTO German Equatorial Mount
with
GTOCP4 Control Box
Auto-Adjusting Motor/Gearboxes

Your choice of three models:
1100GTO German Equatorial Mount (1100GTO)
1100GTO German Equatorial Mount with Absolute Encoders (1100GTO-AE)
1100GTO German Equatorial Mount with Extended Temperature Range Encoders (1100GTO-AEL)

* * Save $1,000 on Mounts with Absolute Encoders * *
   

1100GTO

1100GTO-AE or 1100GTO-AEL

Read the Sky & Telescope July 2017 review by clicking on the link above.

Why an 1100GTO?

The 1100GTO is a mid-sized observatory-class mount that will provide reliable operation in your distant, remote observatory *** or *** eagerly travel to star parties where your 12V battery will keep it running all night.

We offer three versions: 1100GTO, 1100GTO-AE and 1100GTO-AEL. The latter two versions include the Standard Temperature Absolute Encoders or the Extended Temperature Absolute Encoders, respectively. If you order the 1100GTO without the absolute encoders, you will be able to purchase them at a later date to install yourself.

This webpage discusses the features that are common to all three mount versions, except where indicated.

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.

Features to Enhance your Observing or Imaging Sessions

Portable
Extremely solid, rugged, high payload mount, yet the equatorial head comes apart into two components for hassle-free field setup.

Operate with 12V battery
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 like our 13.8-volt, 5-amp Power Supply (PS138V5A). For a heavy payload in cold conditions, we offer a 25 Amp Variable Volt Power Supply (PSVPW25A)

Azimuth and Altitude Adjustment is convenient and quick

Through-the-mount cabling
The RA and Dec motor cables are routed internally to reduce the possibiity of snagging. Additional cables can pass through the large openings in the R.A. and Dec. axes. The top of the Dec. axis separates so that you can add cables with large connectors.

Clutches
Use the clutches to easily balance your setup, then lock the R.A. and Dec. axes so that they cannot move when the motors are engaged. Manual operation is possible if power is not available.

Image past the meridian.
The mount will track and guide well past the meridian in either direction if the object is located so 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. This feature of our GTO mounts has been a real customer favorite for many years.

Easy polar alignment for critical viewing
Our optional Right-Angle Polar Alignment Scope will allow you to quickly zero in on the pole or the polar alignment routine in PEMPro (included) 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 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). Follow this link to discussions of GTO control options.

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.

Absolute Encoder option
Absolute Encoders on both axes provide error-free tracking, software readable absolute position, customizable home and limit functions for robotic imaging. This option can be installed when you purchase your mount (order either the 1100GTO-AE or 1100GTO-AEL version) or you can purchase the option as an upgrade kit when you are ready to take advantage of its capabilities.


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. Massive thrust bearings and preloaded shaft bearings provide excellent stability under all imaging situations.

Easy to Adjust and Maintain
The design of the 1100GTO is straightforward with modular construction. We provide information in the Technical Support section of our website pertaining to typical adjustment issues.

Components are modular
All electronics including the GTOCP4 control box, motors, gearbox or cables can be removed for servicing. The RA and Dec axes can be shipped separately, if needed.

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. 7.2" (183 mm), 225 tooth aluminum
Worm gear - R.A. & Dec. 0.71" (18 mm) diameter
Axis shaft - R.A. & Dec. 3.15" (80 mm) diameter
Shaft axis bearings - R.A. & Dec. 3.94" (100 mm) diameter
Latitude range 0 to 78 degrees
Azimuth adjustment Approximately 18 degrees (+/- 9 degrees from center)
Counterweight shaft 1.875" (47.6 mm) diameter x 16.5" (419 mm) usable length, incl. large machined safety stop knob. Optional 8.675" (220 mm) shaft extension available. Weight 13 lb. (5.9 kg)
Weight of mount

R.A. axis/polar fork: 27.6 lb. (12.5 kg)
Dec. axis: 15.6 lb. (7.1 kg)
Dec. top plate 1.5 lb. (0.7 kg)

Capacity Approximately 110 lb. (50 kg) of scope and accessories, depending on length. Recommended for refractors up to 200 mm, 14-16" Cassegrains, Ritchey-Chretiens and CDKs.

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
Pier adapter base diameter 7.730" (196.3 mm) Base. The base is an integral part of the mount and azimuth adjuster.

GTOCP4 Servo Drive System

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 0.5 amps when tracking the stars, 2.5 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.

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 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.

1100GTO-AE or 1100GTO-AEL: If you purchase either of these versions that feature absolute encoders, the final in-house PEMPro run will utilize the corrections of the absolute encoders and the values will be stored in the GTOCP4 Control Box.

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 the 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. Extensive information regarding the GTOCP4 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. 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. Click here for detailed information regarding features and functions of the Keypad.

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. 


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 1100GTO. Dennis DiCicco, editor of Sky & Telescope magazine,opens the interview with a discussion of the 17" f8 Flat Field Astrograph.

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
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

Absolute Encoders - 1100GTO-AE and 1100GTO-AEL


10 minute unguided exposure

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

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 1100GTO without encoders, you may purchase the Absolute Encoder Kit at some point in the future and install them yourself.

Check out the 10 minute (600 seconds) unguided exposure by clicking on the thumbnail to the left. 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.

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-sze 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.

Pier Mounting Options

The 1100GTO mount integrates a precision rotating pier adapter and azimuth adjuster as part of its base. The mount's base will directly attach to the Astro-Physics pier, or it can be attached to any flat surface using the Flat Surface Adapter for 1100GTO and all 900 Mounts (119FSA). If you plan to use an 8" ATS pier, you will need the Flat Surface Adapter with Flat Pier Plate for 1100GTO and all 900 Mounts (119FSA-FP). The 1100GTO's wide adjustable 0 to 78 degree latitude range (which spans from Antarctica to the arctic circle) makes the use of a wedge unnecesary.

Dimensions

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.

Support

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 in the ap-ug and ap-gto user groups in the Yahoogroups forum. The user groups are comprised of scope and 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.


Price and Delivery Information

Prices for mounts with Absolute Encoders reflect $1,000 SAVINGS !!

Shipping charges: $275 for ground shipment within the 48 continguous states; contact us for other destinations.

1100GTO German Equatorial
$7,970

1100GTO with R.A. and Dec. Absolute Encoders and Readhead, standard temperature version.
$13,196 ($1,000 savings from normal retail price)

1100GTO with R.A. and Dec. Absolute Encoders and Readhead, extended temperature version.
$13,961 ($1,000 savings from normal retail price)

1100GTO: 1100GTO German Equatorial Mount
What’s Included:

1100GTO-AE: 1100GTO German Equatorial Mount with Absolute Encoders (Standard Temperature Range)
What’s Included:

1100GTO-AEL: 1100GTO German Equatorial Mount with Absolute Encoders (Extended Temperature Range)
What’s Included:

Items that You will Need for Your Mount

Additional Accessories to Consider

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This page was last modified: August 2, 2018

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