Additional photo to view:
900GTO German Equatorial Mount (900GTO)
with GTOCP2 Control Box
Includes Go-to Keypad Controller and DigitalSky Voice™ software
The 900GTO German
Equatorial Mount with the GTOCP2 Control Box is
not available to purchase. Please refer to information
regarding our current
model of the 900GTO if you are interested in
a new mount. This information is provided for present
owners and those who are curious about its history. It is based on original information with some updates.
If you are one of the lucky owners, you may want
to consider some of these accessories or upgrades.
If you are interested in some of the earlier models,
check out this Brief
History of the 900 German Equatorial.
900GTO with 155mm f7 StarFire EDF(4" focuser model), 15" Ribbed Plate, 80mm Guidescope and other accessories
||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. The largest of these is our 1200GTO and the next in line is the 900GTO. If your instrument of choice is a medium-sized refractor, Cassegrain, Ritchey-Chretien, Newtonian or astrograph, we invite you to read on.
|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 Mount Pinos in California, favorite observing site 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.
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:
Write your own computer program.
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.
- 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 software 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 device!
- Separate computer control.
All functions of the servo drive can be commanded from a laptop or desktop computer using popular planetarium 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:
- 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 6 by Chris Marriot
- DigitalSky Voice by Charles Sinsofsky (included
with the 900GTO)
The Astro-Physics GTO
protocol for the GTOCP2 Control Box is freely available
to those who would like to write their own computer
program for controlling the mount. While based on the
Meade protocol, it has many more features and enhanced
precision level which allows pointing and tracking to
the 1 arc second level.
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 accuracy
Critical worm gear accuracy
is maintained by special machining techniques developed
at Astro-Physics after extensive studies and actual
field operation. Our worm accuracies are second to none.
With good alignment, PEM training with the Keypad or
by using PEMPro
software, it is quite practical now to achieve unguided
CCD images with today's hi-resolution cameras coupled
to a 6" to 12" telescope.
of Equatorial Head
- All machined mounting made from aluminum barstock and stainless steel. All fasteners are stainless steel.
- Motors and all electronic components are enclosed
- Ball bearing races.
- Removable 1.875" diameter counterweight shaft.
- 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
- Electronic components rated for industrial and automotive applications
- Base fits into 8" outside diameter pier with 0.125" wall thickness
R.A. worm wheel
7.2" (18.3cm), 225 tooth aluminum
Declination worm wheel
6" (15.2cm), 225 tooth aluminum
R.A. thrust surface
Declination thrust surface
6.0" (15.2cm) diameter
2.2" (5.6cm) diameter
1.75" (4.4cm) diameter
20 to 68 degrees
0 to 20 degrees with latitude wedge Azimuth adjustment
Approximately 14 degrees
Porter Slip Ring design, engraved
4 minute increments, pointer, engraved both Northern/Southern
1 degree increments, pointer
Approximately 70 lbs. (31.8kg) scope and accessories, depending on length. Will accommodate Astro-Physics and similar refractors up to 180mm f9, 12" Cassegrains, 12-14" Ritchey-Chretiens
Some telescopes are very heavy for their size and will require a larger mount.
Weight of equatorial head
50 lbs (22.2kg), Declination axis is 15 lbs. (6.8kg) right ascension axis is 25 lbs.(11.4kg), counterweight shaft is 10 lbs. (4.6kg)
Servo Motor Drive
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 guiding to
1200x sidereal for 5 degree per second slewing. The
circuit draws only 0.4 amps when tracking the stars,
2 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.
Please refer to GTOCP2
Control Box and Keypad for Servo Drive for additional
Improving the Performance of
Firmware - Keep your keypad up-to-date with
the latest firmware downloaded directly from our
website free of charge.
- 900 Upgrades and Spare
Parts - Includes 900 Pier Adapter Plate (900SPA), wedge for 0-20 degrees latitude and other replacement parts. We may have additional upgrade parts available in 2005.
- Electronics - Upgrade to the new GTOCP3 Control Box or purchase a spare Keypad or cables.
Software - This powerful utility by Ray Gralak
of Sirius-Imaging provides complete remote control
of all Astro-Physics GTO mounts, from the 400GTO
to the 1200GTO. It derives its name from its most
distinctive feature, pulse guiding, which can improve
unguided tracking. This program is offered free of charge.
Software - PEMPro (Periodic Error Management
Professional) is a Windows software application
that makes it easy to characterize and reduce periodic
error in order to maximize performance without auto-guiding.
This software was also written by Ray Gralak and
distributed by CCDWare.
DigitalSky Voice is a terrific observing companion offering lots of observing ideas and information. If you plan to use an IBM-compatible personal computer to control your telescope, you will have lots of fun with this program. The software is included with the mount. Please refer to DigitalSky Voice Software for additional information.
||The diagram shows several dimensions that are commonly requested. In addition, if the scope is horizontal and pointing west or south, the measurement from the top of the pier to the middle of the cradle plate is 11.25." Please note that these dimensions will vary somewhat depending on your latitude. We quote them for 42 degrees because that is the latitude of Astro-Physics and all of our equipment is set up that way. It is also a good average value.
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- Advanced Telescope Systems (ATS) Portable Piers - 8" diameter, heights 24", 30" 36", 42", 48", 54"
- Santa Barbara Instrument Group ST-4, ST-6, ST-7 and ST-8 CCD Star Tracker/Imaging Systems
- Mounting Plates- FP1800, DOVE15, DOVELM, 900RP,DOVE08 with Q4047
- Astro-Physics Portable Pier - 8" diameter, heights 24",32",42",48",54",62
- 900 Wedge for 0-20 Degrees Latitude (900WDG)
- Stainless Steel Counterweights – 10, 18 lbs
- Jim's Mobile Inc. Digital Setting Circles
- Cable for SBIG ST-4, ST-6, ST-7, ST-8
- Pier Accessory Trays and Support Bar
Counterweight Shaft (M12601-B)
- Pier Adapter Knob Kit for 900 Mounts
Base/Pier Adapter (900SPA or 900RPA))
- Encoders for Digital Setting Circles
Software by Ray Gralak
- Mounting Rings
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Copyright © 1999-2005, Astro-Physics, Inc. - All Rights Reserved
This page was last modified:
February 23, 2011
11250 Forest Hills Road, Machesney Park, IL 61115, U.S.A.
Phone: 815-282-1513 Fax: 815-282-9847