ASTRO-PHYSICS
3600GTO German Equatorial Mount (3600GTO)
and
3600GTO German Equatorial Mount with Precision Encoder (3600GTOPE)
" el Capitan "
Featuring GTO Servo Drive System
Includes GTOCP3 Control Box, GTO Keypad and CD with PulseGuide and PEMPro v.2 software (full version)
Solid as a rock!
El Capitan is the ultimate imaging platform for large instruments:
RC Optical Systems - 20" or 24" Ritchey-Cretiens
PlaneWave Instruments - CDK17, CDK20, or CDK24
Optical Guidance Systems - RC20 or RC24 or instruments of similar size.
Setups that employ smaller multiple instruments would also be ideal.
The 3600GTO is not available at this time. The information on this webpage if for historical reference only.
Why a 3600GTO ?
The 3600GTO is the culmination of over 30 years of experience designing and building mounts at Astro-Physics for the amateur and professional astrophotographer. We take great pride in the soundness of our designs, the quality of our workmanship and unparalleled support of our customers.| "I am in the process of planning a trip to the remote observatory I own at Arizona Sky Village. I realized that the last time I was there was to install the AP3600GTO in April of last year, and that since that time it has been operating every clear night and has not missed a beat ...The mount has been running for over one year and surpassed my expectations in every way". David Churchill. Read more of his comments here. |
Mechanical Features
Image past the meridian.| . . . 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., More... (commenting on his 1200GTO that uses the same control system. All AP mounts have this feature!) |
Full 360 degree rotation of both axes.
The full 360 degree rotation of both of the 3600GTO's axes also allows this mounting to be placed onto an astrographic pier for complete freedom from movement restrictions. Contact ATS (Advanced Telescope Systems) to discuss astrographic piers.
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Through-the-mount cabling capability. We designed this mount to allow cabling to be run through the axis shafts for tangle and clutter-free operation. Cables from cameras, guiders, dew heaters and the mount's own servo drive cables can all be run through the mount's cavernous 4" hollow shafts where they are out of the way and where they won't ever get caught or tangled during your imaging session. Ports have been included for the mount's servo cables. Additional ports can be added by the user, as needed. |
Components are modular and easy to maintain. Integrated Pier Adapter For most installations, we recommend using our 3600 Flat Surface Adapter (3600FSA). Many of the photos on this page are of a prototype mount and prototype ATS Portable Pier. The photos do not include this recommended adapter. |
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Easy to Adjust and Polar Align. Precise polar alignment can be achieved easily using the precision adjusters for both altitude and azimuth. The system locks down with zero alignment shift for an unprecedented ability to achieve that "perfect dead-on" polar alignment that is so critical to the best imaging and the most accurate go-to slews. |
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Transportable ATS also makes permanent piers for the 3600GTO that can be fitted with the same flat top plate. Please see the ATS website for details on their permanent piers. |
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Precise Mechanical Fabrication
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Highly accurate mechanics. Our machinists are among the most skilled available anywhere, attending to the smallest detail to ensure a precision instrument. The finishing department assures that all parts are deburred, sanded, polished and painted to provide an exceptional aesthetic appearance. Our mount assembly is directed by a life-long astronomer with more than 20 years of experience here at Astro-Physics! All of our production personnel take great pride in their work and are true craftsmen and women. |
Worm gear accuracy.
Critical worm gear accuracy
is maintained by special machining techniques developed
at Astro-Physics after extensive studies, actual
field operation and many years of experience making precision mounts. Our
worm accuracies are second to none and are guaranteed to be 5 arc seconds
(+-2.5 arc sec.) or less, peak-to-peak. The periodic error of each mount
is verified during our intensive testing procedures prior to optimization
as described below.
Pre-programmed with PEMPro
Periodic error corrections for each individual mount
are optimized during extensive testing, which results in excellent performance
right out of the box. 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. We optimize performance further by characterizing the
error using a special version of PEMProAP and downloading the appropriate
correction into the mount's GTOCP3 before it leaves Astro-Physics. Simply
use the Keypad or PulseGuide software to turn PE Correction "on," and you will
see results that are even better than our published 5 arc second spec!
With additional PEMPro runs, you can achieve even higher levels of accuracy.
If your application requires the highest possible levels of tracking accuracy, you may want to consider the Precision Encoder System described below.
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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 0.044 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, removable |
| 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 | ~ 0.4 to 0.8 amps at 15 volts - tracking ~ 1.5 to 3.0 amps at 15 volts - both motors slewing at top speed of 600x |
| Power requirements | Nominal 15 volt DC supply at 10 amps recommended |
| Periodic error | +/- 2.5 arc seconds or less in one worm cycle (5.6 minutes); native, prior to any error correction |
| Maximum slew speed | 2.5 degrees / second |
Servo Motor Drive
The drive system uses a high-torque precision Swiss DC servo motor in each axis controlled by a microprocessor in the GTOCP3 control box. The encoders on these motors provide a resolution of 0.05 arc seconds per step for incredible pointing accuracy. Tracking is very smooth, noticeably smoother than any stepper motor drive or inexpensive servo drive. The system can be accurately controlled over a speed range of 4800:1 which allows 0.25x sidereal for manual guiding to roughly 720x sidereal for 3 degrees per second maximum slew rate. The circuit draws well under an amp when tracking the stars, 3 to 5 amps with both axes slewing and requires only 12 volts to operate (15-18 volts is recommended). This servo drive will satisfy the requirements of the sophisticated, advanced astrophotographer, yet is easy for the casual, visual observer to use.
The GTOCP3 Control Box contains all of the circuitry to drive the servo motors and the logic required to navigate the sky. It can be easily removed from the mount, if required. The GTO Keypad is a self-contained computer that serves as the communication center for the operation of your GTO mount. 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. Please refer to GTOCP3 Control Box and Keypad for Servo Drive for more detailed information.
All of our electronics are now lead-free. Astro-Physics believes that we who love the night sky should also love and protect our good earth.
For reliable operation in your observatory, we recommend that you use a minimum 10 amp filtered, regulated power supply like our 15V, 12-amp power supply (PS15V12AC). For lighter, well-balanced loads, you can use a commonly available heavy-duty, deep-cycle marine 12V battery.Flexible Control with either Keypad or Personal Computer
Keypad OperationPlease note that the Precision Encoder System is only included when you order the 3600GTOPE version of the mount. It is not included in the standard version (3600GTO) and cannot be retrofit at a later date.
A precision encoder installed in
the RA axis provides feedback to the servo to eliminate periodic error
to a level below 1/2 arc second for long-period exposures. This
feedback system eliminates periodic error by monitoring the actual output
speed of the RA axis using this encoder ring to continuously adjust the
speed of the servo motor, which keeps the axis rotating at a very precise
and constant rate. The operation of the encoder does not interfere with
any external guiding, centering or slewing commands sent by the keypad,
CCD camera or external software. Its only function is to keep the axis
tracking precisely at the sidereal rate, and will also follow any variable
rate that is programmed into the servo for purposes of countering atmospheric
refraction and other sources of drift. PulseGuide™ Software Please note: Ray Gralak, the author
of PulseGuide, is currently working on a new software program, Astro-Physics
Command Center, that will include all the
features of PulseGuide, plus additional features. The new software will replace
PulseGuide when it becomes available. In the meantime, here's the information
on the existing PulseGuide software: PulseGuide is a stand-alone Windows (98, ME, 2000, NT4,
XP, Vista and Windows 7) utility that provides complete remote control
of Astro-Physics Mach1GTO, 400GTO,
600EGTO,
900GTO,
1200GTO, 1600GTO 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.
More .... PEMPro v. 2.0 Software - FULL Version! Optional Accessories To Enhance the Performance of Your Mount This stainless steel counterweight was designed to fit onto the 2.5" diameter shaft of the 3600GTO. It features a spring-loaded, recessed lock knob and measures 7.9" in diameter by 2.5" thick.
22" Dovetail
Saddle Plate (DOVE3622), 22" Dovetail Sliding Bar (SB3622, no longer available) and 27" Dovetail
Sliding Bar (SB3627) for the 3600GTO
The massive and sturdy two-part telescope mounting system provides the convenience of a dovetail with the security of a fixed mounting plate. It was designed for strength, rigidity and versatility. The dovetail system can be set up for tip-in or slide-in of the dovetail sliding bar. Safety slots on the saddle plate coupled with the sliding bar's safety stop will help keep accidents from happening.
27" Dovetail Sliding Bar (SB3627) 16.5" Dovetail Plate for PlaneWave (DOVEPW)
In order to accommodate the wide PlaneWave Instruments dovetail
plate offered with their CDK17, CDK20 and CDK24 telescopes, Astro-Physics has
designed a new 16.5" Dovetail Saddle Plate. This plate features four clamps
and can be used with the Astro-Physics 3600GTO, 1600GTO and 1200GTO Mounts. Click here for additional
information. Flat Surface Adapter for the 3600GTO (3600FSA)
We strongly recommend the use of a flat
top-plate and our 3600 Flat Surface Adapter when designing your setup
for the 3600GTO mount, whether on a portable or a permanent pier. Bolt
this adapter onto the flat plate at the top of your pier. Bolt circle:
This 2.5" diameter extension is beautifully machined from the same 303 stainless stock as the full counterweight shaft of the 3600GTO and adds another 10" of usable length. The fit of the extension on the primary counterweight shaft is virtually seamless, so your weights will slide up and down smoothly. The large machined counterweight safety stop knob threads into the end to protect your toes. The shaft weighs 13.5 lb. (6.1 kg) Current Installations Support All Astro-Physics mounts are supported by a dedicated staff who will assist with any issues that may arise. You can talk to a real person in a timely manner. Astro-Physics staff also participate in the ap-gto user groups in the Yahoogroups forum. The user group is comprised of GTO owners who are willing to share their wealth of experience using their mounts as well as imaging strategies and other concerns of advanced amateurs. We have prepared some pertinent support documents, including
the 2008/2009
manual relating to this mount and many of our other products
on our Technical Support page. You may find the information that you need
simply by clicking
here. Price and Delivery Information
The 3600GTO and 3600GTOPE are not available at this time and we do not have any
production planned.
Test results on the new 3600 mount with optional feedback encoder
have exceeded all our expectations. The measured tracking error was well below
1/2 arc second for a 20 minute time period. With this option, it is now practical
to do long period unguided imaging with a fixed setup where other sources of
drift (due to polar misalignment, tube flexure, etc) have been minimized or
eliminated.
Astro-Physics pioneered the use of precision encoders, normally used in the
machine tool industry, to help you achieve optimal results during unguided or
guided astrophotography. The 9" stainless steel Renishaw encoder that we have chosen is dimensionally stable and has guaranteed subarc second resolution over a 24 hour cycle. It is precisely aligned with the corresponding Renishaw Read-Head and tested. This is not a simple tape encoder, which cannot guarantee precise alignment and can shrink with temperature.
The system has been under test since late 2007 and we invite you to review our document entitled: Precision Encoder for the 3600GTO. We have anticipated the questions you may have, i.e. What does the encoder do? How does the encoder do this? and have provided these answers for your review.
To further refine the unguided error of the mount, we are adding an all-sky tracking rate to the software, which will minimize RA drift everywhere in the sky. This will allow significant unguided exposure times with a well polar-aligned mount.
PEMPro (Periodic Error Management
Professional) is a Windows software application developed by Ray Gralak that
makes it easy to characterize and reduce periodic error.
While the periodic error of your 3600GTO has already been optimized with a special
version of PEMProAP to be well under 5 arc seconds (+-2.5 arc sec.)
or less, you can reduce it even further to maximize performance without auto-guiding.
PEMPro v. 2.0 is the latest version of PEMPro and
includes exciting new features like the "Polar Alignment Wizard" to
quickly, accurately and easily dial in your polar alignment. The software will
be included with all new 3600GTO mounts. More
...
Optional switches can be installed to control operation past the meridian and for homing. The Limit/Homing Switch System can be used as a simple electronic switch or can be used in conjunction with software to establish limits. All mounts will be drilled and tapped to accept this option, which can be added as an upgrade later and installed by the customer. Please refer to the document entitled: Limit/Homing Switch for the 3600GTO for a discussion of these options.
If you have also purchased the 3600GTOPE that has the precision encoder. You
will also need to purchase 3600GTO Cable to Connect Limit Switch Connector on
Cable Port Plate to GTOELS (CAB36LS) below.
3600GTO Cable to Connect
Limit Switch Connector on Cable Port Plate to GTOELS (CAB36LS)
This cable is needed if you plan to control your Limit Switches with the GTOELS
Control Box.
30 lb. (13.6 kg) Counterweight for the 3600GTO (30SCWT)
For permanent installations, a series of matching through-holes in the saddle
and tapped holes in the sliding dovetail plate allow the setup to be bolted into
its final position through both plates once adequate balance is achieved. As
an added feature, the saddle plate has two cable-routing channels on the eyepiece
end, each 2" wide and approximately 0.5" high. These channels allow you to access
the large opening at the top of the
dec axis to run your cables through the mount. Refer to the cabling section of the manual (for the mounts shipped in 2008/2009) to see how easy this is.
The dovetail plate is drilled on the underside of the eyepiece end so that you can attach a plate that can be customized as a cabling port. The photo on the right shows a blank plate attached.
22" Dovetail Saddle Plate (DOVE3622) The DOVE3622 saddle plate (shown in the photo to the right) is a female
dovetail and features four spring-loaded clamps that will grip the largest instrument
solidly. It can be attached to the mount in three possible positions - centered,
forward or back depending on the balance point of your instruments.
HISTORICAL REFERENCE ONLY: 22" Dovetail
Plate (SB3622, no longer available) This robust male plate features a myriad of holes throughout
the entire length that can accommodate a variety of instrument configurations
at various balance points. This plate can accommodate instruments
that have hole spacings of 3.2" (Astro-Physics hole pattern), 3.5", 5.5" and
7.45". These holes extend from one end of the
plate to the other allowing you to space rings as you wish. You can also use
two (or even three, depending on instrument size) 16" Dovetail
Plates (DOVELM162, new style introduced February 17, 2009) in a side-by-side
configuration for multiple instruments. The DOVELM162 is drilled to
attach directly onto the SB3622. The DOVELM162 also features lock-down knobs
that can be firmly tightened with an allen wrench.
27" Dovetail Plate (SB3627) This plate is similar to the SB3622, however
the additional 5" of length make it a great choice for extra-long instruments
or side-by-side configurations. Our own experience mounting our prototype 305mm
f3.8 Riccardi-Honders and 305mm f12.5" Maksutov-Cassegrain pointed out
the need for a longer plate. Hole spacings include: 3.2"-3.5" slot, 3.937",
4.5",
4.921" 5.5", 6.875", 7.450"and 8.220" to accommodate an even wider variety
of instruments. They are repeated throughout the length of the plate. Suitable
instruments include: All rings with the Astro-Physics hole pattern, 305mm f3.8
Riccardi-Honders, and large Takahashi instruments. The DOVELM162 can
be bolted on for side-by-side configurations as mentioned above.
22" Dovetail Saddle Plate for the 3600GTO (DOVE3622)
12.9" x 22" (328 x 559 mm), 15 lb. (7 kg)
9.9" x 27" (251 x 686 mm), 13 lb. (6 kg)
Please review the Hole Pattern Chart.
The 3600GTO fits into the ID of the adapter; eight side bolts hold the mount
in place. This adapter is machined from a solid plate and is ribbed in the
base for strength and reduced weight. It is 12" OD, 1 7/8" tall
and weighs 5.75 lb.
11.5" Counterweight Shaft Extension for the 3600GTO (M3655)
3600GTO Shipping Crates, set of two
These crates are required for shipping the 3600GTO. One crate will contain the
declination axis and the other will contain the RA axis and polar fork assembly.
3600GTO - What's Included?
3600GTOPE (with the Precision Encoder) - What's Included?
Items that You Will Need for Your Mount
Refer to the information above for these items or links provided:
Optional Items
Refer to the information above for these items:
Additional Recommended Accessories
Copyright © 1999-2022, Astro-Physics,
Inc. - All Rights Reserved
This page was last modified:
July 6, 2022
Astro-Physics, Inc.
11250 Forest Hills Road, Machesney Park, IL 61115, U.S.A.
Phone: 815-282-1513 Fax: 815-282-9847