After many years with the Losmandy G11 mount in my astrophotography adventure, it’s time for a change. The iOptron CEM mounts seem to be rapidly gaining the market, becoming more and more popular in the astrophotographer community. The variety of product lines allows to choose the right model to suit the needs of each user. Anyway, the purchase of this particular model turned out to be a real challenge for me. I could not find any single store in the EU where I couid buy it right away. Usually the waiting time is about 6 months. Certainly, pandemic restrictions influenced to this situation, but the demand and interest from customers site has its strong impact as well. Finally, I found the mount outside the EU in Great Britain in the First Light Optics store https://www.firstlightoptics.com. Contact with the store and support is invaluable, so I give them the highest rating. After paying customs fees, the shipment arrived in two packages – in the first one I received a solid aluminum case with the mount, in the second one there was a counterweight.
The design of the CEM mounts ensures very good stability, rigidity and high load capacity while reducing the weight and size of the head. CEM70EC with a load capacity of 32 kg and an curb weight of 13 kg is perfect for use in permanent observatories as well as away sessions. Contrary to the German mounts (GEM), the right ascension axis has a solid support on the bearings at two points, thanks to which the bearings load is even and the head of the mount in the RA axis moves very smoothly without any resistance at all. Balancing the CEM mount is simple and fun!
So what are the most important features of the CEM mount? Stability and smoothness of guidning, its stiffness, no play and … the satisfaction of the owner 🙂 Below is a screenshot of the PHD2 with the tracking graph. The scale of the graph is +/- 1.5 “and yet the curves are within +/- 0.5”. Total error is 0.27 arcsec, RA axis error 0.2 “and DEC axis 0.19”. For me these are very good results that I have never experienced with the previous mount so far.
However, the first tests of the CEM70EC-NUC were for me … well, I can say a slight disappointment. PHD2 showed a quite big backlash in the declination axis. I did not expect this. My expectations were completely different. I contacted the iOptron manufacturer in the United States from where I received some recommendations. iOptron suggested to loose the worm against the worm wheel as they can be tighteen to much and in consequences can cause the overall system to become excessively stiff. That could be done according to following procedure: https://www.ioptron.com/v/Manuals/C70_CEM70_Manual.pdf However, any chnges in the worm i worm wheel system did not bring about a fundamental change, which suggested that the problem was elsewhere. The experiences of other users, described in various internet forums, turned out to be very helpful. The main reason for the big Backlash was the not enough tension of the drive belt, which you can see in the video I prepared (link at the end of the page).
The CEM70EC-NUC with an optical encoder in the RA axis is a mount with great parameters and performance in its class. It works very well during away sessions due to the relatively low weight (13 kg), quick assembly, precise alignment to the polar star with the use of an electronic polar scope (accuracy 0.15 – 0.5 arc-min). In my opinion, it is a device worth recommending. During the short test I was able to take a photo and check guiding precision. I took only 8 frames for 300 sec each but it was enought to observ how it works. Despite the short exposure time, the IC405 nebula’s subtle structures can be seen in the image.
If you are interested in a more detailed description of the CEM70EC-NUC assembly, I encourage you to watch the movie i prepared. Any questions and comments are warmly welcome.
Clear sky !!!