GM4000 HPS Mount Details


 

 

 


 

 HPS 


 

HPS (High Precision and Speed) is the total system integration of special high resolution absolute encoders with the sophisticated QCI control system and 10Micron's precision worm drive mechanics, delivering <1arcsec p-p precision and high speed (20deg/sec), at a price previously unachievable by any other technology.  With the integration of 10Micron's new HPS System into the GM4000HPS, advanced amateurs and professionals now have the ultimate observatory platform to use for acquiring long exposure unguided images with very large instruments.  The high-resolution absolute encoders are permanently attached and calibrated to each axis, not simply as an add-on to an existing system, but fully integrated mechanically and electrically into the control system.  The HPS encoders know their absolute position, even after power down.  Factory inspection and calibration of each mounting ensures that the phenomenal accuracy is maintained throughout the full rotation of each axis.

 

HPS Tracking Curve (obtained from a GM2000HPS)

 

Drive System Comparisons

 

When selecting a mount and considering different drive systems, it is important to consider the tradeoffs associated with each approach.  Traditional motor- encoded precision worm gear driven mountings have predominated the amateur market for many years, providing good value and accuracy (typically ~8 arcsec p-p).  Open-Loop Periodic Error Correction can reduce this by almost a factor of two in the best situations.  However, the accuracy of even the best mountings still falls short and requires autoguiding or very short exposures to prevent trailing. 

 

Recently, a new Direct-Drive system has arrived on the amateur mounting market.  These systems incorporate high resolution encoders on each axis and directly drive their axis' without the use of gears (the axis itself becomes the motor, requiring high currents to provide sufficient torque to drive and hold position).  While this approach has some advantages, in practice, it also has disadvantages to overcome.

 

We think the hybrid 10Micron HPS System provides the best overall solution, providing extreme accuracy and speed, along with the portability, quick setup, reliability, and robustness of a conventional worm driven mounting.

 

If you are comparing mounts and their drive systems, we suggest you click on the link below for an overview of the different drive types and their tradeoffs:

 

 


 Capability 


 

 

Flexible Control

No separate computer needed, even in remote automated installations. The GM4000HPS incorporates a full featured and flexible GoTo control system that provides both total standalone operation as well as full remote operation of all mount functions.  The integrated control system utilizes a powerful AMD microprocessor and is housed in an on-board fan cooled enclosure.  Its internal LINUX based software is fully upgradeable and future-proof, avoiding the constraints and limitations common with hardware based controllers.  QCI provides a large suite of object databases for powerful and convenient location of objects and is as easy to use for casual use as it is for serious work.  The full function handpad incorporates an industrial wide-temperature capable red backlit display and illuminated keypad to provide reliable access to all functions through a convenient menu and button interface. 

 

Notable functions include accurate polar alignment routines and a sophisticated internal pointing model that utilizes up to 25 stars to achieve pointing accuracies of under 15".  Full featured and robust software interfaces include support for LX200 protocol (same as Meade 16’’GPS), AP GTO protocol, and ASCOM (via LX200). QCI also includes a full suite of hardware interfaces for remote automated operation - including integrated LAN for remote connection without a PC!  For more details on this powerful integrated control system, please click on this QCI Control System link.

 


Home Sensing

In order to provide rapid unattended error recovery, the GM4000 has been equipped with precision homing sensors in both Dec and RA axes.  In the event of power loss or other unforeseen occurrences, the system can be quickly and accurately re-calibrated by performing a home command.   Software slew limits allow restriction to prevent collisions with observatory structures, and internal mechanical stops prevent inadvertent over travel and cord-wrap.


 

Cable Management

The amount if instrumentation needed in many applications places large demands on the amount of cabling required.  As a result, robust and reliable cable management becomes a critical aspect of any observatory mounting.  The GM4000 has been designed to enable the cleanest cable routing possible - through the mount itself.  The Dec and RA axis include large 60mm (2.4") diameter pass-through openings which will allow routing of cables with large connectors.


No-Clutch Design

Even the best mount and drive systems exhibit sub arc-minute (repeatable) pointing errors.  These small errors can be compensated for by software pointing models (such as Tpoint, or the built-in multi star alignment modeling of the QCI + HPS control system).  In order to provide software pointing accuracy at this demanding level, it is necessary to maintain the relationship of the drive gears and the mount axes.  In the case of a mount with clutches (like the GM2000HPS), it is possible to change this relationship by manually moving the mount and causing the clutches to slip.  The choice to add clutches has many benefits for portable use.  The GM4000HPS foregoes the use of clutches, in order to enable the very highest level of software pointing accuracy.   In case of encountering fixed objects (observatory roof, pier, etc), the QCI control system is designed to limit the amount of force applied by the motors, in order to minimize any damage to equipment.

 

Both RA and Dec worms of the GM4000HPS are user disengage-able to facilitate balancing of instruments. 

 


Accessories

10Micron offers a full selection of useful adapters and accessories for the GM4000HPS.  For more information on Accessories, please click this link.

 


 Professional Capacity and Performance  


 

Capacity

Mount capacity is often misunderstood, and many manufacturers imply this to simply be a function of gear size.  While most mountings (even small ones) can physically support and drive very large loads without failure, capacity is determined first and foremost by the rigidity of a mounting.  Rigidity is simply the 'springiness' that is felt when pressing on the telescope or against its focuser.  It is quite easy to judge the rigidity of a mounting simply by pressing against the telescope's focuser in each direction, and noting how much a star shifts in the eyepiece for a given force.   Professional applications demand the ability to handle large instrument loads with minimal mounting deflection in order to maximize the inherent pointing accuracy of the system and reduce sensitivity to wind and other externally induced forces/vibrations.  While software pointing routines are able to compensate for repeatable deformations, only through minimizing the mount's inherent flexure can total errors be reduced and  superior accuracy achieved.

 

Unfortunately, it is not really possible to simply compare mountings on the basis of gear size, physical size, weight, or appearance.   Many unseen elements are primary contributors to a mount's performance.  The primary elements that contribute to rigidity (capacity) are the stiffness of the two axes and their bearing support system, the stiffness of the drive system (torsion/twist) and the rigidity of the supporting structure of the mount itself (of course, rigidity of the permanent pier is an additional significant factor).  Like a system of springs, the rigidity of a mount is the result of all these factors combined, and is often limited by its weakest element.  Therefore, it is important to understand the key elements that go into a mount's design and fabrication.

 

Axis:  An often hidden or overlooked aspect of good mount design is the design and construction of the RA and Dec axes.  Much of the flex felt in commercial mountings is due to inadequate axis stiffness.   This can be caused by poor bearing configuration, long cantilevering of the axis, or inferior construction and materials.  Even some seemingly large and impressive looking mountings suffer from surprisingly soft axes due to poor design and execution. 

 

The nature of fork mountings places large loads on the RA axis.   The stiffness of the fork itself is a significant weak link in this type of mounting, requiring significantly more structure and mass to reduce the flexure.  For this reason, it is very difficult for any fork mount to achieve the rigidity and pointing accuracy of a german equatorial.  In order to achieve comparable performance, an equivalent fork mount can require several times the mass and cost.

 

The GM4000 utilizes massive 85mm (3.4") diameter thick-wall steel for the RA axis and 80mm (3.2") for the Dec axis.  Steel is 3 times stiffer than aluminum (which is often chosen for its lower weight).  Both axes are supported by extra-large diameter (130mm) preloaded conical tapered roller bearings, which give much greater stiffness and bearing capacity than ball bearings.  The primary loads have been carefully designed to be closely coupled to the bearings.   The result is an extremely high axis stiffness that minimizes flex in all directions.

 

Structural:  The key structural elements of the GM4000 (RA and DEC housings, Altitude Support Plates) and their attachments have been structurally engineered for rigidity.  These key parts are precision machined as single pieces from solid bar or plate stock, in order to deliver the highest rigidity and accuracy possible.  The altitude support plates are machined from 38mm (1.5") solid plate and are rigidly coupled to the oversized 185mm (7.25") diameter RA housing through precisely mating surfaces and 6-point clamping.   In order to provide the absolute maximum rigidity and minimize vibration and flexure, all critical structural parts have been left in their solid state with NO internal pocketing.  This avoids the structural weakening that occurs in all mounts that utilize pocketing to reduce weight for portable use.

 

Drive System: An often overlooked aspect of mount design is the structural performance of the worm drive.  Simply going to larger worm wheel sizes can not fully make up for a weak worm drive.  All torsional (twisting) loads placed on the axes of a worm-driven telescope mounting must be reacted through the worm itself.  The size and configuration of the worm bearings and the worm mounting play an important role in determining torsional rigidity.  The GM4000 worm support structure has been designed to minimize flexure of the bearing mounts as well as the anti-backlash pivot.  The 32mm diameter steel worm is mounted with oversized precision tapered conical worm bearings which transmit the worm thrust loads with less axial flex than ball bearings.  These aspects combine to make the drive system of the GM4000 torsionally stiff and capable of handling physically large instruments without excessive flexure and vibration.

 

 

The end result of all this careful engineering and execution is a professional mount that exceeds expectations for rigidity and capacity. 

 

 

 


Performance

Drive System 

The GM4000HPS makes use of new technology brushless AC Servomotors to deliver high torque and accuracy, along with long life and freedom from motor brush maintenance.   These motors incorporate a new approach in servomotor design - F.I.S.   The Fully Integrated Servomotors incorporate the critical drive control and encoder electronics into the motors themselves.  This enables the unique mix of performance and high accuracy inherent in the GM4000HPS drive system.

 

The spring loaded anti-backlash mechanism of the GM4000HPS worm drive delivers near zero backlash at the telescope.  A unique zero-cogging kevlar belt final reduction drive results in whisper quiet operation with virtually zero motor backlash.  Gone are the grinding and whirring noises of the all-gear drives used in most other telescope mountings.  Onlookers at NEAF 2007 were often seen pressing their ears close to the mountings just to see if they could hear the motors running. 

 

No professional mount would be complete without a highly accurate and reliable drive system.  Automated mountings demand a difficult mix of high speed and high accuracy - over a long life of night-after-night use in automated installations.   To meet these tough demands, 10Micron engineers chose the ideal material pairing of a special gear Bronze for the worm wheel , and a carefully matched alloy steel for the worm (not stainless steel, which has inferior properties for use in a worm).  While these materials add significant cost compared to the aluminum gears found on many commercial mounts, the superior friction and long wear properties of the GM4000 gears are critical to delivering the high speed, smoothness, and low error over the life of the mounting.

 

The bronze worm wheel and hardened steel worm are produced using the latest state-of-the-art tooling and machinery.  Worms are evaluated using precision helical path analyzers to ensure a consistent and smooth low periodic error.  After assembly, each mounting is analyzed as a complete system using even higher precision encoders to ensure the HPS tracking accuracy meets the 10Micron standards.

 

 


 Precision and Finish  


 

Precision

The GM4000 was developed at 10Micron by a team of professional engineers with decades of experience in the design and in-house production of  astronomical telescope mountings as well as precision turnkey machinery for the machine tool industry in Europe.  Each mounting is fully machined, inspected, and assembled in-house at 10Micron's production facility in Italy.  As machining and tooling experts, 10Micron is able to consistently produce a level of precision that is unique in astronomical mountings. 

 

In order to deliver the absolute highest accuracy and rigidity, with perfect consistency mount-to-mount, all critical parts of the mounting are machined as single pieces from solid plate or bar stock.  No welded, screwed-together, or crude cast structures are used.  The quality of machining and fabrication is evident in every part of the mounting, inside and out.  Part-to-part fit and matching is superb and machined edges are fully radiused and blended for a functional and aesthetically pleasing look. 

 

 

Fit and Finish

The fit and finish of every part is given close scrutiny.  Just like its smaller sibling, all external surfaces of the GM4000 are hand finished through a time consuming buffing process to eliminate tooling marks, swirls, and sharp edges.  This process results in an exquisite satin finish that gives a beautiful and consistent look part-to-part, and serves to hide any smudges or marks that inevitably result from normal use.

 

After surface finishing, the complete set of GM4000 parts are anodized together in one batch, in order to provide high consistency of color part-to-part.  The hardness of the anodized surface resists wear and chipping, unlike paint.  The end result of all this careful finishing is a mounting that is as impressive to look at as it is in operation. 

 

Colors

The GM4000 is available in attractive metallic Gray.

 

Last Update 08/24/13

 

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