Mechanics
The Losmandy GM8 is a venerable German equatorial mount renowned for its reliability, durability, and exceptional build quality. Constructed solely from stainless steel and anodized aluminum, it exudes strength and longevity without the use of any plastic components. The mount boasts a payload capacity of approximately 35 pounds for visual use and 25 pounds for astrophotography. We’ll delve into these specifications in more detail later. Additionally, the GM8 can be disassembled into multiple components for easy transportation or reconfigured with parts from the Losmandy G11 to create the hybrid GM811 mount. This illustrates the GM8’s inherent modularity, allowing for a range of upgrades and modifications as new technologies and enhancements become available.
One of the features of the GM8 is its use of a Vixen V/Losmandy D style hybrid dovetail saddle, which enables it to accommodate either style of dovetail as well as CGE plates, which are similar in size to D series plates. However, it’s important to note that older GM8 models may only have a Losmandy dovetail saddle, which won’t accept Vixen plates; you’ll need to buy a new saddle to fit telescopes with these.
Interestingly, the Losmandy GM8 is equipped with the same 1.25-inch diameter shaft as the larger Losmandy G11. This choice might seem unusual for a mount of this size, and it certainly looks a little silly on such a small mount. While the 1.25-inch diameter counterweights function well, this dimension implies that you cannot use the smaller diameter counterweights common in many existing mounts, and vice versa. Consequently, if you own telescopes requiring heavier counterweights, you’ll need to purchase additional 1.25-inch bore counterweights even if you already possess suitable counterweights with a smaller diameter. This can be seen as an unnecessary and costly aspect of using the GM8. A single 7 lb weight is supplied with the mount; for almost any purpose, you’ll need to grab another; Losmandy offers 7 lb, 11 lb, and 21 lb counterweights for 1.25” shafts.
The GM8, like the G11 and an increasing number of new mounts, uses slip-ring clutches to clamp the mount in place, avoiding issues with inaccuracy or wear buildup over time on the right ascension or declination axis. The GM8 does not come with a polar scope as a standard feature, but it does have a polar axis housing that is compatible with Losmandy’s polar scope or a PoleMaster. One of these alignment tools is virtually essential for achieving accurate polar alignment, which is critical for anything beyond casual visual use.
Included with the GM8 is a folding aluminum tripod, the “Folding LW Tripod”, which resembles more of a portable pier than a traditional tripod and is similar to the Losmandy G11’s tripod but much lighter. If you’re upgrading your GM8 to a GM811, it’s advisable to also upgrade the tripod to the G11 version for enhanced stability and support.
The GM8’s “Folding LW” tripod offers adjustable height ranging from 27 to 43 inches and weighs a mere 15 pounds. This is considerably lighter than the G11’s tripod/portable pier, which weighs closer to 44 pounds. The GM8 mount head itself weighs just 21 pounds, bringing the total weight of a fully assembled GM8 to an impressively light 36 pounds. To put this in perspective, the Sky-Watcher EQ5 Pro, a mount with a similar payload capacity, weighs around 34 pounds when fully assembled, even though it uses far smaller (and thus lighter) gears and motors than the GM8, among other things.
One of the main advantages that the Losmandy GM8 holds over its competitors, especially those manufactured in China, lies in its lower periodic error and superior drive and guiding accuracy. However, the GM8’s smaller diameter drive gear on the right ascension axis somewhat limits its potential in comparison to the larger drive gear utilized in the Losmandy G11. For those seeking enhanced performance, upgrading to the GM811 hybrid mount or opting for the G11 outright alleviates this limitation. In its stock configuration, the right ascension drive of the GM8 is best described as average rather than outstanding, primarily due to the smaller drive gear. A well-tuned EQ6R or HEQ5 might beat it in accuracy with small payloads. Nevertheless, the GM8 generally exhibits fewer errors compared to more affordable mounts, and there is typically less adjustment required right out of the box.
Electronics
The modern Losmandy GM8 comes standard with the Gemini 2 GoTo system. The Gemini 2 system is composed of a hand controller and a control box securely attached to the mount, which in turn connects to the mount’s drive motors and encoders. Notably, the Gemini 2 boasts a touchscreen with various buttons, and the main control box offers connectivity options such as Wi-Fi adapters or a direct connection to a PC for extended operational choices. Additionally, a GPS adapter can be integrated, although the required information can also be obtained through a smartphone or a Wi-Fi/PC connection. The mount and Gemini 2 can run off DC or AC power.
It is important to note that older versions of the GM8 were equipped with simpler motors without encoders and featured a basic dual-axis drive with a hand controller that provided various tracking and pointing adjustment options. While this setup is adequate for planetary imaging or visual observation, it falls short for astrophotography. Upgrading an older GM8 to meet contemporary astrophotography standards, by incorporating the tucked motor kit and the Gemini 2 system, is essential for compatibility with modern software. However, this is not a trivial expense, and one should carefully consider the cost-benefit ratio, especially when contemplating the purchase of a used GM8. The subsequent section, titled “Should I Buy a Used GM8?” delves further into the details and considerations for upgrading an older GM8.
The GM8 employs servo motors, which are of exceptionally high quality. However, one of the challenges with the GM8’s total tracking/guiding accuracy is its smaller right ascension drive axis in comparison to the G11 and GM811, which boast larger diameters with more gear teeth, allowing for finer control. In practical terms, the tracking and guiding accuracy of the GM8 might not significantly outperform that of a more robust but less premium tier mount like the Sky-Watcher EQ6-R, assuming equivalent payloads, or a “hyper tuned” equivalent sized mount. However, the GM8 is remarkably well-constructed and offers greater portability than many of these options.
There are several add-ons available for the Gemini 2, such as a GPS module for updating the computer’s date, time, and location information. However, a smartphone can already supply this necessary information. Moreover, by incorporating a Wi-Fi adapter and connecting it to the Gemini 2 control box, you can control the mount via an app like SkySafari wirelessly, with automatic updates to the date, time, and location via your smartphone’s internal clock and GPS.
Using the Losmandy GM8 for Visual Observation
Setting up the GM8 for visual use is relatively straightforward. After leveling the tripod, assembling the telescope/counterweights and performing a polar alignment, the Gemini 2 controller will prompt you to align on at least one object, and you’re good to go. More objects (i.e., stars or planets) can be added to the computer’s model to improve accuracy, but this may not be necessary.
Losmandy does not explicitly publish a weight capacity rating for visual astronomy concerning the GM8. However, it is worth noting that the stated astrophotography weight limits of 30 to 40 pounds for the GM8 are actually more in line with what is appropriate for visual observation. Consequently, the GM8 can adequately support an 8 to 10-inch Schmidt-Cassegrain, an 8-inch Newtonian, or a 6-inch refractor for visual purposes.
While the GM8 can technically accommodate a 10-inch Newtonian or an 11-inch Schmidt-Cassegrain, it’s not advisable to push the mount to these extremes. Even the larger, hybrid GM811 can feel somewhat strained with telescopes of this magnitude. If you are considering using larger telescopes, it would be prudent to upgrade to the full G11 mount to ensure stability and performance.
Another important aspect to consider is the length of the telescope tube. For example, an 8-inch Newtonian with a longer tube will be significantly less stable on the GM8 compared to an 8-inch Schmidt-Cassegrain, which has a more compact and stubby tube. This difference in tube length can impact the balance and stability of the entire setup on the mount.
A well-matched optical tube for the GM8 would be the Celestron C9.25 XLT telescope. When fully equipped, this telescope weighs approximately 25 pounds and is an excellent pairing with the GM8 for visual observation or planetary imaging. It is believed that the GM8 was partially designed with this telescope in mind, along with the Celestron C8. Conversely, mounting a C11 on the GM8 can be highly unstable and is not recommended due to safety concerns.
A 10-inch Schmidt-Cassegrain, while it may feel top-heavy and wobbly, can still function adequately on the GM8. The same goes for other stubby designs, such as classical Cassegrains up to 10” and ~30-35 lb. However, large Newtonians pose a particular challenge on the GM8, primarily due to the lightweight tripod typically provided with the mount. With a Newtonian, the combination of the telescope and mount becomes top-heavy, which can make the setup unstable, especially in windy conditions.
Astrophotography
Losmandy cites an astrophotography weight capacity for the GM8 in the range of 30 to 40 pounds, depending on the length of the telescope tube. However, these numbers should be taken with a grain of salt, or better yet, rejected as outright insane. Realistically, the far bigger and heftier G11 might be able to handle 40 pounds for astrophotography under optimal conditions with a short tube. The GM8, however, struggles to support even 35 pounds for visual observation. It is rather perplexing as to why these numbers are quoted in such a manner. A common rule of thumb for astrophotography is to take the manufacturer’s stated maximum weight capacity and divide it by a factor of 2/3 to 1/3, depending on how conservative the estimate is, which would be about 15-25 pounds in the case of the GM8, though 20 lbs is a more conservative figure.
Consequently, the GM8 is ideally suited for medium to small-sized astrophotography telescopes. For Newtonian telescopes, it can handle sizes up to 6 to 8 inches. For Schmidt-Cassegrain telescopes, the maximum size is around 8 inches, and for refractors, 110-120mm.
When it comes to astrophotography, it is absolutely critical to achieve a razor-sharp polar alignment with any equatorial mount, such as the GM8. There are a plethora of methods at one’s disposal to attain this, which encompass the implementation of software-based techniques for polar alignment such as drift alignment, or harnessing the capabilities of specialized hardware like a polar scope (offered by Losmandy as an aftermarket addon) or the QHY PoleMaster. It is critically important to be scrupulous in ensuring that the telescope is assembled with precision and is perfectly balanced on the GM8. This is a cornerstone procedure for any equatorial mount, and its importance is heightened for imaging purposes owing to the rigorous precision required.
The GM8 can be seamlessly autoguided by interfacing it with a PC through its ST4 port, allowing the user to wield control of pointing the mount with the electronics that are included and merely utilize a PC for managing an autoguider. However, an increasing majority of astrophotographers have a preference for dedicated, automated imaging software that has integrated controls for the mount. These sophisticated software suites are replete with advanced features such as plate solving, which bestows upon the user the ability to locate celestial objects with unerring accuracy, and imaging sequences that streamline and automate the processes of capturing images, slewing, and orchestrating meridian flips. In addition, the guiding, which is inherently reliant on software and a PC, can be automated by a majority of these software packages and run commands directly to the mount rather than through the issue-prone ST4 port. The GM8 can be operated in this manner by plugging in a correct cable to the Gemini II system and your PC or with an aftermarket WiFi adapter – though if you don’t have the Gemini II kit installed, the GM8 is not compatible with either option.
Should I buy a Used Losmandy GM8?
An aged GM8 might lack some of the electronic features found in more modern models, but the majority of its components are probably similar or capable of being upgraded. Losmandy takes pride in providing spare parts and servicing for all GM8 mounts, no matter the history of ownership. The GM8 is often regarded as one of the premier choices for buying second-hand, owing to the exceptional quality of its components, the relative simplicity of interchanging these components, and the consistently superb customer support provided by Losmandy, which extends to buyers of pre-owned mounts. When upgrading a used GM8, it is advisable to ensure that it incorporates the latest features, such as the Tucked Motor Kit and the Gemini 2 system, especially if the primary use case is astrophotography. However, if the mount is intended for visual observation, these upgrades might not be as critical, though some investment may still be necessary to tailor the mount to specific requirements.
Over the years, the GM8 has seen its share of enhancements, particularly with respect to the Gemini GoTo system. Notable among these upgrades is the inclusion of ‘Tucked Motors,” which are an essential component for compatibility with the Gemini 2 GoTo system. It’s noteworthy that the Gemini 2 system itself incorporates new motors, which adds to the overall cost.
Furthermore, the GM8 can be equipped with two different types of supporting portable piers. One of these is the currently-supplied lightweight variant, while the other is a heavy-duty version, akin to what is offered with the G11. The heavy duty pier/tripod is substantially steadier, and is a must if you have any aspirations to convert to a GM811. Moreover, a polar scope is a necessary accessory, and it is worth noting that older models may not be compatible with Vixen dovetails unless a hybrid Vixen/Losmandy dovetail saddle upgrade is added.
Additionally, the pricing dynamics can be intriguing. In certain scenarios, a used G11, given the same set of accessories and add-ons, might be more cost-effective than a GM8. On the other hand, a used GM811 could be an alternative worth considering.
Alternative Recommendations
The Losmandy GM8 is, in many ways, considered a successor to the Vixen Great Polaris, which was an enhanced version of the Super Polaris. The Super Polaris, offered by Vixen in the 1980s, often had Celestron telescopes attached to it. Eventually, the Super Polaris evolved into the Great Polaris, which was not as extensively marketed in the United States as its predecessor. For a variety of reasons during the late 1990s, several Chinese companies, including Synta, which is now a leading manufacturer in the industry, attempted to clone the Super/Great Polaris to compete with Vixen and Losmandy in the premium German equatorial mount market. To some degree, they were successful, as the GM8 has significantly lost market share, and you’ll commonly hear about the Celestron Advanced VX, the latest and seemingly the last in line to the dynasty of Super Polaris successors, in astronomy circles.
The early 2000s witnessed the development of the Synta/Celestron CG-5 mount, alongside the parallel development of Meade’s equatorial mounts. These mounts bear some resemblance to the Losmandy GM8, though they are often lighter. The Celestron CG-5 began as a manual mount with a dual-axis drive, similar to the basic package offered by the Losmandy GM8, and later evolved into a fully computerized GoTo mount, initially as the CG-5 ASGT and finally as the Advanced VX. Interestingly, the CG5 and Advanced VX were essentially developed by trying to replicate the exact metal castings used in the Vixen Polaris mounts, a lineage that is quite visible in the design. Additionally, the Sky-Watcher HEQ5 Pro mount, which is manufactured by the same plant as the CG5/Advanced VX and sold by various brands, including Orion, was developed as a clean sheet design. This mount boasts stepper motors and a superior mechanical configuration.
In the early 2000s, Meade released the LXD55, which was not very well-received, and later evolved into the slightly better but still subpar LXD75. The LXD75 could have been comparable to the CG5 if it weren’t for its less sturdy extruded aluminum tripod, which is inadequate for handling heavier loads. The LXD75 is still sold today – re-badged as the Bresser EXOS-2. It eventually evolved into the unsuccessful LX80 and now the LX85, which is very similar to the Advanced VX, albeit with different paint and a less efficient hand controller.
Besides the CG5, Advanced VX, HEQ5 Pro/Sirius, and Meade LX series, there are several other mounts that can be compared to the Losmandy GM8 and, by extension, the Super/Great Polaris. These include the Meade LX70, which is a manual mount that may still be available new, and the Sky-Watcher EQM-35 Pro, which is considerably smaller than the Losmandy G11 but comes equipped with GoTo and tracking capabilities.
The Orion Sirius and its identical counterpart, the Sky-Watcher HEQ5 Pro, could theoretically support a 9.25-inch Schmidt-Cassegrain telescope and are mechanically comparable to the Advanced VX and LX85. However, these mounts usually come with smaller tripods with 1.75-inch diameter legs instead of the sturdier 2-inch legs, which compromises their stability to some extent. They can be fitted with larger format tripods to address this issue. This is similar to the Bresser Exos-2 GT, although its interface and performance are generally not highly recommended.
However, it’s important to note that the GM8 does not compare to more robust mounts like the Celestron CGEM, Orion Atlas EQ-G, Sky-Watcher NEQ6, or their more recent counterparts, the CGEM II, EQ6Ri Pro, and AZ-EQ6. These Synta-made mounts are more comparable to the Losmandy G11 or the GM811 hybrid mount in terms of payload capacity and total weight/heft.
For individuals new to astronomy or astrophotography, understanding the nuances of different mounts can be overwhelming. It is worth mentioning that not everyone needs a mount as substantial as the GM8, especially if you’re using smaller telescopes or camera lenses. For those interested in astrophotography with lighter setups, exploring star trackers might be a more suitable and cost-effective alternative.
For those specifically geared towards deep-sky astrophotography, it is highly advisable to consider a larger mount than the GM8, such as the GM811 or G11 – even if you’re just starting out in the hobby. Although this might seem like an added expense initially, it’s an investment that could save costs in the long run. As your experience grows, you may find yourself wanting to upgrade your telescope or add more equipment to your setup. Opting for a mount with a higher payload capacity from the outset will allow you the flexibility to expand your setup without the need for another mount upgrade – be it a new Schmidt-Cassegrain OTA or changes to an imaging setup.
Aftermarket Accessory Recommendations
To effectively use the Losmandy GM8 or any equatorial telescope mount, a polar alignment tool is essential. You have the option of either using Losmandy’s own polar scope or a third-party tool like the PoleMaster polar alignment adapter. While it is technically possible to rely solely on software for polar alignment, it is not advisable, especially with the GM8, as it does not include the extensive software suite that mounts from other manufacturers such as Orion, Sky-Watcher, and Celestron usually come bundled with.
In addition to a polar alignment tool, you will need an appropriate power supply for the GM8. The Celestron PowerTank Lithium is a popular option, but generic equivalents are also available.
Finally, for enhanced control and convenience, consider adding a Wi-Fi adapter to your GM8 setup. This is a valuable addition, irrespective of your specific astronomical pursuits, as it allows for wireless control and communication with the mount.
