iOptron CEM 120 Review

CEM120 First Impressions:

(49) 30" unguided images - stacked - Sony QX1 - Orion 8" Newtonian with Coma Corrector

(1) 10 Minute guided image - Atik 490EX Color - Orion 8" Newtonian with Coma Corrector

CEM Unboxing Video:

At we offer informative product unboxing, reviews and how to videos for products that relate to astronomy and astrophotography.

An avid photographer for many years, I began my astrophotography journey 3 years ago.

My first telescope of note was an old Tasco 80mm Refractor that my good friend and I purchased in 1987… the journey continues.

My full-time job is in the technology space and my hobbies range from designing, building and flying experimental aircraft, photography, radio control aviation, astronomy, multi-media production and boating.

The CEM 120 has finally arrived – be sure to check out my unboxing video that is included on the blog. Make sure you subscribe to my channel of course give the video a Like.

Some Background

This is not a paid review. All thoughts opinions, bad grammar and unclear points are mine.

As I learn more about the features, benefits and shortcomings of the CEM 120, I will offer updates to this blog. But I wanted to make sure to share my initial experience with it now.

So why did I choose this mount in the first place? I have been involved with photography for many years and shoot currently with a Nikon D810 – as my primary camera. I focus on landscape, nightscape and aviation as my primary subjects.

My first real astrophotography setup was purchased in 2014 and consisted of a Celestron CGEM with an Edge HD 8” scope with Hyperstar and a focal reducer to provide flexibility - depending upon the subject I was imaging - with this setup, I worked my way up to better cameras.

I have always taken one-shot color with all its inherent limitations… as a side note, I live in Northwest Ohio in the United States and we get very few days to image so I want to have usable data in the event of clouds or weather changes. After hyper-tuning my CGEM I have been satisfied with it and it certainly helped me determine if this would be a passing fad or a long-term hobby.

Fast-forward to 2017 and the opportunity to upgrade my OTA from the 8” Edge HD to an 11” Edge HD along with hyperstar – minus the focal reducer. The downside is the added weight of this setup was pushing the mount to its limits and I started running into guiding issues. I would occasionally remove some of the accessories from the OTA (guide camera and auto align) that allowed me to calm the mount down. This technique gave me useable data with the fast setup that Hyperstar provides in 30” or less exposures so it has not been as big of an issue – especially with the addition of the PoleMaster camera for better polar alignment.

Why Choose the CEM 120

Simply stated, I wanted more – adding an additional refractor on my OTA to image with two cameras was out of the question and moving to a large reflector with filter wheel/mono images always felt like a potential barrier with my existing setup.

Enter the CEM 120 – I considered other mounts, I looked at the budget, I looked at features and I read what reviews I could find… and I landed on this mount. I am certain that other well-known mounts would fit the bill… in fact it was never in question… so it came down to a price vs. features vs. payload – and did I mention price…

Before you stop reading and flame me with that statement – let me be very clear – price is NEVER the final consideration – even though it factors significantly. It’s analogous to a three-legged chair – price being one of them.

Take out a leg (cost) as in long-term cost of lost time due to mechanical reliability, repairs, replacement part cost, and time spent not collecting data on precious few nights and you end up with the all-important true cost of ownership. I decided this product could deliver without a SIGNIFICANT risk – even with little information being available at the time of acquisition.

There is another critical factor – I have been impressed with my experience with my iOptron SkyGuider mount and tripod that I bought several years ago. This is a solid piece of engineering and reliable, and the iOptron customer service is fantastic.

So moving onto the next steps for me: I will do a follow up video on how to setup and use the mount. Beyond the unboxing that I captured in the video, I have now fabricated a mounting plate for my tripod and my thoughts to this point will be captured below.


The mount is certainly a beast – at 57 lbs. without the counterweight bar and counterweights, puts it right on the portability threshold for me. You should expect some mass to this mount with the rated payload ability. Long range I will be adding this to a pier in a dome in my back yard. I don’t plan on doing any long distance control although I may offer this option to some of my friends.

The quality is instantly evident (aside from the box quality that I am happy to report iOptron addressed immediately as they told the factory to make a change on future box quality after seeing my unboxing video) – the mount is sturdy, no rough edges or sloppy finish with this mount. The machining is clearly well done and the fittings and presentation is very nice… nothing seems cheap or put on as an afterthought. I don’t see any evidence at this point of iOptron taking any shortcuts to replace some of the parts with cheap materials.

The internal cabling has shielding to prevent chafing and is a nice touch. And the packaging was done to a level that I plan on re-using in a roll-around box to reduce back stress to move the mount outside until I have a more permanent location.

An additional item worth mentioning is the User Interface of the hand controller. I have been in the software/graphics industry most of my career and it is ease of use is impressive. I jumped right in and was moving through the interface immediately with no reference to the user manual. Very well thought out -- and not one of the more discussed points when doing product reviews -- but a janky interface can be a major frustration point. This hand controller is well designed.

Compared to my CGEM, there is really no comparison and these mounts are not in the same class – the CGX-L would be a fair comparison and I have commented on why I chose iOptron over the Celestron. If I have the opportunity to do a head-to-head comparison with some of the competitors I will note that going forward.

There are some direct feature comparisons that are worth mentioning.

  • It is clear that there is a market for a higher payload class mount in the $3,000-6,000 price range, so the options for mounts in this category are now available with features like internal cable management.

  • As we hang more electronics on the OTA and mount - this is clearly an important feature, power consumption in the servo vs. stepper motor debate, good PEC out of the box, ST4 guiding capability and Wi-Fi/remote control of the mount are all part of the feature set/discussions that I factored into the decision.

  • Advanced ports and the number of available power plugs for additional accessories are also part of the conversation. This mount has them all, along with built in GPS that some of the competitors require as an additional accessory. A current bonus that has caused some discussion/questions online is the inclusion of a second 22lbs. (10kg) counterweight.

  • The way the USB 2 ports work is effectively a 4-port USB hub built into the dovetail. Multiple cables plug in and it uses one cable out to your computer. Only one USB 3 port is included – an additional one would have been nice.

The manual says that it will come with two counterweights for a limited time… no mention of how long this will be offered but it is listed as a $118 part on the website so this is a great additional value while it lasts.

Final point of note – the user manual is well done – I downloaded it and read it many times before I even got the mount – some of the questions I had on the cable management system were pointed out – but not as clear as I needed them to be without the mount in front of me. Once I opened the box and looked at the mount, it became clear what the user guide was referencing and I will address this in the how-to video.

Pros and Cons


  • The mount is heavy but well built and still fits into the portability discussion (barely)

  • Feature rich with multiple ports and power options for improved cable management

  • Payload capabilities at 115 lbs. rated load without counterweights

  • Built in Wi-Fi

  • Built in RJ45 Ethernet port

  • Built in GPS

  • Features both USB 2 ports and 1 USB 3 port

  • Integrated PoleMaster capability with additional $39 adapter

  • Easy to use hand controller user interface – well done!

  • Built in heater for the hand controller

  • Standard Losmandy dovetail

  • Meridian Flip programmed into the hand controller

  • Home position for remote control

  • Two-year warranty

  • Good quick start guide and User Manual – see note above

  • Great customer service

  • Affordability for its capabilities

  • Free counterweight offer


  • Heavy – really a pro and a con

  • No easy grab positions – this will be an even greater challenge when the counterweight bar is attached so factor this into the portability formula – if someone has a suggestion for me on this, I’m happy to hear it.

  • Wi-Fi password was not indicated in the documentation – quick email fixed that issue

  • Additional USB 3 ports would be nice

Final Thoughts

In conclusion at this point in time (early days indeed) I am satisfied with the mount and feel that there will be many great opportunities with this mount. Far more pros than cons at this point. To be fair, the proof will be in how it performs in the field and over time… and that of course will take some time. As I gain more experience, I will continue to update my notes.

I believe that this mount offers a great value and quality/capability level for how I intend to use the mount… as an advanced amateur astrophotographer and occasional visual user.

Let me know what you think about this review and any observations you have of your CEM 120 or similar mount.

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