Lightweight Portability Meets GEM-Class Precision
The iOptron GEM28 G281B1 is a feature-rich, portable German equatorial mount built for visual observers and beginner astrophotographers who want serious performance without serious weight. Outfitted with the AccuAlign™ illuminated polar scope and mounted atop iOptron’s 1.5" heavy-duty stainless steel tripod, this configuration delivers solid GoTo performance and stable tracking in a compact footprint. Whether you're building your first imaging rig or upgrading from a simple star tracker, the GEM28 is a mount that grows with you.
iOptron's compact next-generation GEM28 mount is a tiny titan with a 28 pound payload capacity.
This iOptron Gem28 German equatorial mount has:
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German equatorial design, latitude range of 10° ~ 70°
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Ideal for both visual observation and astrophotography
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Low periodic error (< ± 12 arc seconds)
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Payload of 12.7 kg (28 lbs) with the mount-only weight of 4.5 kg (10 lbs)
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CNC machined and cast metal body
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Spring loaded gear system
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Large easy to use quick-lock gear clutches
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Stepper motor with low power consumption
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AccuAlign™ calibrated polar scope
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Polar alignment routine for those who can’t see the Pole Star
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Go2Nova® 8409 controller with Advanced GOTONOVA® GOTO Technology
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Integrated ST-4 autoguiding port
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Built-in Wi-Fi
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USB port for firmware upgrade and computer control
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Standard 1.5 inch heavy-duty stainless steel tripod (5kg)
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Die-cast metal tripod spreader with accessory tray
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Optional hard carrying case
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Optional 32-channel Global Positioning System (GPS)
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Optional iGuider™ autoguiding system (#3360)
Payload Capacity:
The GEM28 includes a 10-pound (4.5kg) counterweight, an 8" counterweight shaft, and a 5" extension—together supporting its full 28-pound rated payload. For most portable imaging setups, keeping the payload closer to 20 pounds helps ensure tighter guiding and better overall performance in the field.
Drive System Details:
The mount’s synchronous belt-driven transmission includes 144-tooth 88mm aluminum RA and Dec gears, paired with brass worms and 30mm steel shafts. The result is smooth, quiet motion and long-term tracking reliability.
The high-resolution dual-axis stepper motors deliver 0.17 arcsecond step resolution, ideal for entry-level astrophotography setups. Tracking modes include sidereal, solar, lunar, King, and user-defined, with nine slew speeds up to ~4°/sec.
The GEM28 comes with a 100V–240V indoor-use AC adapter, RS232 cable, and strain-relief power cord protection. It supports full control via ASCOM, INDI, and popular astronomy software platforms.
GoToNova® Hand Controller and Object Database:
The supplied GoToNova® 8409 hand controller is a powerful and user-friendly control system with a built-in database of over 212,000 celestial objects, including:
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60 named deep sky objects
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110 Messier objects
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7,840 NGC objects
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5,386 IC objects
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12,921 UGC objects
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30,642 MCG catalog entries
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109 Caldwell objects
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4,076 Abell galaxy clusters
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400 Herschel deep sky targets
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15 comets
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195 named stars
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210 double stars
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38,528 GCVS variable stars
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The complete SAO catalog
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116 asteroids
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All 88 modern constellations by name
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Plus 60 user-defined objects
The GoToNova controller also includes a large 8-line, 21-character LCD screen, red LED backlit keys, and a built-in heater for cold-weather readability down to -20°C (-4°F).
Permanent periodic error correction (PEC) is built-in to improve tracking during long-exposure astrophotography. The mount includes HBX ports for an ST-4-compatible autoguider, PC connection, and auxiliary accessories. The command set is fully open, making the GEM28 compatible with ASCOM, INDI, and third-party control software.
Wi-Fi connectivity comes standard, giving you full mount control via smartphone, tablet, or computer using apps like SkySafari, iOptron Commander Lite, or other wireless platforms.
Mount Head and Alignment:
The GEM28 mount head weighs only 10 pounds (4.5 kg) and offers a class-leading 2.8:1 payload-to-weight ratio. Altitude and azimuth adjustment knobs offer ±6° of fine tuning, and the standard AccuAlign™ illuminated polar scope allows precise polar alignment using Polaris or Sigma Octantis.
Tripod:
The included 1.5" heavy-duty stainless steel tripod provides lightweight support for travel and grab-and-go sessions:
Mounting:
The GEM28’s 3.8" Vixen-style dovetail saddle is center-adjustable and compatible with most refractors, small SCTs, and compact imaging Newtonians.
If you're looking for a stable, high-precision, mid-capacity German equatorial mount—yet one that is reasonably portable and reasonably priced—take a careful look at the iOptron GEM28. It may be just what you are looking for.
Observing Tip:
If you're planning to use the GEM28 on grass, sand, or dirt, consider adding ground spikes or rubber tripod feet to improve footing with the lighter 1.5" tripod. For astrophotography, use a short refractor under 600mm focal length to maximize the mount’s accuracy and keep guiding simple, especially when imaging unguided for short exposures.
Final Thoughts:
The GEM28 G281B1 is a true gateway mount for aspiring imagers or experienced observers who want something compact and capable. With the AccuAlign polar scope, GoToNova hand controller, and a travel-friendly 1.5" tripod, it’s ready for remote dark-sky trips or backyard observation alike. It doesn’t get much easier—or lighter—than this when stepping into the world of serious celestial tracking.
