iOptron GEM45 Mount

45 lb Payload on a 17.5 lb Mount Head

The GEM45 achieves its 2.53 payload-to-weight ratio through an all-metal, CNC-machined structure and oversized core components. Both the Right Ascension and Declination axes are built around solid Φ45mm steel shafts and large Φ68mm bearings, providing the rigidity to carry heavy instrument packages without sacrificing stability. The 17.5 lb mount head is easy to transport to dark-sky sites, yet it supports imaging systems up to 45 lbs, from long refractors to 8" and 9.25" SCT or R-C setups with cameras and guide scopes.

<±7.5 arcsec PE Standard, <0.3 arcsec RMS with the EC Encoder

At the heart of the GEM45's tracking system are two Φ110mm, 216-tooth brass worm wheels engineered for zero backlash. Driven through a synchronous belt by a 1.8° stepper motor with 128 micro-steps, the system achieves a resolution of 0.08 arcseconds. On the standard GEM45, this drivetrain delivers a native periodic error of less than ±7.5 arcseconds, which can be further reduced with Permanent Periodic Error Correction (PPEC) for smooth, tightly guided long exposures.

GEM45EC versions add a high-resolution encoder and Real-time PEC (RPEC) that correct worm gear error as it happens, for a native tracking accuracy of less than 0.3 arcseconds RMS. This level of precision can eliminate the need for autoguiding on short-to-medium exposures, even with long focal length telescopes, and makes guiding smoother when you do use it.

Go2Nova Controller with a 212,000+ Object Database

Navigating the night sky is managed by the Go2Nova® 8407+ hand controller, which contains a database of over 212,000 celestial objects on an 8-line LCD. Once aligned, the mount can slew to any target at up to 4.5° per second. An integrated GPS automatically inputs the correct time and location, and the ST-4 guiding port and USB communication port provide standard connectivity for autoguiding and computer control.

Integrated iPolar and 3A Power for Cable Management

The GEM45 is designed to minimize setup time and potential cable snags. The built-in iPolar electronic polar scope provides fast, highly accurate polar alignment directly on your computer screen, even when Polaris is obstructed. An advanced cable management system offers a DC12V (3A) power port, a USB port and an ST-4 guide port near the dovetail saddle, so you can power cameras and accessories without loose wires hanging from the telescope. Power draw is only 0.6A while tracking, extending battery life on long nights at remote sites, and the mount operates from -10°C to 40°C.

• Universal Saddle Plate: The 6" dual saddle accommodates both Losmandy-D and Vixen-style dovetail bars, so you can switch optical tubes without changing adapters.
• Automatic Zero Search: The mount automatically finds its mechanical zero position, which is critical for accurate GoTo performance and remote operation.
• Power-Down Memory: If power is accidentally disconnected, the mount remembers its position and alignment, so you can resume your session without starting over.

Choose Your GEM45 Version

All versions share the same 45 lb payload, 17.5 lb mount head, internal iPolar, Go2Nova hand controller, counterweight shaft and AC adapter. They differ in tracking accuracy (standard or EC encoder), in whether a LiteRoc tripod and counterweight are included, and in accessories such as the hard case, iGuider or NUC-ready saddle.

• GEM45 w/ iPolar & LiteRoc: The essential imaging package with the 1.75" LiteRoc stainless steel tripod and an 11 lb (5 kg) counterweight. No hard case is included in this version.
• GEM45 w/ iPolar, Case & LiteRoc: The same complete package plus a hard carrying case, the best all-round choice for imagers who travel to dark sites.
• GEM45 w/ iPolar, iGuider, Case & LiteRoc: Adds the iGuider guiding camera built into the dovetail saddle, for autoguiding without mounting a separate guide scope and camera.
• GEM45 NUC-Ready and GEM45EC NUC-Ready (w/ iPolar, Case & LiteRoc): A saddle ready to carry an Intel NUC mini computer at the front, with dedicated NUC power, LAN and USB connections in the cable management system. The NUC computer itself is not included.
• GEM45EC w/ iPolar, Case & LiteRoc: The encoder version with <0.3 arcsec RMS tracking, for unguided imaging, scientific work such as photometry, or imagers who want the most precise tracking before adding a guider.
• GEM45 Head Only and GEM45EC Head Only (w/ iPolar & Case): The mount head, hand controller, counterweight shaft and AC adapter in a hard case. No tripod and no counterweight are included, making these ideal if you already own a LiteRoc tripod, a pier or suitable counterweights.

iOptron GEM45 vs. CEM40: 45 lbs vs. 40 lbs and Two Mount Designs

The GEM45 and its sibling, the CEM40, offer similar payload capacities but different design philosophies. The choice depends on your primary use case and telescope type.

• iOptron CEM40 Advantage: The center-balanced design places the telescope's center of gravity directly over the tripod, increasing stability for its weight. It also allows operation at very low latitudes without the counterweight shaft colliding with a tripod leg.
• iOptron GEM45 Advantage: The classic German equatorial design is familiar and intuitive to balance, and it provides maximum clearance for long optical tubes such as refractors, so the back of the telescope will not strike the mount or a tripod leg near the meridian and zenith. The GEM45 also carries a slightly higher payload of 45 lbs compared to the CEM40's 40 lbs.