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Review: A Year with the Explore Scientific / Losmandy G-11 with PMC-Eight

Review: A Year with the Explore Scientific / Losmandy G-11 with PMC-Eight

Steve Siedentop

I've had the PMC-Eight for a little over a year.  There were some growing pains early on, but I'm very happy with the mount and its performance.  I've spent a good bit of time imaging with the PMC-Eight G-11 and have laid out my thoughts below.

Steve Siedentop with his Explore Scientific ED127 Air-Spaced Triplet and the Explore Scientific/Losmandy G11 with PMC-Eight

General Build

It’s a Losmandy G-11, so it’s solid and the workmanship is consistent and superb.  The Explore Scientific PMC-Eight incarnation is no different and includes the RA Extension option which allows the mount to be used with the largest telescopes sold by Explore Scientific. 

The mount comes with a high precision worm gear but does not come with the one-piece worm block.  The two-piece worm block wasn’t a problem until I adjusted the mount and found that working with the two-piece worm block is a bit of a challenge.  The process is well documented on multiple websites, but rather than learn the process, I opted to upgrade to the one-piece worm block on each axis and found the adjustment process to be easy and simple. 

The G-11 is often described as a "bargain premium mount." The build quality and the precision of the individual components are on par with premium mounts and performance is excellent.  The controller itself is probably a bit over-engineered but is rock solid. The aluminum case has a clean look to it and mounts easily on the tripod leg. 

If 3-D printing is your thing, there are a number of files to download from the site and print your own mods, including cable management gadgets, tablet/smartphone brackets,  and an improved mounting bracket for the controller.


The PMC-Eight controller requires 12 volts and uses the generally accepted standard 2.1mm x 5.5 mm plug.  The stepper motors are quiet and smooth.  After the most recent firmware upgrade, my mount pulls .75 amps when tracking and 1 amp when slewing.  In contrast, my CGEM DX consumed 1.5 amps when tracking and 2.5 amps when slewing.  
Growing Pains

The Explore Stars app is solid and does exactly what they say it will do. The UI is a bit less than intuitive in some places, but overall, it’s easy to use. The iPad version installs flawlessly.  Some users have reported issues with the installation process of the Android version.  I definitely prefer using the iPad version of Explore Stars over the Android and Windows versions, but that's very likely my own personal bias as an Apple user. 

The mount did not come with the spring washer on the RA axis. This was a $10.00 purchase from Losmandy and took about 2 minutes to install. There was a discussion between ES and Losmandy on whether or not the mounts should come with this spring washer, but I'm not aware of the outcome.  This "wavy washer" makes the RA axis much less stiff and easier to balance, but isn't necessary. 

There were a few points of contention that I had regarding what should be, in my opinion, "core functionality." As an example, switching between the serial port and the WiFi connection was well documented by ES but the process was quite a bit more technical than I felt it should have been. Fortunately, the PMC-Eight is an open-source project and there are user-contributed applications that perform such maintenance functions with the click of a button.
Open Source Community

I attended the PMC-Eight User Conference in 2018 and really enjoyed meeting the people at Explore Scientific and touring the facilities.  I also enjoyed being able to discuss the future of the product with the designers and hope they hold another one in the future.  Out of the PMC-Eight User conference in 2018 came a realization that the ES folks did not have a full understanding of the open-source concept. Fortunately, they were very receptive to our input and out of that came the PMC Eight Steering Committee to drive the PMC-Eight open source project.

ASCOM Driver code is available for anyone to view. The SDK contains good examples and is available for download to folks who want to write their own PMC-Eight utilities and applications. ES migrated from Yahoo Groups to Groups.IO.  You’ll find lots of good info, along with the good, the bad, and the ugly. I personally appreciate the transparency and accessibility of the ES folks as that's something you don't generally see from a manufacturer in our space.  

There are two ways to control the PMC-Eight. The first is through the ExploreStars app, available for Windows, Android, and iOS.  As I noted earlier, I definitely prefer the iPad version and it performs flawlessly. The app connects over WiFi and works well. For visual use, a spot-on polar alignment is not necessary, as the app dynamically points/tracks on both axes to compensate for drift due to a less than accurate polar alignment. I don't recommend the app for scope control while imaging.

The second way to connect is via the ASCOM driver for Windows or the INDI driver for your favorite Linux distro, which can connect over WiFi or via the PMC-Eight controller's serial port.  The driver is not written as a server, so you'll need to use POTH for multiple connections to the mount if you're guiding via ASCOM. Refactoring the driver as a server is something that is actively being worked on. Because this is an open-source project, anyone in the community can take it upon themselves to refactor the driver as well. There is also an INDI driver for the mount if you're a Stellarmate/KStars/Astroberry fan.

The EQMod ASCOMPad driver works well with the PMC-Eight and your favorite game controller if you are interested in having a physical controller.  Note for those using the PMC-Eight for the first time:  You can use either the Explore Stars app on a tablet or the ASCOM/INDI driver on a Windows/Linux device.  You can't use both.  If imaging is your thing, stick with the ASCOM or INDI driver.


The level of support for this product is what I've come to expect from Explore Scientific. The ES folks are engaged and accessible on Groups.IO and respond quickly to questions and issues. Explore Scientific is the only company I've found that has provided this level of accessibility and transparency.

GoTo Performance

GoTos with the Explore Stars app are as good as you would expect from a modern goto mount. I had no problem centering objects on a 20 mm 70 degree eyepiece in an f/8 refractor. ASCOM gotos through Cartes du Ciel (or your favorite scope control application) are as spot-on as you would expect provided you have a good physical polar alignment starting out. You'll find on the Groups.IO page that folks are also using The Sky X, Stellarium, SkySafari (with WifiScope), Cartes du Ciel, and AstroTelescope (Mac application that uses INDI).


Tracking is what I expected from a mount in this class. Quite a few users have posted PHD guide logs on the Groups.IO website for reference.  Keep in mind that this information is subjective based on the experience level of the user.  I have quite a bit of imaging time under my belt and I’ve been able to guide at .1 to .2 arcseconds on nights with good seeing.  That’s more than enough for round stars with my imaging rig which is an Explore Scientific ED127CF FCD100 with their .7 Reducer, a cooled DSLR, and a 60 mm guide scope with an Orion SSAG.


Eighteen months ago, I would have told someone who was interested in getting started with imaging to look for a more mature product that had been out for a while. I'm to the point now where I'm happy to recommend the mount. The support is top-notch, the system is well designed and transparent, and the community is maturing as a great support resource in addition to the competent and responsive support folks at Explore Scientific.

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