Astro-Physics 1600GTO Computerized German Equatorial Telescope Mount

Brand: Astro-Physics

SKU : AP-1600GTO

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  • For time frames or questions, please contact us at 800-483-6287.
  • The Astro-Physics 1600GTO Equatorial Mount is an observatory-grade mount with a weight capacity of 220 lbs
  • Manufactured & assembled in the USA and individually tested to exceed periodic error specification of 5 arc seconds (+/- 2.5 arc sec.)
  • Altitude range extends from 0 to 78-degrees
  • Larger motors for increased torque in cold temperatures
  • Very low backlash gear train eliminates Dec reversal delays and provides high position accuracy during guiding
  • Absolute Encoders upgrade available to virtually eliminate periodic error, reducing it below 0.2 arc-seconds
  • This product has a flat shipping charge of $440 for contiguous states (AK, HI and international destinations will be more)

Product Details

  • The AP 1600GTO mount is built from the ground up to be a precision imaging platform while still remaining totally user-friendly. Consider these advantages and features:

    Thirty plus years of mount design and building expertise, plus actually using the equipment, has been employed to engineer and build the Astro-Physics 1600GTO into the most robust, high-precision German equatorial mount in its class.


    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 available via direct downloads.

    Auto-Adjusting Motor/Gearboxes:  The new motor/gearboxes were designed to be more responsive for precision astrophotography, while at the same time making it super easy to use and adjust. The photo for the new motor/gearboxes is not available at this time. Refer to the photos shown for the 1100GTO for a close approximation.

    Key features:
    • For time frames or questions, please contact us at 800-483-6287.
    • 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 gear train eliminates Dec reversal delays and provides high position accuracy during guiding
    • Gear train 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-percent of the variability even in non-encoder mounts.

    Features of the 1600GTO (as compared to the 1200): 

    • For time frames or questions, please contact us at 800-483-6287.
    • Dec. axis gear increased to 10.3-inchesfor higher payloads and more stability
    • Azimuth adjusters have been repositioned to the rear of 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.
    • Built-in precision-rotating pier adapter is now included and not purchased as a separate item.
    • Major altitude adjustments are extremely easy to make. Simply shift the position of the bar into a new slot without having to line up obscure holes referenced in the manual. The large "captain's wheel" knob is also very easy to grasp and turn. If you travel to a star party at a different latitude, you can make changes to your setup very quickly. This also allows you to transport the RA assembly in a more compact, zero degree latitude configuration.
    • Altitude range now extends from 0 to 78-degrees, which makes it suitable for most anyone except the extreme polar locations. The Hi-Low Wedge is no longer necessary.
    • 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.
    • Easily route additional cables 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.
    • Right-angle connectors are used in most locations to reduce strain on the cables.
    • Larger motors for increased torque in cold temperatures. These are the same motors as used in the current 3600GTO mount. Note: The 1200GTO mounts produced in 2011 also have these motors.
    • Improved clutch system with NO clutch plugs that can potentially deform with time if they are over-tightened. 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.
    • Control box mounted on the side rather than the top to reduce the possibility of moisture getting into the electronics in damp environments.
    • Greater capacity to provide a rigid platform for fairly large instruments or side-by-side setups.
    • Absolute Encoder option to provide error-free tracking, software readable absolute position, customize-able home and limit functions for robotic imaging. This option can be installed whenever you are ready to take advantage of its capabilities.


    Astro-Physics 1600GTO = Versatility: 

    Portable: The AP 1600GTO is an 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, it is suggested that a minimum 5 amp filtered-regulated power supply (like their 13.8-volt, 5-amp Power Supply -PS13V5A). For a heavy payload in cold conditions, they offer a 15-volt, 12-amp power supply -PS15V12AC.

    Clutches: Allow manual operation if power is not available. 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.

    Image past the meridian: The 1600GTO 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. This feature of AP GTO mounts has been a real customer favorite:

    "The 1200GTO's ability to continue tracking when past the meridian is an absolute winner for me. It avoids meridian flips (=imaging time) and reduces the need for expensive rotators." - Jan Rek

    ". . . I love the ability to place the OTA on the "wrong side" of the mount when starting an imaging session ("premature meridian flip") and which I have used extensively. This feature is pure INGENUITY!" - Anthony Ayiomamitis.

    Easy alignment for non-critical viewing:  You can align the 1600GTO using setup routines in the keypad, or with a polar alignment scope to quickly zero in on the pole for most non-critical observing or to get close before tweaking in for imaging (polar scope sold separately). You can even align the mount during the day with the 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 Your Observatory: You have your choice of using the GTO Keypad (optional), which is a full-featured handheld computer, PC computers using a wide variety of software with or without the ASCOM driver, Mac computers using a nice choice of software, or even your mobile smart device (like your iPhone or iPad). The Astro-Physics command language is available to those who need to write their own software.


    The 1600GTO Mount's Mechanical Features:

    Precise Mechanical Fabrication: Using modern CNC machining techniques, they manufacture 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 mount is straightforward with modular construction and no complicated internal wiring.

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

    GTOCP4 Servo Drive System: Like the previous mounts, these drive systems use a high-quality, heavy-duty Swiss DC servo motor controlled by a microprocessor to an accuracy of 0.05 arc-seconds per step. Tracking is very smooth, noticeably smoother than any stepper motor drive or inexpensive servo motor. The system can be accurately 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 astroimager, 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 5 arc seconds (+/- 2.5 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 integral 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 5 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 5 arc seconds (+/- 2.5 arc sec.) is the maximum native mechanical error inherent in the mount's RA axis WITHOUT any software correction. In order optimize performance even further, we use a special version of Ray Gralak's PEMPro (described below) developed specifically for our test equipment. Astro-Physics generates a unique PE curve for each mount which is programmed 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 5 arc second spec without additional PEMPro runs! However, you may use PEMPro to further refine your PE, if you chose to do so.

    GTOCP4 Control Box: The GTOCP4 Control Box 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 1600GTO uses the same GTOCP4 Control Box as the 1100GTO and Mach1GTO (the control box is black-anodized for the latter mount). 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.

    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. AP has 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.

    Prior to mid-October 2015, the Keypad was included as part of the mount. However, some customers own multiple AP mounts, but only use one at a time. For them, one keypad is sufficient. Others only control their AP mounts with their computer and do not use their Keypad. So, AP decided to offer the Keypad as an option. As a result, they were able to reduce the price of the mount accordingly.

    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. They will choose to purchase the Keypad.

    PEMPro Software, Version 2: PEMPro (Periodic Error Management Professional), Version 2, 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 or the PulseGuide 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.

    Pier Mounting Options: The 1600GTO 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 1600GTO and all 1200 Mounts (1612FSA). When choosing the Advanced Telescope System's (ATS) Pier, you will need to order the AP Flat Surface Adapter with Flat Pier Plate 1612FSA-FP that will fit into the top of their pier. The 1600GTO's large adjustable 0 to 78-degree latitude range (which spans from Antarctica to the arctic circle) makes the use of a wedge unnecessary.


    GTOCP4 Servo Drive System Specifications:

    Electronic components Rated for industrial and automotive applications
    Motors High-torque, 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

    5 arc seconds peak-to-peak (+/- 2.5 arc seconds) or less in one worm cycle (6.4 minutes); native, prior to any error correction

    Maximum slew speed 5 degrees / second

    Items that You will Need for Your Mount: 

    • Counterweight: Stainless Steel Counterweights - 5, 10, 18, 24-pound
    • Saddle Plate: DOVELM162, DOVELM2, DOVEPW, 1200RP, FP1800, DOVE15
    • D-Style (3-inch) Dovetail Plate: Check out our wide selection of D-Style Dovetail Plates, 13-inch and 16-inch Side-by-Side Plates (SBD13SS and SBD16SS) and Vixen Dovetail Converter (SBD2V)
    • P-Style (7.65-inch) Dovetail Plate: 23-inch PlaneWave Style Dovetail Plate (SBPW23)
    • Pier: Astro-Physics Portable Pier: 10-inch diameter, heights 24 , 32 , 42, 48, 54, and 62-inches, Advanced Telescope Systems (ATS) Portable Pier or build your own permanent pier
    • Regulated Power Supply: 13.8-volt, 5-amp (PS138V5A) or 15-volt, 12-amp (PS15V12AC) Regulated Power Supply with Cigarette Adapter
    • Portable Rechargeable 12Volt 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! It is recommended that you have separate batteries, one for the mount and another for all other accessories: camera, dew removers, etc.
  • specifications

    Encoder Resolutionseconds per step
    Encoder Type2000 tic quadrature
    Head DesignEquatorial
    Instrument Capacity220 lb
    Latitude Range0 to 78 Degrees
    Pointing Accuracy 2.5Arcsecond
    Pointing Accuracy<1 Arcsecond
    PortsUSB 2.0
    RA Worm262mm Diameter 225 Teeth
    Slew Speed5 degrees / second
  • included items

    • Astro-Physics 1600GTO Computerized German Equatorial Telescope Mount
    • For time frames or questions, please contact us at 800-483-6287.

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