iOptron CEM40 Center Balanced GoTo Equatorial Mount with 1.75" LiteRoc Tripod
Part Number: C401A3
Precision Performance in a Lightweight, Field-Ready Package
The iOptron CEM40 is a highly portable, center-balanced equatorial mount designed for visual observers and astrophotographers who want high capacity and serious performance without the bulk of a traditional German equatorial. This mount head weighs only 15.8 pounds, but thanks to iOptron’s patented Center-Balanced Equatorial Mount (CEM) design, it can support telescopes and imaging rigs weighing up to 40 pounds—more than 2.5 times its own weight.
Whether you’re setting up a permanently mounted scope in your backyard or packing your rig for a remote dark-sky trip, the CEM40 offers a rare combination of mechanical refinement, high-tech features, and smart ergonomics that make setup, alignment, and tracking not just easier—but more accurate, too.
This version of the CEM40 includes the standard 1.75-inch LiteRoc tripod, offering excellent stability and reduced vibration in a compact, lighter-weight form. A custom hard case for the mount head is not included with this configuration, but is available separately for those looking to upgrade their field protection.
The Center-Balanced Advantage
Most mounts struggle when loaded near their weight limit—but the CEM40 handles heavier OTAs and accessories with ease, thanks to its center-balanced design. Instead of offsetting the RA axis like traditional GEMs, the CEM places the center of mass directly over the tripod or pier. This improves load distribution, reduces flexure and torque, and results in smoother tracking with fewer vibrations.
The RA and DEC axes are machined from solid steel and supported by oversized 68mm ball bearings for added stiffness under load. Both axes use zero-backlash 216-tooth worm wheels for precise motion control, and the entire body is CNC-machined from anodized aluminum for durability and thermal stability in the field.
The 17mm worm gears and stepper motors drive the mount with a native periodic error of ±7 arcseconds (typical), and Permanent Periodic Error Correction (PPEC) is included to improve guiding accuracy over time. For those needing even tighter tracking (like sub-arcsecond RMS), the upgraded CEM40EC version includes a high-resolution encoder on the RA axis for real-time PEC correction down to <0.25 arcsec RMS.
iPolar™ Electronic Polar Alignment Made Easy
Every CEM40 comes standard with iOptron's iPolar electronic polar scope, permanently aligned and integrated into the RA axis. Unlike traditional polar scopes that require visual access to Polaris, iPolar uses a sensitive internal camera and advanced plate-solving software to calculate your true celestial pole alignment—even if Polaris is completely blocked by buildings, trees, or clouds.
This makes alignment faster and far more precise than using manual methods, especially in urban or obstructed environments. Just connect the mount to your computer via USB, open the iPolar software, and follow the on-screen prompts. You’ll be polar aligned in just minutes—with a level of accuracy that improves your tracking and GoTo performance right from the start.
Go2Nova® Control and Quiet, Precise Slewing
The CEM40 is driven by iOptron's ultra-quiet precision stepper motors, which offer low power draw and excellent positional control. Combined with 128 microsteps per full step, the motors allow for smooth slews, silent sidereal tracking, and accurate autoguiding. The motors support a maximum slew rate of 4.5° per second, meaning you can hop across the sky quickly when needed—or track fine targets with surgical accuracy.
The included Go2Nova® 8407+ hand controller provides access to one of the largest object databases available, with over 359,000 celestial objects including Messier, NGC, IC, UGC, MCG, and even user-defined objects. The controller is equipped with a built-in dew heater to prevent fogging during cold observing sessions, and it includes tools for custom tours, star identification, and automatic GoTo alignment routines.
Smart Features for the Field
iOptron thoughtfully integrated a variety of features to make the CEM40 field-friendly:
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A 32-channel GPS module is built into the mount head, automatically setting your date, time, and location for fast GoTo alignment and accurate tracking without needing to consult your smartphone.
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The mount includes an ST-4 autoguider port, a USB communication port, and DC power outputs, all integrated into the internal cable management system to reduce the risk of tangles and snags as your scope slews.
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The patent-pending Universal Self-Centering Saddle (USCS) accepts both Vixen and Losmandy-style dovetails without tools or adapters. The saddle centers the dovetail automatically and grips securely—just drop it in and lock it down.
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Although Wi-Fi isn’t built in, the CEM40 can be controlled wirelessly using an optional external Wi-Fi module, letting you run your mount from SkySafari, iOptron Commander, or other apps.
Technical Specifications
Mount Type: Center-balanced German Equatorial (CEM)
Payload Capacity: 40 lbs (18 kg), excluding counterweights
Mount Head Weight: 15.8 lbs (7.2 kg)
Payload-to-Weight Ratio: 2.5
Material: CNC-machined aluminum, steel axles
Exterior Finish: Red/black anodized
Latitude Range: 0° to 60° (special shaft for <10°)
Azimuth Adjustment: ±6°
RA/DEC Worm Wheels: Ø110mm, 216 teeth, zero backlash
Worm Diameter: 17mm
RA/DEC Axles: Ø45mm steel
RA/DEC Bearings: Ø68mm
Motor Type: Precision stepper motors, 1.8°, 128 micro-steps
Motor Resolution: 0.08 arcsec
Periodic Error: <±7 arcsec (typical)
PEC: PPEC (standard CEM40), Real-Time PEC (CEM40EC)
Slew Speed: Up to 4.5°/second
Polar Scope: iPolar electronic polar alignment system
Hand Controller: Go2Nova 8407+, 8-line LCD, built-in heater
Database: 359,000+ objects
Autoguider Port: ST-4
Communication Ports: USB
Power Requirements: 12V DC, 5A
Power Draw: 0.6A (tracking), 0.9A (GoTo)
GPS: Integrated 32-channel
Wi-Fi: External module optional
Cable Management: DC12V (3A), ST-4, USB
Dovetail Saddle: iOptron Universal 5" (Vixen & Losmandy compatible)
Tripod Included: 1.75" LiteRoc stainless steel
Counterweight Included: One 10 lb (4.5 kg) stainless steel
Hard Case: Not included (available separately)
Observing Tip
If you're imaging with a fully loaded refractor, filter wheel, and cooled camera, traditional mounts often get overwhelmed with off-axis weight. The center-balanced design of the CEM40 naturally counteracts the torque from such setups, making it easier to balance and track smoothly. This is particularly helpful when using side-mounted accessories like off-axis guiders or large dew shields that would otherwise create a cantilevered load.
You’ll spend less time fiddling with counterweights and more time actually imaging.
Final Thoughts
The iOptron CEM40 is one of the most thoughtfully engineered equatorial mounts in the under-50 lb payload class. It’s light enough to travel, strong enough to handle heavy imaging payloads, and precise enough to guide with confidence. Its mechanical quality, clever alignment tools, and expansive GoTo functionality make it a true all-around performer for those who need both versatility and reliability in the field.
If you’re ready to take your astrophotography setup to the next level—or you just want a mount that feels as solid and smart as the telescope it carries—the CEM40 delivers.
