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iOptron CEM120 Centre Balanced EQ GOTO Mount

iOptron CEM120 Centre Balanced EQ GOTO Mount
iOptron CEM120 Centre Balanced EQ GOTO MountiOptron CEM120 Centre Balanced EQ GOTO MountiOptron CEM120 Centre Balanced EQ GOTO Mount
Price:  £4,845.00(Inc. 20% VAT)

Model:  7300
Brand:  iOptron



Generally In Stock, Please Confirm Before Ordering

2 Year Warranty On All New Items
(Excluding Batteries & Globes)

  (1 Review)

The All NEW iOptron CEM120! 

An extraordinary innovation in mount design...Now with a new payload! 

Recognizing the growing demand for an accurate and stable, equatorial mount with the versatility to carry larger instruments and more complex imaging arrays, we created the iOptron CEM120. It offers the benefits of our revolutionary “center balance” design: stability, accuracy, and smooth mechanical operation, while capable of carrying a payload up to 115 lbs (52 kg). The “center balance” design’s natural stability is due to its focusing the mount along with payloads weight directly over the center of the pier or tripod. 

The CEM120's performance is demonstrated by its low periodic tracking error of ±3.5 arc seconds. Along with the stability aspect, the CEM120 features an advanced cable management system consisting of more ports in more locations preventing tangle ups and reducing the chance of fractured cables. It also adds some new features to the CEM family like Wi-Fi and LAN for remote operation and easy to use, reliable clutches on both axes. 

Optional heavy duty Tri-Pier 360 and Permanent Pier are available for order. 

A new design, center-balanced equatorial mount (CEM) for maximum payload with natural stability
Observatory astrophotography mount ideal for both visual and Astro-photographers
Payload of 115 lbs (52 kg) with the mount weight of 57 lbs (26 kg)
Easy to use and reliable gear clutches
Precision altitude and azimuth adjustment.
Precision stepper motor with 0.07 arcsec accuracy for precise GOTO and accurate tracking
Polar alignment routine for those who can't see the Pole Star
Go2Nova® 8407 V2 controller with Advanced GOTONOVA® GOTO Technology with built in heater
High precision tracking with low periodic error (PE)<±3.5 arcsec
Permanent periodic error correction (PPEC)
32-channel Global Positioning System (GPS)
Built-in WiFi and LAN for remote operation
Integrated ST-4 autoguiding port
Advanced cable management system with more choices
Spring loaded, individual adjustable Losmandy saddle

CEM120 mount head x1
Go2Nova 8407 V2 hand controller x1
10 kg counterweight x1 (free extra one for limited time)
Counterweight shaft x1
Hand controller cable x1
Serial cable (#8412) x1

Mount       Center-balanced Equatorial Mount (CEM)
Payload       52kg (115 lbs), exclude counterweight*
Mount weight       26kg (57 lbs)
Payload/Mount weight ratio       2
Material       All metal
Latitude adjustment range       0°~ 68° (0.5 arcmin division)**
Azimuth adjustment range       ± 5° (3 arcmin division)
PE (by encoder)       < ±3.5 arcsec
Worm period       240 sec
PEC       PPEC
Right Ascension worm wheel       934;216mm, 360 teeth, zero backlash
Declination worm wheel       934;216mm, 360 teeth, zero backlash
Worm       934;26mm
Right Ascension axle       934;80mm, steel
Declination axle       934;80mm, steel
Right Ascension bearings       934;125mm
Declination bearings       934;125mm
Counterweight shaft       934;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° 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

* These are only guidelines. Some telescopes are very long or very big for their weight and may require a larger mount. Remember also that imaging requirements are more rigid than visual observation.

Average Rating (1 Review):  
Write a Review and share your opinions!

Huge but capable and rich in features
23 April 2020  | 

I'm about 2 weeks in here so these are early comments. I have some heavy Astrophotography gear that over the years has overloaded and worn down my old NEQ6 mount so going for an upgrade I wanted something with a significantly higher load. 52kg is more than enough. I had long considered the EQ8-R as my next mount right until I saw this at the IAS in 2019. Essentially it won the selection battle on having better connectivity, (Serial / USB / WiFi or LAN) built in GPS a significantly lighter "mobile pier" and what appears to be a better cable management system.

Make no mistake this is an observatory class mount, unless like me, you are still fighting the neighbours over light, trees and planning permission in which case it just borders on being portable (when this is allowed again). I have this on the Tri-pier 360 pier base currently which offers a very solid and secure base for the mount. At 26 kg it's not easy to pick up and move but then again it's not designed to be moved regularly.

If like me you are used to Skywatcher Synscan handsets the GoToNova display is a revelation as it displays all the info you need on the panel with no need for scrolling up and down, the menu takes a few days to get used to but is quite intuitive. Plugging into a computer is relatively easy either via the provided serial cable or USB 2 or LAN / WiFI I have not tried LAN yet, I don't have a long enough cable. Disappointingly the WiFi access does not seem to include access through to the USB hub on the cable management system, or if it does I haven't found the right combination of cables yet. The saddle houses the main cable outlets including a 4 port USB2 hub which I can run most of my gear on and a single USB3, which is OK for making a tidy connection to a camera in terms of cables, it could really do with a few more ports here, but It does everything I need it to so this is more of a niggle. The 12V 10A inlet for the power distribution system on the saddle seems to be different plug size to the one used to power the mount, probably a good thing as you don't want a a 10A supply frying the mount electronics.

The saddle is a fixed Losmandy plate and very wide, it is too wide to accept the ADM Vixen Losmandy adaptor ( I was the customer that bought that, don't make my mistake). Because you have to slide plates in it won't take any plate where the fixing bolts protrude from the bottom by more than 1 or 2mm. After several rethinks and a long message exchange with Adam at Rother Valley we adapted a Geoptik Dual clamp type saddle by bolting it to a short plate (for spacing) and a long plate to secure the whole rig to the saddle, this now takes any scope I have easily. Another surprise for me is that in terms of counter weights it balances at pretty much a 1:1 ratio so if like me you have scopes weighing more than 20kg you may need to consider extra counterweights or finding a longer CW bar.

Set-up is little different to other Equatorial mounts and here I would highly recommend the iPolar as it makes polar alignment a breeze if you are setting up from scratch each time. The Ascom controls / guide software is OK but needs work, you can use it to slew to objects on the inbuilt database but the commander software seems to go from a neutral pointing model, where the handset factors your pointing model error from the 3 star alignment process and seems to be more accurate. Guiding so far with a 400mm f5 guidescope is giving some very flat guide graphs so far. Backlash is not zero (it can't be from an engineering perspective) but minimal if compared to other mounts I've used, the magnetic preloading system does an awful lot to help this and is very effective in terms holding the load. The separate shaft lock and gear engagement is also quite unique but also very good, as one who has seen the friction pads on an NEQ6 slip it's a real point in favour of the mount. Still learning it's capabilities but would recommend this mount to anyone looking for a solid observatory class goto system

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4 of 4 people found this review helpful.

Some items that are showing as in stock are in stock at our holding warehouses, not at the shop. To double check the stock levels at the shop, please contact us on 01909774369 or

The delivery times for most items is 1 - 2 days but again, please double check stock levels on important orders before placing an order via the website.

The delivery costs for courier next day are for mainland UK only. If you live in the Scottish Highlands/Islands, Channel Islands or Northern Ireland, then a shipping surchage will apply. please contact us for prices. Smaller items can still go 1st class via Royal Mail.

Please note that if you are wanting to take advantage of our Saturday and Sunday timed services or next day pre 12 or pre 10:30 services, you MUST check that the stock is here at the shop before placing orders. Also, orders using the Saturday and Sunday services must be placed before 1pm the previous working day. Also, please remember to check that the stock is here at the shop before placing orders. If the stock is not at the shop, we won't be able to ship on any of the timed services. 

Please note International customers will need to contact us for a shipping price prior to ordering via the website. We don't ship all items internationally. It is at our discretion what we ship outside of the UK. This all depends on the size and weight of the items. Please get in touch with us for any postage costs. Please note we do NOT ship telescopes or heavy items outside of the UK. This is due to massive postage costs and problems regarding returns.

If you have any questions regarding stock levels or delivery, please get in touch.

Zygo Interferometer Testing For ED Refractor Telescopes!

We are extremely pleased to announce our Zygo Interferometer is now installed and ready for use! Our experienced staff can test refractor lenses up to 120mm aperture and provide a comprehensive 2 page report showing the optical quality and Strehl ratio, plus much more information. We are using the very latest Zygo MX software to provide a more detailed report compared to other standard reports.


The interferometer is essentially a measuring instrument. Within the interferometer is a calibrated laser that is pointed through the optical test surface, then onto a high quality reference sphere, then back through the test subject then to an internal camera which gives us the measurement on the screen. From this, we can adjust the position of the test optic and the reference sphere to obtain a perfectly calibrated system. The more central the laser to the test optic and then on return, the better and more accurate reading and measurement we can take. This takes a lot of adjustment to get the best results from the optical surface. Once the measurement has been taken, we are provided with a series of results that show the optical quality of the surface plus other information. Continue reading for an explanation of the individual values and you can also see a test report that was done on one of our RVO Horizon 60 OTAs. 

We are offering certain telescopes with a Zygo test at an extra cost. Mainly ED doublets and triplets. All available telescopes with a Zygo test report are listed here. Just select Zygo Test Report from the drop down box at the top of the listing and we will test the optics in house and provide a full 2 page report with your scope. This will show you the optical quality of your telescope optics. We can also offer this service on your refractor telescope. Please get in touch for more details about this. 

At Rother Valley Optics, one thing we pride ourselves on is customer service and quality of our equipment. When we test your telescope, we will ensure that it is of the highest quality otherwise, we will reject the scope under our strict quality control and test another model for your peace of mind. One of the main values to look at when testing a refractor is the Strehl ratio. The higher this number, the higher quality lens you have. At Rother Valley Optics, we will guarantee the highest possible Strehl ratio for your telescope.  We will aim to provide 0.95 Strehl or higher on Takahashi, RVO Horizon, William Optics and many more! Generally, the higher the Strehl ratio, the lower the Astigmatism and Coma meaning a better image quality from your instrument. 

Other measurements such as the PV and RMS are important too. With these measurements, the lower the number the better as it shows less curvature on the lens. The flatter an optical lens, the better it will perform. The PV rating (Peak To Valley) is a measurement from the highest point (Peak) to the lowest point (Valley). From this we get the RMS (Root, Mean, Square). This is a similar figure to the PV and measured exactly the same way. The RMS is basically an average height difference from the PV so again, the lower the better. As you can see form the example below, we measured an RMS of just 0.027 wave which is a very good value.

We also measure the Power with our systems which is essentially the error from the reference sphere to the test optic. The reference sphere we use on our system is a very high quality sphere so the closer to zero the Power, the less error between the 2 elements thus ensuring a higher quality optical surface. 

You will also see some more values such as Astigmatism and Coma. Again, these are measured by the interferometer when we take measurements of the optical surface after adjustment. These are values which ideally would be at 0 but as our test optics are all curved lenses, there will always be astigmatism and coma present. The lower the number, the less of these aberations you will effectively see but with most refractors, you can buy field flatteners which will compensate for the coma anyway. The astigmatisms value is explaining the error between the symmetrical curvature of the lens. Basically, no lens will be perfectly symmetrical, the lower the astigmatism, the more symmetrical the lens surface is. 

Once the Zygo test report has been completed, the optical alignment is thoroughly tested and tuned to ensure they are spot on before they leave us. 

All available telescopes are on the website at the link below and ones we've tested already that are available straight away are also listed.

Here is an example of the test what we provide. This was a test on one of our Horizon 60 ED OTA's.

For any questions about this amazing new service, please either call 01909774369 or email


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