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.

Three versions are available: 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.

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 Adjustments Are Convenient And Quick

• Major altitude adjustments are extremely easy to make by simply shifting the position of the altitude adjustment bar into a new slot. The large "captain's wheel" knob, convenient to grasp and turn, performs the fine adjustments. If you travel to a star party at a different latitude, the changes to your setup are quickly made and allow you to transport the RA assembly in a more compact, zero degree latitude configuration.
• Azimuth adjusters are located at the rear of mount which allows you to make minor corrections quite easily. Since the knobs are in front of you as you look through the polar scope, the graduations can be more easily seen as you dial in your position.
• Built-in precision-rotating pier adapter for smooth azimuth adjustments.

Through-The-Mount Cabling

The RA and Dec motor cables are routed internally to reduce the possibility 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

AP's 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).

Auto-Adjusting Motor/Gearboxes

AP's 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
  
  

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, AP makes 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. AP provides information in the Technical Support section of their 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.

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 0.5 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.

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 AP's facility and individually tested to meet or exceed their 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 AP's 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 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

GTO Servo Drive Specifications

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, AP's 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.

Absolute Encoders for your 1100GTO

The 1100GTO mount has been designed and engineered to accommodate extremely precise Absolute Encoders. These are the same encoders as are used on the 1600GTO. We invite you to review the technical information regarding the encoders and find out what they can do for you.  

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 arc seconds in AP's 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.

1100GTO: 1100GTO German Equatorial Mount

• Polar Fork / Right Ascension Axis (R.A.) Assembly
• Declination Axis (Dec.) Assembly
• GTOCP4 Servo Control Box
• Control Box Adapter
• 16.675" Stainless Counterweight Shaft, 1.875" diameter (M9404-B) and Safety Stop (M12676)
• 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 (CABPP4SET)
• 15' Straight-through Serial Cable (CABSER15)
• Allenhead wrench set
• CD containing: PEMPro v3 Software written by Ray Gralak of Sirius Imaging. Also, PDF of 1100GTO and GTO Keypad instruction manuals
• Manual: 1100GTO German Equatorial
• Manual: GTOCP4 Servo Motor Drive System
• Registration Card
• ** Special offer **: Astro-Physics Command Center (APCC) Standard Software is included

1100GTO-AE: 1100GTO German Equatorial Mount with Absolute Encoders (Standard Temperature Range

• All items listed above for the 1100GTO
• R.A. and Dec. Absolute Encoders, installed
• R.A. and Dec. Readhead with wire harness, standard temperature version, installed
• Junction Box and Cables
• Dec Axis Encoder Guard
• All required fasteners
• ** Special offer **: Astro-Physics Command Center (APCC) Pro Software is included
• All accessories that are listed as suitable for the 1100GTO are appropriate for this version of the mount, as well, with the exception of the Limit/Homing Switch System, which would not be needed anyway.

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

• All items listed above for the 1100GTO-AE, except that the Readheads are the Extended Temperature Version.
• All accessories that are listed as suitable for the 1100GTO are appropriate for this version of the mount, as well, with the exception of the Limit/Homing Switch System, which would not be needed anyway.

Items that You will Need for Your Mount

• Counterweight: Stainless Steel Counterweights - 5, 10, 18 and 30 lb.
• Saddle Plate: DOVELM162, DOVEDV10, 900RP, FP1800, DOVE15
• D-Style (3") Dovetail Plate: Check out our wide selection of D-Style Dovetail Plates, 13" and 16" Side-by-Side Plates (SBD13SS and SBD16SS) and Vixen Dovetail Converter (SBD2V)
• Pier: Astro-Physics Portable Pier - 8" diameter, heights 24",32",42",48",54",62", Advanced Telescope Systems (ATS) Portable Pier or build your own permanent pier
• Regulated Power Supply: 13.8-volt, 5-amp (PS138V5A) or 25 Amp Variable Volt Power Supply (PSVPW25A) Regulated Power Supply with Cigarette Adapter
• Portable Rechargeable 12-volt Battery Pack: Several sizes and types are available from a variety of vendors. Be sure that your battery pack can supply adequate power for an entire observing session! We recommend having separate batteries - one for the mount and another for all other accessories: camera, dew removers, etc. We do not offer any battery packs at this time.

Additional Accessories to Consider

• GTO Keypad with 15' Coiled Cable and Keypad Protector (KEYVFK)
• Absolute Encoder Upgrade Kit
• Right-Angle Polar Alignment Scope with LED Illuminator - 1600GTO, 1100GTO, Mach1GTO and all 900 and 1200 Mounts (RAPAS)
• Losmandy Polar Alignment Scope with LED Cable for 1100GTO and 1600GTO (PASILL4L-179)
• Losmandy Polar Alignment Scope Adapter for 1100GTO and 1600GTO (Q16030)
• 8.675" Counterweight Shaft Extension (M12675)
• Flat Surface Adapter (119FSA)
• Flat Surface Adapter with Flat Pier Plate for 1100GTO and all 900 Mounts - For 8" ATS and other non-Astro-Physics piers (119FSA-FP)
• Pier Accessory Trays and Support Bar

US Shipping costs are $330.  International shipping extra.