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LOSMANDY GM-8 AND G-11 GERMAN EQUATORIAL MOUNTS
While the GM-8 remains very popular, the G-11 mount is a particularly attractive choice for those who require a high degree of performance and reliability. And who find it inconvenient to obtain repair assistance at remote locations since the G-11 mount among the few high performance platforms whose components are modular, symmetrical, and fairly simple to service or replace in the field. Our experience is that there is rarely a need to return a head to the USA for service more so since Company Seven technicians put in about four to five man hours checking through and fine tuning each new G-11 which we receive. You are not likely to encounter any defect that would require a return of the head sold by Company Seven for service.
Payload ratings of telescope mounts vary with design and material used, and in the manner with which the proud manufacturer judges their product, and so this alone is not a reliable predictor of performance. A telescope mount has several factors that will affect suitability including: static load, length and torque, desired tracking accuracy, tripod or pier resonances, etc. What is most important to the user of the product is how rigidly the mount holds the payload, how smoothly it tracks (amplitude and smoothness of the periodic error of a gear), and how it overcomes the moment imparted by the load. This will vary with weight of the load, and the physical length of the load. The weight put onto the mount can vary depending how the instrument is to be used; for example one telescope used for visual work only may be as much as fifty percent lighter in weight than another employed for imaging (possibly with guide scopes, cameras, etc.). The potential loading on the mount may also vary with local winds; even a slight wind on the "sail" area of a large reflecting telescope can dramatically increase the effective load imparted to the mount. So, a small mount operating from within a shelter (such as a dome) with a short and narrow telescope might perform as well or better than a larger mount outside a sheltered environment. Indeed, some people elect to buy a smaller mount and then put the balance saved by not buying a larger mount into a shelter.
Read Company Seven's Review of the original Losmandy G-11 Mount with Celestron C-11 telescope. This was a revolutionary departure from the previous traditional fork mounted arrangements being the first large SCT optical tube assembly sold mated to a German Equatorial platform. The CG-11 became the most successful mid aperture Schmidt Cassegrain telescope system ever sold by Company Seven.
Common Features of both GM-8 and G-11 Mounts:
- All machined mountings made from stainless steel and aluminum barstock
- Hollow R.A. axis with detachable polar scope for quick, accurate
alignment in the field
- Removable precision ground 1.25" diameter stainless steel
counterweight shaft
- Fine altitude and azimuth adjustments for quickly and accurately
zeroing in on the Celestial pole in the field
- Setting circles with Porter Slip Ring Design; polar-axis ring is
driven; it follows the stars without needing to be reset each time
you look at a new object
- Both axes machined to accept optional high-resolution encoders for
use with popular digital setting circles
- Customer's choice of control electronics:
- Model 492 Dual Axis Drive Corrector, or
- Losmandy Gemini Computer Controlled "Go-to" System
Right: Losmandy Model G-11 German Equtorial Mount Head shown without furnished tripod, counterweight shaft.
Clutch adjustment handles shown are optional. Click on image to see enlarged view.
| SPECIFICATIONS OF G-11 MOUNT SYSTEM* |
| R.A. Gear Wheel: |
5.625", 360 tooth 7075 T35 aluminum |
| DEC. Gear Wheel: |
5.625", 360 tooth 7075 T35 aluminum |
| DEC. and R.A. Worm gear: |
440C Stainless (54 Rockwell hardness) |
| Worm gear support: |
Dual supported ball bearings |
| Worm gear coupling: |
Oldham |
| Laser Engraved Setting Circles: |
Porter Slip Ring design, 5" DEC. and R.A., |
| Right ascension resolution: |
4 minute increments, pointer |
| Declination circle resolution: |
1 degree increments, pointer |
| R.A. Axis Needle Thrust Bearings: |
one 3.75", one 2", and two 1.625" |
| DEC. Axis Needle Thrust Bearings: |
one 3.75", one 2", and two 1.625" |
| DEC. and R.A. Clutches: |
Slip clutch, variable friction, one knob ea. axis |
| Latitude Tangent Arm range: |
12 to 64 degrees with polar scope, 8 to 68 with minor modification |
| Azimuth adjustment range: |
+-8.5 degrees |
| Dovetail Saddle Plate: |
"D" Series Standard |
| Weight of Mount Head |
Approximately 31 lbs. |
| Weight of Field Tripod |
approximately 20 lbs. |
| Semi-Pier Tripod Height |
34 to 48 inch |
| Load Capacity: |
Approximately 60 lbs. |
G-11 Instruction Manuals
-
 "Losmandy™ Model G-11 Instruction Manual". Complete 12 page instruction manual as furnished with our Losmandy Model G-11 German Equatorial Mount. Publication content by Losmandy Hollywood General Machining, all rights reserved. From Company Seven's Library. 180,349 bytes (in Acrobat Reader ".pdf" format).
- "Losmandy Pole Finder Instructions" Illustrated instruction manual as written by David A. Kodama for Losmandy, with slight reformatting by Company Seven. This document covers the older Losmandy reticle (with the errant pattern), as well as the current model. Furthermore, it provides assistance for our Southern Hemisphere neighbors. Provided in support of customers who buy the optional Losmandy German Equatorial Mount Pole Finder.
| SPECIFICATIONS OF MODEL 492 DIGITAL DUAL AXIS ELECTRONICS* |
| Power Requirements:
| 12 Volt D.C., 500 MA* |
| R.A. and DEC. Geared Motors: |
SAIA 48mm Stepper Drive Motors |
| Motor MTBF: |
2.5 years of continuous operation |
| Hand Control: |
Diamond Pattern Push Botton Switches, DEC. &
R.A. Reversing, |
| Quartz Tracking Rates: |
Sidereal, Lunar, Solar, King |
| Fine Movement Rates: |
4x, 8x, 16x Sidereal |
| Photo-Guide Setting Rates: |
+-30%, 50%, and 2x Sidereal |
| R.A. Drive Gear Correction: |
user programmable Periodic Error Control |
| DEC. Drive Backlash Correction: |
user programmable Time Variable Correction |
| North/South Hemisphere Operation |
selectable by user |
| Miscellaneous: |
Compatible with our SBIG CCD Star Tracker & Imaging CCD Systems such as our ST series including the original Model ST-4 |
* Power Source Notes we suggest the user consider one of the following options:
- operate from wall current (with GFCI outlet) with an AC/DC inverter. Ideally this should be through a Line Conditioner/Surge Suppresssor (contact us to discuss what we offer).
- If you intend to use a 12 VDC power supply then please ensure that it is noise free, and regulated to +/- 5%. It must have a current supply of at least 2.5 amps with no appreciable voltage drop. Be especially careful when using an instrument with running vehicles as a supply source since a malfunctioning alternator or voltage regulator as well as vehicle power demands, can produce power surges and appreciable amounts of AC power which can easily damage the micro controller in your instrument.
- For simple observing, use a portable rechargeable 12 Amp hour (or greater capacity) 12 Volt D.C. rechargeable battery pack.
- For higher current demands use a sealed, Deep Cycle/Marine/R.V. battery. These are readily available at automotive service and parts centers. This does not have to be the most immense battery, one designed for a golf cart for example may be adequate for your needs.
Right: Losmandy Model GM-8 German Equtorial Mount Head shown without furnished tripod, counterweight shaft.
Click on image to see an enlarged view.
| SPECIFICATIONS OF GM-8 MOUNT* |
| R.A. Gear Wheel: |
2.8", 180 tooth 7075 T35 aluminum |
| DEC. Gear Wheel: |
2.8", 180 tooth 7075 T35 aluminum |
| DEC. and R.A. Worm gear: |
440C Stainless (54 Rockwell hardness) |
| Worm gear support: |
Dual supported ball bearings |
| Worm gear coupling: |
Oldham |
| Laser Engraved Setting Circles: |
Porter Slip Ring design, 3.5" DEC. and R.A., |
| Right ascension resolution: |
6-minute increments, pointer |
| Declination circle resolution: |
2 degree increments, pointer |
| R.A. Axis Thrust Bearings: |
one 2.1", one 2"; two 1.5" needle |
| DEC. Axis Needle Thrust Bearings: |
one 2.1", one 2"; two 1.5" needle |
| DEC. and R.A. Clutches: |
Slip clutch, variable friction, one knob ea. axis |
| Latitude Tangent Arm range: |
0-64 degrees with polar scope, lower latitude wedge available |
| Azimuth adjustment range: |
+-8.5 degrees |
| Dovetail Saddle Plate: |
Optional "C" or "D" Series |
| Weight of Mount Head |
Approximately 17 lbs. |
| Weight of Field Tripod |
Approximately 15 lbs. |
| Semi-Pier Tripod Height |
36" to 48" |
| Load Capacity: |
Approximately 30 lbs. |
| GM-8 MOUNT TYPICAL SHIPPING ARRANGEMENT* |
| Head Box Dimension |
20 x 15 x 15 inches / 50 x 38 x 38 cm |
| Head Box Weight |
43 lbs. / 19.6 kg |
| Tripod Box Dimension |
33 x 12 x 13 inches / 84 x 31 x 33 cm |
| Head Box Weight |
19 lbs. / 8.6 kg |
| Standard Counterweight |
8 x 8 x 4 inches / 20 x 20 x 10 cm |
| Head Box Weight |
9 lbs. / 4.1 kg |
* Specifications subject to change.
GM-8 Instruction Manuals
- "Losmandy™ Model GM-8 Instruction Manual". Complete 12 page instruction manual as furnished with our Losmandy Model GM-8 German Equatorial Mount. Publication content by Losmandy Hollywood General Machining, all rights reserved. From Company Seven's Library. 180,304 bytes (in Acrobat Reader ".pdf" format).
- "Losmandy Pole Finder Instructions" Illustrated instruction manual as written by David A. Kodama for Losmandy, with slight reformatting by Company Seven. This document covers the older Losmandy reticle (with the errant pattern), as well as the current model. Furthermore, it provides assistance for our Southern Hemisphere neighbors. Provided in support of customers who buy the optional Losmandy German Equatorial Mount Pole Finder.
POPULAR AVAILABLE OPTIONS FOR THESE MOUNTS
Accessories Section for illustrations and descriptions
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Right: Losmandy Model G-11 German Equtorial Mount Head shown without furnished tripod, counterweight shaft.
