iOptron CEM70 Review

The CEM70 Observatory grade, high capacity and sleek. I was surprised and extremely excited when First Light Optics offered me the iOptron CEM70 mount to review. With great jubilee I agreed and for a few months now I’ve been enjoying this heavyweight Centre-Balanced Equatorial Mount.

In this article I’m going to share my thoughts and feelings on this mount.


I’m going to start on a rather vital part of the entire rig. The tri-pier. The tripod, basically. The pier is an optional extra and has to be bought separately. It’s really lightweight and sturdy though. Undoing the bolts enables the legs to be spread and secured.

The steel legs with the pads on conveniently store inside the body of the tri-pier. It can hold 100kg (220lbs). Which is absolutely more than enough for the CEM70 mount and equipment you’d be putting on the mount. It’s sleek and nice and is a great addition to the mount.

The Tri-pier legs store inside the pier itself

One thing I found a bit awkward about the tri-pier legs, though, was how the wing nuts sometimes seemed to slide up and down by their own whims and means. Which was strange. However once it was set up I stored it in the shed , therefore it wasn’t a problem afterwards.

Right, onto the mount now.

iOptron CEM70 Review

Where to start? The iOptron CEM70 is packed full of features from an iPolar system, integrated USB hubs, huge capacity and a dual type saddle just to name a few.

I’ll work from the top down. That seems the most logical.

Dual Type Saddle

The saddle type on the iOptron CEM70 is a dual-type Vixen/Losmandy style. Really convenient as it removes the need for adaptors and gives you versatility if you use multiple telescopes. The locks are spring loaded lugs that hold the dovetails as well, no direct bolt touching so no damage to the bars. The locks also are quite beefy and substantial lugs of metal.

At the rear of the saddle on my model there are no less than 3 DC power ports rated for up-to 3 amps. This is powered by the mains power through the mount. There are also USB ports: two are powered, which connect to the internal USB cable management system.

Finally there’s the iPort, for the optional iOptron CEM70 auto-guiding system. I mentioned this mount has features.

Payload Capacity

The carry capacity for the mount is a whopping 31.8kg (70lbs) without the counterweights. There is a small asterisk about using only 2/3 of this capacity for astrophotography though. I’ve not been able to weigh it down that much to be able to test however. You can see more on the product description on the iOptron CEM 70‘s purchase page But it does seem strong enough that you could image with a higher capacity than 2/3rd.

On the RA axis you’ll find the integrated polar scope. The iPolar system. It’s a fantastic addition. It’s what I would expect on a mount this relatively high end.

No need to move the DEC axis. Just unscrew the cap and then plug in the USB-B on the back of the mount to the computer. Then run the iPolar system. No need for external power, it runs through the USB cable. Similar to the PoleMaster.

The iPolar system uses plate solving to find its location and to perform the polar alignment. Sometimes I wish I could’ve had a live feed like you do on the PoleMaster. But it’s still a very reliable system that worked extremely well and was still quick to setup.

The RA and DEC clutches are… hench. Even though they release and disengage with these rather dainty switches. You can really feel it lock and clunk in place. It feels like some old-school machinery with a satisfying CHUNK. The nice thing also is that you don’t really need to worry about the Home Position. More on that later, but one lock location is the EQ home position. Makes it really easy.

Okay, let me just diverage really fast and talk about setting the Equatorial Home position. You can set quite a few positions in the memory of this thing. From horizontal, to custom, to EQ positions. Although setting EQ home is literally as simple as selecting “Find Zero Position” on the mount. Observe.

Now just save the home position and you’re sorted.

Well. Whilst I’m talking about the hand controller: it’s the Go2Nova 8407. I’m sure those numbers mean a lot to you. It’s a nice hand controller, a bit blocky when compared to the Synscan controllers by Sky-Watcher though. It fits a lot of information on the screen though. 8 lines, 21 characters across. If you’re interested in them specs.

It has over 200,000 objects in its database. NGC, Messier, IC, Solar System, Named Stars, Custom locations and more. It also has a built in heater so on cold nights observing, just hold the controller.

The Back Of The Mount

Okay on the back now we finally have the power port for the mount. The power switch, the ST-4 port (imagine this mount not having auto-guiding built in). USB for computer control, this is the other side of the integrated USB hub, and the hand controller input.

Whilst I really dislike the power port type used since my HEQ5 pro one broke, it is at least on a stationary part of the mount. Just secure the power brick if needed so it doesn’t drag and it should be fine. It isn’t a standard size though like what fits in cooled cameras and the like. It’s a bit thinner. Which is a dislike in my opinion.

This means you’ll need to buy an alternative power cable. Though a power brick is supplied with the mount. If you want to power it off of ancillary gear then you’d need another cable.

The Altitude adjustment is a nice chunky gear. But in a way, I dislike that too. You need to firstly undo the latches on both sides of the adjustment. This is a fantastic way of securing and locking your altitude. Screwing in the adjuster to raise the altitude is nice. You can put the included allen key into this knob to act as a fine adjuster.

It’s when you need to undo it. The mount sometimes will suddenly jolt down as if it hasn’t meshed nicely on the gear and I can’t find an adjustment on it. It also squeaks like a champ. However if this was my mount I would just spray some grease onto that gear though and I’m sure that would sort that right out.

The Azimuth adjustment is nice also. Looking at the markings it seems to be able to adjust 4′ each way. I much more prefer the azimuth adjustment on the CEM70 than I did on the Sky-Watcher EQ6-R Pro. However this mount is in a different category however. I felt these were smooth, the action was easy and fluid. Whereas the action on the EQ6-R Pro’s bolts can be jerky at times.

Using The CEM70

Okay now onto actually using it. Attaching it to the tri-pier is a case of bolting in 2 allen keys onto the pier. This can take a few minutes and if you wiggle whilst pushing the bolts down softly you can easily locate it and begin the screwing procedure.

Polar aligning can be done really quickly by virtue of the aforementioned iPolar system. Super easy, super quick. Super appreciated.

I’m going to review it connected to a PC, set up for astrophotography.

Balancing the load is simple. The included counterweight is a pretty substantial one. I used the mount a lot with my Sky-Watcher 80ED and it’s totally overmounted. I can’t really balance such a light load on this mount. But the iOptron CEM70 really doesn’t care and notice this. Even unbalanced it tracked extremely well.

I decided to test it with unguided exposures. With my Sky-Watcher Evostar 80ED running at 510mm focal length and the ZWO ASI 071MC Pro, which is an APS-C sensor, I was able to get 2 minute unguided exposures. I won’t lie, I was hoping for more since this mount boasts low error and good tracking. But so many factors go into this it’s hard to judge.

One thing that could be done to improve the unguided accuracy is the Permanent Periodic Error Correction training that’s featured with the mount.


The slewing on this mount is rather quiet. It’s not as loud as I first thought. Once you’re outside yes, it’s still sounds loud like all things at 3am. But it’s actually relatively quiet for such a hefty piece of equipment. It can also slew quite fast.

Guiding was a breeze though. Once I had calibrated and was running my PHD often would read 0.4” to 0.6” guidance. That, in my opinion, is really good. It was basically dumb fire. Set it, calibrate it, begin guiding and I didn’t ever have to worry about it afterwards.

I have very little reason to believe why the mount couldn’t maintain such values even with heavier loads though. I really hope I can get a much weightier telescope on it in due time.

It also comes with a foam cut, very sturdy and beefy carry case. Naturally splashed with the company logo. This is a nice addition for sure and it feels really safe in there. I sort of wish they found a way of fitting the counterweight in there also, but then the box would get real heavy real fast.

On the whole, it was really easy to use actually. I was rather surprised at just how simple the CEM70 is to use. For what I guess can be considered observatory grade, really straight forward.

But I did find things to not love.

What Could Be Better?

Firstly, the centre-balanced nature of the mount means there’s a limit to how high you can pull the counterweight up. Whether that’s a bad thing it’s up to you. Yes, the telescope I primarily used was a small one but I also used the StellaLyra 6” and 8” cassegrains on it and balancing was easier and more straight forward. But yes, the weight could strike the body.

As mentioned before, the gear on the altitude adjustment squeaks quite badly. I don’t like that, it just sounds unhealthy. It also sounds as loud as a jet-liner at 3am. Also when you’re really trying to fine tune that polar alignment, the step out can be frustrating.

There didn’t seem to be a hand controller cradle in the box to strap on the mount to secure the controller on. This means you just have to hook the rope handle onto something like the Azimuth knobs.

The tri-pier legs are an anomaly for me. They are secure and sturdy with what seems like built-in vibration suppression. But as I noticed on my guide graph, anytime I walked close to the mount on my patio the graph went nuts. It totally felt my presence there. The Sky-Watcher EQ6-R Pro with the cheap vibration pads I bought seemed more sturdy at times.


Okay. Time to wrap this up.

The iOptron CEM70 is a huge, highly capable, feature ridden go-to equatorial mount. I love, love love the CEM design. I think I prefer it over the GEM design. It can hold a lot of weight, it’s accurate, it’s relatively quiet and it can guide really well.

It’s also expensive.

The mount, alone, without the pier is £2698 or £3095 with the iGuider system. The tri-pier is a further £635. That brings this pricetag to £3333 without the iGuider, or £3730 for the iOptron CEM70 system. But I suspect it’s a mount you’re going to have for a very, very long time. Due to its capabilities. If you’re decking out an observatory as well it could be a worthwhile investment.

I wish the unguided performance was better. But as mentioned, too many factors go into that and PPEC might make it better. It’s weighty as well. It’s quite heavy to move fully made up.

It takes a few minutes to even set up the mount to bolt it on the pier. I suspect though when iOptron designed this mount, they weren’t expecting it to be setup and tore down each night. But it does make for a very firm and secure fitment to the mount. The flat bottom is also excellent as it isn’t awkward when trying to fit.

In short I’m absolutely in love with this mount. There are some irritating small things. If I moved the mount when it was really out of balance, it binded and complains at you. The smaller power port, the squeaking on the gear. Little things let this down.

But things like finding the home position, great guiding performance, the iPolar system. The integrated USB hub. There’s a lot to like. It’s feature packed and if you’re budgeting that kind of change for a mount I think you’ll find great joy with the iOptron CEM70.

Will I ever get one? Not any time soon! I certainly can’t afford it. If I had an observatory then yes I would really consider it though. It can be a pain to break down and setup each night but really with the longer nights coming in, it’s less of an aggravation. You can find links to this item in the video description.

I hope you’ve found this review helpful, and that if you go on to purchase an iOptron CEM70 you find great success with it!

If you rather watch the video review, then you can find it on YouTube below.

Clear skies, keep looking up and keep them cameras clicking.

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