iOptron CEM120 Go-To 120 lb. Payload Center-Balanced Equatorial Mount Head with WiFi
Part Number: 7300
For imagers and observatories that demand more—more capacity, more precision, more modern control—the iOptron CEM120 stands ready. Designed around iOptron’s signature “center balance” concept, the CEM120 takes what amateur astronomers loved about the smaller CEM mounts and scales it to serious professional-grade capacity, while still remaining approachable enough to install in a permanent backyard setup.
With a weight capacity of 115 pounds (52 kg), not including counterweights, the CEM120 is built for larger optical tube assemblies, dual-scope configurations, and imaging rigs that include filter wheels, large format cameras, and guide scopes. But raw strength means nothing without stability, and that’s where the “center balanced” design shines. By aligning the weight of the mount and payload directly over the center of the pier or tripod, the CEM120 avoids the torque and imbalance that can degrade tracking performance in more traditional GEMs. The result is smooth, steady operation—even when fully loaded.
This stability supports exceptional tracking precision. The CEM120 features a high-grade stepper motor system paired with a zero-backlash worm drive and steel RA and DEC axles. Each worm wheel is 216mm in diameter with 360 precision-machined teeth, and the native periodic error is impressively low—measured at less than ±3.5 arcseconds. That’s not just adequate for astrophotography, it’s exceptional—and even more so when paired with the mount’s built-in Permanent Periodic Error Correction (PPEC), allowing you to refine and retain tracking performance over time.
The mount’s onboard electronics offer a suite of modern conveniences for remote and robotic operation. Wi-Fi and LAN connectivity come standard, giving you flexible control options whether you’re imaging from across the observatory or across the country. A 32-channel GPS receiver automatically configures your time and location. An internal cable management system is thoughtfully designed to reduce cable strain and prevent tangles—essential when your imaging train includes multiple power and data lines.
You’ll also find iOptron’s Go2Nova 8407 V2 hand controller included. It features the company’s Advanced GOTONOVA GoTo system and a built-in heater for cold-weather operation, plus a deep celestial object database spanning Messier, NGC, IC, UGC, and other popular catalogs. Precision polar alignment is made easier with large fine-thread azimuth and altitude adjusters. And for guiding, the mount includes a dedicated ST-4 autoguider port, as well as multiple USB and serial ports to support a variety of guiding and imaging software.
Mechanically, the mount is built to last. The all-metal body is CNC-machined, with large 80mm diameter steel RA and DEC axles and 125mm bearings to absorb the stresses of continuous tracking and slewing. The counterweight shaft is stainless steel, anti-slip, and measures 38.1mm in diameter—wide enough to hold multiple weights without flexure. The included saddle is a long-format 17.2" (437mm) Losmandy-style D plate, ready to handle large OTAs or dual-mount setups with confidence.
Although it comes standard as a mount head only, the CEM120 pairs easily with a wide variety of piers and observatory-grade tripod bases. A 10 kg (22 lb) counterweight is included, and iOptron is offering a second one free for a limited time, giving you extra flexibility for heavier loads.
What’s in the Box
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CEM120 mount head
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Go2Nova 8407 V2 hand controller with heater
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Stainless steel counterweight shaft
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10 kg (22 lb) counterweight (plus a bonus counterweight for a limited time)
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Hand controller connection cable
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Serial cable (#8412)
Note: pier or tripod is sold separately.
Technical Highlights
The CEM120 offers a slew of engineering advancements that support its high-precision performance. The 240-second worm period ensures gentle, smooth motion across the sky. The RA and DEC axles are 80mm in diameter and ride on oversized 125mm bearings for long-term durability. Both worm wheels are 216mm in diameter and include 360 finely cut teeth for smooth gear engagement. Tracking resolution is 0.07 arcseconds per step, and the mount can slew at speeds up to 4° per second—ideal for rapid target acquisition.
With a power draw of just 0.7 amps while tracking (and 1.8 amps during full-speed slewing), the CEM120 is also relatively efficient given its size. It operates on 12V DC at 5 amps, which makes it compatible with most power supplies used in permanent and mobile setups alike.
For advanced users, cable routing is a particular standout. The CEM120 includes 2 USB 2.0 ports, 3 USB 3.0 ports, 2 DC 12V outputs (1A), 2 higher-current 5A DC ports, ST-4 port, auxiliary ports, and a dedicated USB for polar scope connection. This flexibility allows for complex, tidy cable routing through the mount itself—ideal for observatories where you want to minimize cable movement and the risk of snagging.
Observing Tip
If you operate in a location where Polaris is obstructed—common in roll-off roof observatories or installations with high southern horizons—the optional iOptron iPolar electronic polar scope is a worthwhile upgrade. It provides a digital polar alignment routine that doesn’t require visual access to the North Star, making it far easier to achieve accurate alignment in compromised conditions. While not required, it’s one of those small upgrades that can save you time every night.
Final Thoughts
With the CEM120, iOptron has delivered a mount that stands comfortably in the observatory-grade class—but without the jaw-dropping price tag normally associated with this level of capacity and performance. It brings together exceptional engineering, innovative design, and future-proof connectivity in a platform that’s equally at home under a backyard dome or in a remote robotic site. If you’re building the imaging rig of your dreams, this is the mount you can count on to carry it—tonight and every clear night that follows.
