A Compact and Capable GoTo Mount for Visual and Imaging Applications on the Move
The iOptron GEM28 G282B3 is the perfect intersection of portability, precision, and proven design. With a generous 28-pound payload capacity, integrated AccuAlign™ polar scope, and LiteRoc stainless steel tripod, this lightweight German equatorial mount is ideal for mobile astronomers and those building an entry-level astrophotography setup. Whether you're imaging under dark skies or observing from the backyard, the GEM28 delivers professional-grade tracking and GoTo accuracy in a package that’s easy to pack, set up, and trust.
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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LiteRoc heavy-duty stainless steel tripod (7.5kg)
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Die-cast metal tripod spreader with accessory tray
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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 comes with a 10 pound (4.5kg) counterweight, an 8" x 20mm counterweight shaft, and a 5" x 20mm counterweight shaft extension. These can be combined to hold the GEM28's maximum payload of 28 pounds (12.7kg). However, most astrophotographers will probably want to limit the instrument payload to a maximum of about 20 pounds, to benefit from the increased stability of having a smaller instrument on an over-sized mount—ideal for compact refractors and portable imaging rigs.
Drive System Details:
The synchronous belt transmission of the GEM28 has a 144-tooth 88mm diameter drive gear in right ascension and a 144-tooth 88mm diameter drive gear in declination. Brass worm gears are standard. Both the right ascension axis and declination shaft are 30mm in diameter.
The standard equipment dual-axis stepper motors with encoders provide 0.17 arc second per step resolution, assuring an imperceptible stepping motion during visual observing and imaging. Available user-selected tracking rates include sidereal, solar, lunar, King, and a user-defined speed. User-adjustable backlash compensation is standard.
There are nine guiding, centering, and slewing speeds available: sidereal and 2x sidereal for guiding; 8x, 16x, 64x, and 128x sidereal for centering; and 256x (1°/sec), 512x (2°/sec) sidereal, and a maximum speed of ~4°/sec for slewing.
The iOptron GEM28 comes with an AC adapter. It also comes with an RS232 cable and port for mount firmware upgrade and ASCOM control using an optional computer. Strain relief power cord cable protection is standard.
GoToNova® Hand Controller:
The supplied GoToNova technology computer hand control has a more than 212,000 object go-to database that includes: 60 named deep sky objects; the 110 object Messier Catalog; the 7,840 object NGC Catalog; the 5,386 object IC Catalog; the 12,921 object UGC Catalog; the 30,642 object MCG Catalog; the 109 object Caldwell Catalog; the 4,076 object Abell Catalog; the 400 object Herschel Catalog; 15 comets; 195 named stars; 210 double stars; 38,528 GCVS variable stars; the SAO catalog; 116 asteroids; the 88 modern constellations; and 60 user-defined objects.
Permanent periodic error correction (PEC) for astrophotography is built in. HBX ports are provided for an optional ST-4 type autoguider, a PC, and auxiliary components. It uses a new command set that is completely open for user-defined control of the mount. The mount also comes with WiFi as standard equipment allowing the modern day user a multitude of ways to connect to the mount.
The GoToNova hand controller has the largest LCD screen on the market, with an 8 line/21 character display and backlit LED buttons. A heating mechanism in the hand control provides display visibility at a temperature as low as 4° Fahrenheit (-20°C), the lowest working temperature among commercially-available computer hand controls.
Mount Details:
The GEM28’s mount is built to be strong, yet small and light, to satisfy both stability and portability needs. The equatorial head, not counting the standard equipment 10 pound (4.5kg) counterweight, weighs only 10 pounds (4.5kg) for the highest payload to mount weight ratio in its category (2.80). The mount head comes standard with a hard case for easy transport—an advantage for observers who travel to dark-sky sites or stow their gear between sessions.
The mount is designed to operate in both northern and southern hemispheres at latitudes from 10° to 70°. A large adjustment control between the vertical side pieces of the mount and an indicator window in one of the side pieces makes it easy to align the mount on the celestial pole in altitude. Twin adjustment knobs in the base of the mount let you fine-tune the azimuth alignment on the pole over a +/-6° arc.
The standard equipment AccuAlign™ LED-illuminated polar alignment finderscope will let you align the scope on the celestial pole with very high accuracy. There is a built-in bubble level for leveling the mount for the most accurate tracking.
Tripod:
The supplied adjustable height LiteRoc tripod has 1.75" diameter stainless steel legs, yet weighs only 13 pounds (5.9kg). It is very solid and stable, able to support the GEM28 equatorial head and even the heaviest rated payloads with ease. The LiteRoc tripod is ideal for field astrophotography setups where portability and rigidity are equally important.
Optical Tube Mounting:
The mount head accepts industry-standard Vixen-style dovetails, allowing easy compatibility with a wide variety of optical tubes—particularly lightweight ED refractors, Maksutovs, and imaging Newtonians under 20 lbs.
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:
The GEM28 is a standout performer when paired with high-quality 80–102mm apochromatic refractors for imaging. For travel setups, the included hard case makes it especially convenient to fly or drive with. Use the AccuAlign polar scope when Polaris is visible, and enjoy rapid setup with minimal fiddling—even from remote or semi-rural locations. Add a lightweight guider and the optional iGuider system, and you'll be ready to collect pinpoint stars all night long.
Final Thoughts:
The iOptron GEM28 G282B3 is an exceptional choice for astronomers who want more than a starter mount but aren’t ready to commit to full observatory weight. With a clean design, proven engineering, and premium accessories—including the LiteRoc tripod, AccuAlign polar scope, and hard case—this version of the GEM28 offers a complete mobile GoTo solution that’s easy to travel with, yet serious enough for deep sky imaging.
Whether you're upgrading from a star tracker or expanding your toolkit with a reliable portable equatorial mount, the G282B3 earns its place as a capable, well-rounded performer.
