iOptron GEM28 go-to German Equatorial Mount with Hard case and 1.75" LiteRoc Tripod

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iOptron's compact next-generation GEM28 mount is a tiny titan with a 28 pound payload capacity.
Our Product #: G282B3
iOptron Product #: G282B3
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Product Description

This iOptron Gem28 German equatorial mount has:
Built-in dual-axis go-to computer drive with 212,000+ object database
Built-in Wi-Fi
Permanent periodic error correction and ST-4 autoguider port
28 pound maximum payload capacity
Built-in illuminated AccuAlign polar finder scope
Adjustable height tripod with 1.75" diameter stainless steel legs

The iOptron GEM28 mount is a very portable and affordable high precision German equatorial mount for entry-level and intermediate astronomers. It is ideal for go-to visual observing and long exposure astrophotography with many of the most popular short focal length refractors and smaller reflector optical tubes.

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.

Drive system details: The synchonous 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 adatper.  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.

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 with their names and more; plus 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 come 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.

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 tripod has 1.75" diameter stainless steel legs, yet weighs only 13 pounds (4.8kg). It is very solid and stable, able to support the GEM28 equatorial head and even the heaviest rated payloads with ease.

Optical tube mounting method: The mount head accepts industry-standard Vixen-style dovetails.

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.

Mount German Equatorial Mount
Payload * 28 lbs (12.7kg), exclude counterweight
Mount weight 10 lbs (4.5kg)
Payload/Mount weight 2.80
Structure Material All metal, Casting + CNC machined
Exterior Finish Powder coating
Periodic error (PE) ** <±10 arcsec
PEC Yes, Permanent PEC
Worm period 600 sec
Right Ascension worm wheel Φ88mm, 144 teeth aluminum
Declination worm wheel Φ88mm, 144 teeth aluminum
Right Ascension axis shaft Φ35mm steel
Declination axis shaft Φ35mm steel
Right Ascension bearing Φ55mm ball bearing
Declination bearing Φ55mm ball bearing
Worm gears Φ15.2mm, Brass
Motor drive 1.8º stepper motor, 128X microdivision
Resolution 0.17 arc seconds
Transmission Synchronous belt
Latitude adjustment range 10º ~ 70º
Azimuth adjustment range ± 6º
Polar Scope AccuAlignTM optical polar scope
Level indicator Level bubble
Hand Controller Go2Nova® 8409 with ~212,000 objects database
Tracking Automatic
Slew speed 1×,2×,8×,16×,64×,128×,256×,512×,MAX(6º/sec)
Power consumption 0.6A(Tracking), 0.9A(GOTO)
Power requirement 12V DC, 5A
AC adapter 100V ~ 240V (included)
Power-down memory Yes
Wi-Fi Built-in
Communication port Yes (Wi-Fi and USB)
Autoguide port Yes (ST-4 compatible)
Firmware upgrade Yes
PC computer control Yes (ASCOM)
Counterweight shaft Φ20X200mm (M16), Stainless Steel
Shaft extension Φ20X120mm (M16), Stainless Steel
Counterweight 10 lbs (4.5kg)
Tripod 1.75" Stainless Steel (5kg)
Dovetail saddle 3.8" Vixen-style, center adjustable
Carrying case Optional
GPS Optional external 32-channel GPS
Autoguiding Optional external iGuider 1
Operation temperature -10ºC ~ 40ºC
Warranty Two year limited

Tech Details

Weight 36 lbs.
Warranty 2 years


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