FREE SHIPPING LOWER 48 STATES!

Why a 900GTO?

Stability ... accuracy ... ease of setup ... friendly go-to control interface - these were the primary design goals of the 900GTO. Amateurs today demand a precise mount that will allow them to pursue all aspects of astronomy whether it be observing visually, CCD imaging or photographing with 35mm or 6x7 camera. Many of the finest imagers today have been using our GTO mounts as a solid platform for a wide variety of instruments. Astro-Physics now offers four German Equatorial mounts listed in order of size from largest to smallest: 3600GTO German Equatorial, also known as El Capitan, 1200GTO, 900GTO and the most compact is the Mach1GTO. If your instrument of choice is a medium-sized refractor, Cassegrain, Ritchey-Chretien, Newtonian or astrograph, the 900GTO may be the ideal choice for you.

Since its introduction in 1998, the 900GTO has gained a reputation for both tracking and pointing accuracy, essential to casual visual observation as well as advanced imaging. Quite a few 900GTO and 1200GTO mounts can be found at major star parties throughout the country and the world. It is a favorite of many advanced photographers and imagers. Visit the Cool Sites and Gallery sections of our website to see photos of the mount in action and images taken while using the 900GTO.

These mounts are truly a marvel of engineering - maximum strength and rigidity with minimum weight. Our CNC lathes and mills carve out the excess material in both axes of the 900GTO German Equatorial while retaining a heavily ribbed structure for internal strength and rigidity. A unique dovetail was machined into the mating surfaces of the R.A. and Dec axes. This feature allows quick and easy assembly in the field without any tools.

Over the years, a number of improvements have been incorporated into the design of the 900GTO, among these are smoother azimuth adjusters; increased height of the polar forks to allow more room for your hand when making altitude adjustments; improved gear profiles in the motor gearbox for quieter operation and reduced backlash; motor bracket with built-in spring-action to keep the worms loaded at the proper setting; verifiable worm gear accuracy of 7 arc seconds (+-3.5 arc sec.) or less; internal changes to improve overall accuracy; additional pier adapter options; updated GTOCP3 control box with additional capability; updated keypad with larger memory capacity and LED fiber optic backlit panel; included PulseGuide and PEMPro software as described below. Each time we begin a production run, we ask ourselves what improvements we can make to improve the accuracy and functionality of the 900GTO. As a result, the 900GTO has evolved over the years to meet the needs of the advanced imager or visual observer.

The 900 equatorial is equally at home in a permanent observatory or as a portable mounting for remote star parties thanks to the ease with which the two axes come apart and the reasonable weight of each component - the heaviest is only 25 lbs! Telescopes commonly used include Astro-Physics 155-180mm refractors, 10-11" Schmidt-Cassegrains, 10" Maksutov-Cassegrains and 10-12.5" Ritchey-Chretiens and other scopes of similar size and weight.

The 900GTO mount is built from the ground up to be a precision imaging platform while still being totally user friendly. Consider these advantages and features:

Versatility

Portable.
Extremely solid, rugged, high payload mount, yet comes apart in two reasonably light-weight components for hassle-free field setup. No tools needed to assemble the mount in the field.

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.

Clutches and setting circles.
Allow manual operation 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 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.

Easy alignment for non-critical viewing.
You can align the 900GTO 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 not included. We recommend the PASILL4). 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.

External computer not needed.
The keypad is a handheld computer with all of the features, functions and databases you need to tour the universe night after night. The unique firmware allows you to precisely polar align your mount in the field, even in broad daylight! The vacuum-fluorescent display with a temperature range of -40 degrees F (and C, they are the same in this instance), allows hardy observers to use this mount on cold winter nights. You can't do that with a PC or PDA! As new firmware versions are released in the future, you can upgrade your keypad directly from the download section of our website - free of charge!

Control with personal computer, if desired.
All functions of the servo drive can be commanded from a laptop or desktop computer using popular planetarium programs or PulseGuide software. Depending on the features of the program, you can position your telescope, center your image and control tracking rate, remote focusing, reticle brightness and park at the end of your observing session. Examples of currently available software:

    * PulseGuide by Ray Gralak (included with the 900GTO)
    * Software Bisque's suite which includes TheSky Astronomy Software, CCDSoft CCD Astronomy Software, TPoint Telescope Pointing Analysis Software and Orchestrate Scripting Software.
    * Earth Centered Universe (ECU) by David Lane of Nova Astronomics
    * SkyMap Pro by Chris Marriot
    * Starry Night Pro by Simulation Curriculum Corp.
    * ACP Observatory Control Software by DC-3 Dreams - Robert B Denney
    * Any software that is ASCOM compliant.

Serial to USB connectivity has been simplified by the addition of Keyspan Serial-to-USB devices to our product line.

Write your own computer program.
The Astro-Physics GTO protocol for the GTOCP3 Control Box is freely available to those who would like to write their own computer program for controlling the mount.

Precise Mechanical Fabrication

Highly accurate mechanics
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.

Worm gear accuracyCritical worm gear accuracy is maintained by special machining techniques developed at Astro-Physics after extensive studies, actual field operation and many years of making precision mounts. Our worm accuracies are second to none and are guaranteed to be 7 arc seconds (+/- 3.5 arc sec.) or less peak-to-peak for the 900GTO before introducing any periodic error correction. The periodic error of each mount is verified during our extensive testing procedures. If the PE exceeds these specifications, the faulty part is discarded and another one installed.

Pre-programmed with PEMProPeriodic error corrections for each individual mount are optimized during extensive testing, which results in excellent performance right out of the box. 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. However, in the process of testing the RA axis with a special version of Ray Gralak's PEMPro developed specifically for our test equipment, we generate a unique, optimized PE curve for each individual mount that we program back into that mount. Simply use the Keypad or PulseGuide software to turn PE Correction "on," and you will see results are even better than our published 7 arc second spec! As a historical reference, the first 900GTO mounts that were optimized in this fashion were shipped in 2007.

Mechanical Features

    * All machined mounting made from aluminum barstock and stainless steel. All fasteners are stainless steel.
    * Motors and all electronic components are enclosed
    * Massive thrust bearings and preloaded shaft bearings for excellent stability under all imaging situations.
    * 14" removable 1.875" diameter counterweight shaft (usable length is 12.93") with large machined safety stop knob. Optional 9" shaft extension (M12675) with 8.75" usable length (excludes the length that threads in) is available.
    * Polar and declination axes come apart quickly without tools for light-weight, easy handling and ease of transport
    * Fine altitude and azimuth adjustments for quickly and accurately zeroing in on the pole in the field
    * Engraved setting circles are Porter Slip Ring Design. If your battery runs out of power, you can still find objects.
    * Electronic components rated for industrial and automotive applications
    * Base fits into 8" outside diameter pier with 0.125" wall thickness

Specifications of Equatorial Head

PulseGuide™ Software

PulseGuide is a stand-alone Windows (98, ME, 2000, NT4, XP, Vista and Windows 7) utility that provides complete remote control of the Astro-Physics Mach1GTO, 400GTO, 600EGTO, 900GTO, 1200GTO  and 3600GTO mounts. It derives its name from its most distinctive feature, pulse guiding, which can improve unguided tracking. Specifically, it can help correct tracking errors caused by polar misalignment and atmospheric refraction. You can also train PulseGuide to track objects moving relative to the stars, such as asteroids, comets, and the moon. In addition to pulse guiding, PulseGuide also has many useful utility features. With just a few exceptions, it supports the entire serial Astro-Physics command protocol allowing full control of your mount through your PC. This program is indispensable for remote control of your mount. More information on our website ....

PulseGuide was written by Ray Gralak of Sirius-Imaging. Please refer to his web site http://www.pulseguide.com for further developments and enhancements. The software will be provided on a CD-ROM with your 900GTO mount. Previous owners of any Astro-Physics mounts can download the software free-of-charge, courtesy of Ray. Many, many thanks to Ray for this powerful program.

PEMPro Software, Version 2

PEMPro (Periodic Error Management Professional), Version 2, by Sirius Imaging is a very powerful Windows software application that allows the you to correct your mounts 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 Adapter Options

The 900 Standard Pier Adapter (900SPA) was included with 900 mounts sold in the past. However, in 2005, we decided to offer several choices to meet a variety of needs. We ask that you add one of these options to your mount order. If you plan to have multiple pier installations, perhaps one permanent and another portable, you may wish to purchase an extra adapter to install on the the second pier. This will make your setup and switchover much quicker. Many customers have found this to be advantageous.

If you do not purchase one of our pier adapters described below, for instance, if you purchase the Monolith Pier from Particle Wave Technologies, you will need to purchase the Pier Adapter Knob Kit (part# 9KBKIT) in order to attach your mount to the Monolith.