iOptron CEM120 Center Balanced EQ Mount

  • 115 lbs payload capacity
  • Tracking accuracy of less than 0.15 arcsec RMS
  • 12 port cable management saddle
  • LAN, RS232, USB and Wifi Control options for remote observatory setups
  • Built-in 32 Channel GPS 
  • Note: If you are going to mount this atop an already purchased Tri-Pier (8034) you will need an adapter plate #IO-8036-120. (You can find this below in the Recommended Products card.) Otherwise we advise to get the IO-8037 Tri-pier which already had the adapter plate attached.

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    iOptron CEM120 Center Balanced EQ Mount

    Mount Specs:
    • Mount: Center-balanced Equatorial Mount (CEM)
    • Payload: 52kg (115 lbs), excludes counterweight
    • Mount Weight: 26kg (57 lbs)
    • Payload/Mount weight ratio: 2/1
    • Material: All metal
    • Latitude Adjustment Range: 0- 68 deg (0.5 arcmin division)
    • Azimuth Adjustment Range: (+/-) 5 deg (3 arcmin division)
    • Tracking accuracy (PE): < (+/-)3.5 arcsec
    • Worm Period: 240 sec
    • PEC: Permanent PEC
    • Right Ascension Worm Wheel: 216mm, 360 teeth, zero backlash
    • Declination Worm Wheel: 216mm, 360 teeth, zero backlash
    • Worm: 26mm
    • Right Ascension Axle: 80mm, steel
    • Declination Axle: 80mm, steel
    • Right Ascension Bearings: 125mm
    • Declination Bearings: 125mm
    • Counterweight shaft: 38.1x 540 mm (SS, anti-slip, 4.5kg)
    • Counterweight: 10 kg (22 lbs)
    • Mount Base Size: 210 x 230 mm
    • Motor Drive: Precision stepper motor w/128 micro-step
    • Resolution: 0.07 arc seconds
    • Slew speed: 4°/sec (960x) max.
    • Hand Controller: Go2Nova 8407 V2, 8 line 21 character LCD
    • Power Requirement: DC 12V, 5A
    • Power Consumption: 0.7A (Tracking), 1.8A (GOTO)
    • Polar Scope: Optional electronic polar scope
    • Meridian Treatment: Stop (0-14 deg pass), auto flip
    • Zero Position: Automatic zero search
    • Park Position: Horizontal, vertical, current, alt/azi input
    • Level Indicator: Yes
    • Dovetail Saddle: Losmandy D, 17.2" (437mm)
    • GPS: Yes
    • Guiding Port: ST-4
    • Communication Port: RS232, USB, LAN, WiFi
    • Cable Management: 2xDC12V (1A), DC5V(1A), 2xDC (5A), ST4, 6P6C, 4xUSB2.0, USB3.0 (powered), USB for PS, AUX
    • Pier/Tripod: Optional pier
    • Warranty: Two year limited


    With the growing demand for accuracy, heavy capacity, stability, and versatility in an equatorial mount, iOptron created the CEM120 to meet all these needs. The CEM 120 like all center balance designs are naturally stable is due to putting the weight of the telescopes directly over the center of the pier or tripod.

    The mount’s performance is demonstrated by its low periodic tracking error that is +/- 3.5 arc seconds RMS. The CEM120 features an advanced cable management system consisting that prevents tangle ups and reduces the chance of fractured cables. It also adds some new features to the CEM family like Wi-Fi and LAN for remote operation.


    Azimuth Range Plus or minus 5 degrees
    Dec Worm Wheel216mm/360 teeth
    Free ShippingYes
    Head DesignEquatorial
    Instrument Capacity115 lb
    Latitude Range 65 degrees
    Mount Head Weight52.6lb
    RA Worm Wheel216mm/360 teeth
    Saddle WidthD Series
    Telescope ConnectionLosmandy Style
    Tracking ModesEQ North & EQ South
    Tracking RatesLunar & Sidereal & Solar
    Warranty2 Year Warranty
    weight57 lb
    Worm Period240 seconds


    • CEM120 mount head x1
    • Go2Nova 8407 V2 hand controller x1
    • 10 kg counterweight x2
    • Counterweight shaft x1
    • Hand controller cable x1
    • Serial cable (#8412) x1
    Customer Reviews
    4.5 Based on 4 Reviews
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    Filter Reviews:
    Dave B.
    United States United States
    Nice Mount

    I've only had it out twice due to the poor weather, but it performs nicely. Tracking is very good. I was able to go unguided for 240 seconds with my 10" RC @2,000mm focal length without PEC training. Not all images are keepers, but @ 120 seconds I was able to use all images. Looking forward to some clear nights to fine tune everything. I'm running it as an ASCOM mount with The Sky X Pro. I really like the way the gears engage. I upgraded from the CEM60 and don't miss the magnetic locks.

    John E.
    United States United States
    Great mount with a bug or two..

    This mount has exceeded my expectations in all ways except for two - every other time I power it up, it reports a main board error. But every other other time, it is perfect. It maybe reports the wrong azimuth to my dome software (even though the number looks correct) and my slit keeps being sent to the opposite side of the sky from the scope. Crazy.

    A OPT Telescopes Customer
    Mark R.
    United States
    Well designed mount!

    I've had enough time to properly explore enough of this mount to say it performs as expected. It's well built with an awesome payload rating. I guide no matter what, but for being the non-ec version, it performed well during a few unguided tests. I do recommend this for anyone looking for a higher payload capacity mount but doesn't want to spend double, if not triple, on other mounts in it's weight range. And of course, as always, OPT has substantial customer service. They always have an answer or solution to my inquiries/questions that I have for them, plus the shipping is fast and cheap.

    iOptron CEM 120

    Pros: 1.Axle locking system and Drive engaging systems are good. 2.Very silent operation. Cons: 1. Base plate and M8 fixing screws looks too thin and small for such a mount of heavy payload. 2. For short refractors , the focusser knobs will touch the mounting plate while using angle adjuster. 3. Should have provided shroud covers for the Electrical connection boxes. 4. Locking screw (May be a grub screw with nylon tip ) should help CW shaft from rotating , especially while using Rectangular counter weights. 5. An interlocking system to prevent Gear engaging knob engagement while Axle lock is engaged may help prevent mis -operation