iOptron CEM120 EC2 Center Balanced EQ Mount With Dual High Precision Encoders

iOptron CEM120EC2 GoTo German Equatorial Mount with Dual Encoders – 115 lb Payload Capacity, Sub-Arcsecond Tracking, and Observatory-Class Precision

The flagship of iOptron’s mount lineup, built for serious observatories, research-grade astrophotography, and remote automation.

When you’re ready to go beyond visual observing and basic imaging—and build a system capable of research-grade tracking accuracy, dual-axis modeling, and observatory-level payload handling—the iOptron CEM120EC2 is the mount that meets the moment.

This is not a starter mount. It’s a precision-engineered, center-balanced equatorial mount with the performance, capacity, and connectivity required for permanent installations and automated observatories. Designed for demanding astro-imagers, university observatories, and advanced visual astronomers, the CEM120EC2 delivers extraordinary tracking precision, expanded automation options, and a best-in-class load-to-weight ratio.

Key Benefits and Features – In Depth

What makes the CEM120EC2 stand apart isn’t just its raw specifications—it’s the way iOptron integrates technology, mechanical refinement, and usability into a mount that performs far beyond its size and price. From the dual encoders to the advanced control options, every element has been designed for astronomers who need a robust, observatory-grade platform.

At its core, the CEM120EC2 utilizes iOptron’s patented center-balanced architecture, a mechanical design that aligns the telescope's center of mass directly over the tripod or pier. This dramatically increases stability while reducing the total amount of counterweight required to balance the load. That translates into smoother slewing, less stress on the gear system, and a higher payload capacity in a lighter overall package. With a true payload rating of 115 lbs (52 kg) and a head weight of only 57 lbs (26 kg), this mount offers one of the best load-to-weight ratios in the industry.

What sets the EC2 apart from other models in the CEM120 family is its dual high-resolution encoders—one on each axis. Unlike mounts that rely on a single encoder or that apply periodic error correction from stored PEC curves, the CEM120EC2 uses real-time positional feedback on both RA and DEC axes, actively correcting for tracking errors as they occur. This allows the mount to achieve remarkable sub-arcsecond tracking accuracy—less than 0.15 arcseconds RMS under optimal conditions—without requiring autoguiding. Combined with Real-Time Periodic Error Correction (RPEC), this ensures consistent tracking even with long focal length instruments, and makes it ideal for unguided imaging, high-precision photometry, and automated survey work.

iOptron also equips the CEM120EC2 with a host of modern connectivity and automation features. A built-in 32-channel GPS automatically sets your location and time for accurate GoTo operation, and the included Go2Nova 8407 V2 hand controller provides intuitive navigation with a 359,000+ object database. For fully remote control and observatory integration, the mount offers Wi-Fi, LAN, USB, and RS-232 communication ports, ensuring compatibility with popular control systems like ASCOM, INDI, NINA, TheSkyX, and ACP. The hand controller even includes a heated LCD display to maintain visibility in cold conditions—a thoughtful touch for winter observing.

Cable management is another standout feature. Rather than requiring you to thread power and data cables around a rotating mount head, the CEM120EC2 includes an integrated cable management system with powered USB 2.0 and 3.0 ports, 12V and 5V DC outputs, and dedicated ports for guiding, accessories, and auxiliary control—all routed internally. This not only reduces setup time and clutter, it also helps eliminate cable drag and accidental disconnections during tracking or slewing—especially important for robotic imaging runs or overnight unattended sessions.

Mounting your optical tube securely is handled by a 17.2" Losmandy-style saddle, which is both spring-loaded and independently adjustable. This long saddle helps distribute weight more evenly, especially on longer OTAs or multi-instrument rigs. Precision worm gears (216mm diameter, 360 teeth) in both axes, matched with 80mm steel shafts and 125mm bearings, provide mechanical smoothness and long-term durability, even under heavy loads.

Finally, the CEM120EC2 includes a thoughtful package of accessories to get you started immediately. You’ll receive the mount head, hand controller and cables, a stainless steel counterweight shaft, and not one but two 22-pound (10 kg) counterweights—the second provided as a limited-time bonus. A range of piers and tripods, including the Tri-Pier 360 and permanent steel pier, are available to match your preferred installation style.

Technical Specifications Summary:

Observing Tip:

The CEM120EC2 excels in remote automation and multi-night imaging campaigns. If you use software like NINA, ACP, or TheSkyX, the mount’s LAN/Wi-Fi capabilities and precision model retention make it ideal for scripted, unattended astrophotography. This mount is also excellent for mosaic work, allowing accurate framing across multiple sessions without realignment.

Final Thoughts:

The iOptron CEM120EC2 is more than just a telescope mount—it’s an imaging platform. Designed for payloads that push well beyond standard mounts, it supports long refractors, big astrographs, and multi-instrument payloads with ease. From its dual high-resolution encoders to its thoughtful cable management, it’s a system built for flawless performance and rock-solid reliability. If you’re ready to invest in a mount that can carry your vision forward—whether that’s deep-sky imaging, research, or public outreach—the EC2 stands ready.