|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.||10.3″ (262 mm), 225 tooth aluminum|
|Worm wheel – Dec.||7.2″ (183 mm), 225 tooth aluminum|
|Worm gear – R.A.||Brass, 1.210″ (30.7 mm) diameter|
|Worm gear – Dec.||Brass, 0.710″ (18 mm) diameter|
|Thrust Bearing – R.A.||9.5″ (241 mm) diameter|
|Thrust bearing – Dec.||6.5″ (165 mm) diameter|
|Axis shaft – R.A.||3.35″ (85 mm) diameter|
|Axis shaft – Dec.||2.36″ (60 mm) diameter|
|Shaft axis bearings – R.A./Dec.||Each shaft is supported by 5 bearing elements, two preloaded ball bearings and 3 sets of massive thrust bearings|
|Latitude range||22 to 69 degrees with or without the polar scope attached.|
0-22 or 69-90 degrees when using Hi-Lo Latitude Wedge (1200WDG or 1200WDGA)
|Azimuth adjustment||Approximately 14 degrees (+/- 7 degrees from center)|
|Setting circle – R.A.||4-minute increments, pointer, engraved both Northern/Southern, Porter Slip Ring|
|Setting circle – Dec.||1 degree increments, pointer, engraved, Porter Slip Ring|
|Counterweight shaft||1.875″ (48 mm) diameter x 19.5″ (495 mm) long [18.5″ (470 mm) useable length], incl. large machined safety stop knob. Optional 9″ (229 mm) shaft extension available.|
|Weight of mount||Total: 95 lb. (43.2 kg)|
R.A. axis/polar fork: 50 lb. (22.7 kg)
Dec. axis: 31 lb. (14.1 kg)
Counterweight shaft: 14 lb. (6.4 kg)
|Capacity||Approximately 140 lb. (63.6 kg) scope and accessories (not including counterweights), depending on length. Recommended for: Astro-Physics and similar fast refractors up to our 206 mm f8 Starfire EDF, 16″ Cassegrains and Ritchey-Chretiens, 17″ 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.
|Pier adapter base diameter||9.775″ (248.3 mm) Base. The base is part of the chosen pier adapter, either the Rotating Pier Adapter (1200RPA), Standard Pier Adapter (1200SPA), or the Hi-Lo Latitude Wedge (1200WDGA or 1200WDG). The desired pier adapter must be purchased separately.|
GTO Servo Drive System
The 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, 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 astrophotographer, 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 5arc 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. We generate a unique PE curve for each mount that we program into each GTOCP3 Control Box. Simply use the 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.
GTOCP3 Control Box
The GTOCP3 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 1200GTO uses the same GTOCP3 Control Box as the 900GTO 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.
The Keypad is a self-contained computer that allows you to control all essential telescope functions and includes an extensive database of objects. 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.
GTO 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||GTOCP3 Control Box, removeable|
|Hand-held computer||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|