Update - September 2019
*** WARNING - REPORTS OF PROBLEMS WITH CEM60-EC MOUNTS ***
It appears that many owners of CEM60-EC mounts are now reporting problems, in particular difficulty guiding the mount satisfactorily. I’ve also been having problems with RA guiding on my previously reliable mount after upgrading the firmware. Most of my clear sky time has been spent getting to grips with a new CEM40 that I bought earlier this year so I haven’t yet been able to definitively diagnose the problem with my mount.
However, I would strongly advise checking out Cloudy Nights and other astronomy fora before committing to a purchase of the EC version of the mount just now.
I also, sadly, have to report that my most recent experience of dealing with iOptron support (due a problem with the first CEM40 that was shipped to me) was nowhere near as positive as my interactions with them when I first purchased my CEM60. The retailer ended up replacing the mount in the end but iOptron were slow to respond and not that helpful when they did so on that back of that I be giving them 3 out of 10 stars today which is a real shame…
Update - March 2019
The CEM60 is now pretty well established and there are plenty of astronomers across the globe using the mount very successfully for both observational astronomy and astrophotography. I got several images published in Sky and Night Magazine and Astronomy Now using the mount. I still get pretty regular contact from prospective buyers (which I always welcome) asking if my views on the mount have changed. Well they have a bit… I’m even more impressed with it! The performance of my mount got better and better with each firmware release and the performance of the encoder is very impressive - to be honest it was only when I started using SharpCap to achieve a more accurate polar alignment that I really realised how impressive.
I am also told that iOptron have upgraded the finish on the mount and there have been a couple of other upgrades too and yet since I first posted this review in 2014 the price in the UK has come down from £2,299 to £1,599 for the standard version and from £3,599 to £2,599 for the EC version - a whole grand cheaper than 5 years ago. I have to say at that price I think both versions of the mount are absolutely outstanding value.
I’ll leave my original review here for those that are interested but suffice to say I remain delighted with my CEM60-EC and I highly recommend it as a fantastic mount for its price range.
This is my review of the iOptron CEM60 centre-balanced mount. The mount comes in two variants: a standard version that supports permanent periodic error correction, and an EC version that has a high resolution encoder on the RA axis to perform real-time error correction. I have the EC version. I am trying hard to give an honest review so my intention is to cover the good, the bad, and the ugly for this mount. This is always tough when you own a mount as bias and emotion have a part to play (shelling out a few grand on something does make you want it to be good), so I accept no responsibility for actions resulting from this review; it’s just my personal opinion. I also have to comment that I have been enormously impressed with iOptron in every way and including the contact that I have had with their customer support so I confess that I am favourably disposed towards the company.
That said, my overwhelming loyalty is to my fellow amateur astronomers, so here we go.
Ease of set up: 8/10
Customer service: 10/10
The CEM60 ships in two boxes, one containing a 21lb (9.5kg) counterweight and the other the mount itself which is shipped in a sturdy flight case. Also included in the box:
Note that like many intermediate and high-end mounts the CEM60 does not ship with a tripod. Suitable tripods, portable piers, and pier adapters are available but I chose to have an adapter made (image to the right) so that I could install the mount on a Celestron CGE Pro / CGEM DX tripod that I already had. The mount requires a platform at least 150mm in diameter with two M8 threaded holes each 65mm from the centre of the platform (i.e. the M8 threads are 130mm centre-to-centre). A 12mm diameter centre stud provides a pivot point when making Az adjustments (my setup uses the tripod’s threaded centre support rod for this purpose).
The CEM60 is an innovative mount design. An evolution of the English Cross Axis, it places the payload closer to the centre of gravity thus giving a better mount to payload capacity than, for example, the more common German Equatorial. iOptron claim a payload capacity of 60lbs (27kg) for visual use. My heaviest imaging rig, a Celestron EdgeHD 1100 with focal reducer, OAG and imaging gear, weights in at around 38lbs (17kg) and it handles this easily.
The mount is manufactured in China and it is reported that quality control has been much higher than is typical for mass-produced telescope mounts. It’s packed with features. The dual saddle plate accepts either Losmandy or Vixen style dovetail bars, an illuminated polar scope is included as standard as is a GPS module which achieves satellite lock remarkably quickly (often in around a minute for me, but it can be up to several minutes) and the mount will also perform an automatic meridian flip.
Another innovative feature is the CEM60’s magnetic gear switches. These act as the clutches on both axes and also serve to hold the worm and ring gear together. The effect is similar to a spring-loaded worm and the result is that backlash is all but eliminated to the extent that it is only just detectable even at a focal length of 2800mm… and this without needing to adjust the worm/ring mesh at all. This is impressive.
A feature I really like is the inclusion of a cable management panel just below the saddle plate. The panel offers 4 x USB 2.0 sockets, 2 x 12v (2.1mm) power sockets and a 6p6c port which can be used to bridge the mount’s ST-4 guide port. This is really useful for the imager as it reduces the chance of cables snagging and makes cable management easier and neater. The inputs for the cable management panel are located next to the polar scope and here the grumbling begins… In order to use the input sockets the metal polar scope cover must remain removed, exposing the eyepiece end of the polar scope to the elements which seems a shame. Also the input for the 6p6c port is on the other side of the mount to the ST-4 guide port. In fairness these are very minor gripes. Of more significance is that the thread on the 12v input socket (which, by the way, is for a 2.5mm x 5.5mm plug) is not long enough to use a lock ring plug and - as the RA axis rotates and with it the input ports - I found that the power cable is prone to fall out. I have managed to address this to my satisfaction, but in my view a simple and inexpensive fix is needed by iOptron to make the connection more secure. Others have also commented that it is a shame that the USB hub on the cable management panel is not powered. This has not been an issue for me personally but given there are USB ports and 12v power in close proximity one has to ask why not?
By the way, the input power socket for the mount (this one is for a 2.1mm plug) suffers the same problem of not having a deep enough thread for use with a lock ring connector but because this part of the mount doesn’t move it is slightly less of an issue. Again, though, I think it would help if the power cable could be secured.
The mechanical parts of the mount appear very well engineered - the azimuth and altitude adjusters used to set polar alignment are a case in point as is the saddle which features spring-loaded dual thumb knobs. An issue for some will be the standard of finish though. While the metal knobs are very attractive, the mount head is made from cast parts and casting marks are visible. The paint job on my mount is acceptable but does seem prone to chipping. The standard of finish might be of concern to some given the cost of the mount, but in all honesty I would prefer time and money to be saved on the paint job rather than on the drive gears.
The CEM60 comes with iOptron’s Go2Nova® 8407+ hand controller. The controller has an 8 line, 21 character per line display and I must say it’s a joy to use. The size of the display makes navigating the menus very easy and the display and hand controller buttons are intuitive. The hand controller also has some nice features including dimmable display and button lighting, a heater to keep the controller dry and functional at low temperatures, and a small LED red light which is just about bright enough to be useful.
The firmware has a similar feature set to Celestron’s NexStar including a polar alignment routine that allows for accurate polar alignment using bright stars other than Polaris, single and muti-star calibration for GoTo alignment and a database of ‘about’ 358,000 celestial objects. Having such an extensive catalogue of objects is probably more of a marketing poly than anything else, but the ease of menu navigation and the ability to find objects using different catalogues (including, for example, Caldwell, Abell, and Herschel) makes selecting a target really easy.
A major downside for me at present is that there is no firmware option to operate the mount with the saddle rotated by 90 degrees to use two telescopes in a side-by-side configuration. iOptron’s suggestion is to remove the saddle and rotate it physically by 90 degrees. This is achieved easily enough by removing four hex bolts, but I switch configurations often enough to prefer an option to do this automatically in software.
iOptron continue to work on refining the firmware for the mount circuit boards and the hand controller. Upgrading the firmware is done using software available from the iOptron website and is relatively straightforward so long as the instructions are followed closely. The hand controller firmware is updated by connecting the handset to a computer using the supplied serial cable but you will need an RS232 serial to USB adapter if your computer doesn’t have an RS232 port. The mount firmware (separate updates for the main, RA, and DEC boards) requires you to plug the serial cable directly into the mount.
Computer control is straightforward using the supplied serial cable (again a serial to USB converter will be required if you computer does not have an RS232 interface). The serial cable plugs directly into the mount and uses the iOptron ASCOM driver (at the time of writing the current version is iOptron Telescope .NET ASCOM Driver 2.6, using the ASCOM 6.1 environment). Once this was installed I was immediately able to control the mount using Stellarium and Cartes du Ciel.
One area where the CEM60 really scores is it’s portability. It’s not exactly a ‘grab and go’ mount but weighing in at 27lbs (12.3kg) makes it eminently transportable and it’s very tough to beat its payload capacity to weight ratio. I really notice the difference in weight between the CEM60 and my CGEM DX (which is 41lbs / 19kg) and the iOptron is more compact too.
Set-up is straightforward if you are familiar with a GoTo German Equatorial Mount as the principles are the same: roughly level and align the mount north, set location, date and time, accurately polar align, and calibrate the GoTo system.
The built-in GPS system sets time and location for you, but this can be set manually too should the GPS fail for any reason. The supplied illuminated polar scope offers a increased level of accuracy over other polar scopes that I have used and the hand controller gives a graphical display of the position of Polaris relative to the Northern Celestial Pole for your location and time.
To refine polar alignment, iOptron have included two firmware routines that allow you to polar align using two bright stars. These routines are similar to Celestron’s All Star Polar Align but, it has to be said, not as convenient as the choice of stars is more limited. The results are excellent though.
Azimuth adjustments are made by two adjuster bolts that work against the two studs that secure the mount head to the tripod / pier. It’s incredibly easy to make precise adjustments. Adjustment in altitude is via a worm gear which again works very well, though the pitch of the gear is quite course making it more difficult - but not impossible - to make fine adjustments. Both sets of adjusters can then be locked down using special cap nuts and this too works very well, though I do find it useful to make the final adjustment with the bolts almost tight.
Once polar aligned there is a choice of alignment routines to calibrate the mount’s GoTo functionality. It’s possible to calibrate on a solar system object or one or more stars. Surprisingly (to me at least) I have found the one star polar align to be adequate: so long as the alignment star used is in the same half of the sky, GoTos reliably place the target on the camera sensor at 2000mm focal length, albeit not always perfectly centred.
There has been much discussion on astronomy fora regarding the efficacy of the high resolution encoders on the EC version of the mount. It is suggested that the iOptron implementation suffers from sub-divisional error (SDE; a type of interpolation error) that limits the practical use of the encoder. To be honest, all I am interested in is getting nice round stars in my astro-photos and so far I’ve had to autoguide in order to achieve that (though not necessarily because of the encoder). This does mean that my imaging runs have effectively disabled the high resolution encoder (a hand controller setting allows you to enable RA guiding which disables the encoder for approximately three seconds after each guide command) so at present I don’t have much to add to the debate.
It’s probably a mistake to get too excited by the PE graph that comes supplied with the mount as this shows the error recorded at the encoder and there may be other issues to contend with in the real world.
What I can say is that I have managed good results at both 2800mm and 1960mm focal lengths (and note that since I use an OAG I am actually guiding at those focal lengths). PHD2 reports a typical RMS of ~0.5 on each axis at an image scale of 0.59” per pixel. The results have been far more impressive than I ever achieved with my CGEM DX despite a DIY hypertune and lots of fettling.
The image to the right shows a crop of the star field around M101 captured with an EdgeHD 11” with 0.7 focal reducer (focal length 1960 mm) and an Atik 460ex mono camera binned 2x2 yielding a resolution of 0.96” per pixel. The field of view for the image is 3 x 2.9 arcminutes and there has been no deconvolution or star shaping. The processed image of M101 in its entirety, more or less, is at the bottom of this page.
In my view the only real competition at this price point is the Avalon LineAR fast reverse mount. The Avalon has greater Periodic Error but its belt drive system means the PE is smooth and slow and thus easily guided out. (EDIT: Note that the Avalon LineAR is entirely belt driven where as the iOptron mounts have belt driven worm gear). Other mounts to consider at similar price points are the Skywatcher EQ8 Pro and (at a stretch as it is almost twice the price) the Mesu-Mount 200.
This is a very capable mount at this price point and comes laden with features that, whether for visual or photographic use, will make your life easier. I am impressed with the mount and doubly-so by iOptron who have a mould breaking attitude to customer service and quality control as far as mass produced telescope mounts go.
I would go so far as to say that the standard version of the mount is peerless at its price point in terms of performance and features. The situation with the high precision encoder version is less clear cut at present. There seems little point in investing in the EC version if you autoguide anyway, as I do; the encoder doesn’t make your autoguiding any better (at least not with the current firmware) and so the Avalon LineAR may be a better bet. As things stand it is a question I continue to ask myself but I am happy with my choice and if the encoder issues can be resolved then that choice will have been vindicated as far as I am concerned.
I hope that you have found this review useful. If you have any questions or comments then please drop me a line.