iOptron CEM40 Center Balanced GoTo Equatorial Mount With iPolar, 1.75" LiteRoc Tripod, and Case
Part Number: C402A3
A Portable Workhorse That Thinks Like a Premium Observatory Mount
The iOptron CEM40 is one of those rare equatorial mounts that manages to hit a sweet spot—merging high-end features and serious payload capacity into a compact, travel-ready package. Whether you're a visual observer looking to support a large refractor or a dedicated astrophotographer aiming for sub-arcsecond tracking, the CEM40 gives you the tools to do the job with a minimum of fuss and a maximum of confidence.
Weighing just 15.8 pounds, the CNC-machined CEM40 head supports a 40-pound payload, not including counterweights. That’s a 2.5:1 payload-to-weight ratio—one of the best in its class—meaning you can mount everything from an 8" RC to a fully loaded imaging train without pushing the mechanics to their limit. The secret to its stability lies in iOptron's patented Center-Balanced Equatorial Mount (CEM) design. By placing the center of gravity directly over the tripod or pier, the mount minimizes torque, balances more naturally, and reduces stress on the motors and gears. The result is smoother tracking, faster balancing, and a setup that simply feels more stable in the field.
Built-In iPolar™ for Fast, Accurate Alignment—Even When You Can’t See Polaris
One of the standout features of the CEM40 is its integrated iPolar™ electronic polar alignment system. Permanently mounted in the RA axis and aligned at the factory, iPolar uses plate solving and a built-in camera to calculate your true celestial pole alignment in real time—even when Polaris is blocked by trees, buildings, or heavy light pollution. You no longer need to strain your neck, guess at reticle patterns, or waste time on iterative alignment routines. Just launch the software, follow a simple on-screen guide, and you’ll be polar aligned in minutes with a level of precision that visual polar scopes simply can’t match.
Engineered for Performance: Stepper Motors, Zero Backlash Worm Gears, and iOptron’s Proven Electronics
Inside the CEM40’s anodized red-and-black housing, iOptron has installed precision stepper motors paired with zero-backlash 216-tooth worm gears on both axes. Each axis rides on oversized 68mm bearings with 45mm steel axles, allowing the mount to move smoothly under load with virtually no play. With a standard periodic error of ±7 arcseconds, the CEM40 is well-suited for long-exposure astrophotography right out of the box, and it includes Permanent Periodic Error Correction (PPEC) to further refine its native tracking.
If you need even more precision, the CEM40's high-end sibling, the CEM40EC, includes real-time encoder-based PEC for performance under 0.25 arcseconds RMS. But even the standard CEM40 gives you excellent results when paired with an autoguider, and its integrated ST-4 guiding port and USB connectivity make it easy to plug into your existing imaging workflow.
The mount’s maximum slew speed is a quick 4.5° per second, and its Go2Nova® 8407+ hand controller gives you full access to an onboard database of more than 359,000 celestial objects—including Messier, NGC, IC, UGC, MCG, and Caldwell catalogs. Star identification, custom user objects, and easy firmware upgrades are all standard. The controller includes a built-in dew heater to prevent LCD fogging in cold environments.
Travel-Friendly by Design—with Practical Touches for Field Use
For all its performance, the CEM40 was clearly designed by people who understand what it means to haul equipment to dark skies. The mount head includes a custom-fitted hard case to protect it from bumps during travel or storage, and the included 1.75" LiteRoc tripod offers excellent stability at a low weight. The LiteRoc’s stainless steel legs lock securely and reduce vibration transfer, while remaining light enough to carry short distances fully assembled.
Another thoughtful feature: the CEM40 includes iOptron’s Universal Self-Centering Saddle (USCS). This patent-pending dovetail clamp can accept both Vixen-style and Losmandy-style plates—without needing adapters or tools. Just drop in your OTA and secure it with the large hand knobs. The saddle automatically centers and grips the plate securely, making setup faster and more foolproof.
A 32-channel GPS receiver is integrated into the mount head for automatic time, date, and location input, and the CEM40 can be optionally upgraded with Wi-Fi control using iOptron’s external Wi-Fi module, allowing wireless operation via tablet or smartphone with apps like SkySafari or iOptron Commander.
Observing Tip
The CEM40’s center-balanced design isn’t just marketing fluff—it makes a genuine difference when balancing asymmetrical loads like imaging rigs with off-axis guiders, filter wheels, and large cameras. Traditional German equatorials often need counterweights moved far down the shaft to achieve balance with such setups, adding unnecessary strain and vibration. The CEM40, by contrast, naturally minimizes torque and handles these loads with greater stability and smoother tracking, especially in wind-prone conditions.
If you image with a refractor and a large full-frame camera, you’ll appreciate the finesse of this design every time you calibrate autoguiding or shoot long subs.
Final Thoughts
The iOptron CEM40 is a mount built for real-world astronomy—not just impressive specs on paper. It travels light, sets up fast, aligns precisely, and delivers the kind of tracking performance you'd expect from mounts twice its weight. Whether you're imaging from your backyard observatory or deep in the field, it offers a feature set that punches far above its price point.
This is the kind of mount your telescope will thank you for.
