Dear All,


After years of using my Skywatcher NEQ6, I ​​am ready for a new mount. I have my eye on the iOptron CEM40EC.



My goal is not to start a whole discussion on this forum about which mount would be the right choice.
But I would like to know your experiences with this mount and its use with EKOS/INDI?

And if there is a clear reason not to choose this mount, I would appreciate it if someone would let me know, if necessary via a private message.


Thanks before hand...

Is there really no one here who uses this mount?

Likely a lot more users of the non-EC version. A lot would be in common between EC and non-EC, of course. I think there's some consensus that the encoders are not so great as to be worth the extra cost vs the non-EC, which keeps the number of EC users down (but I have no direct experience with the performance of the EC version).

There is (or maybe was?) a weirdness if you use an rPi, in that the CEM40 uses a usb-serial chip that does/did not have the correct driver for rPi. I used a non-powered usb hub in between the pi and the CEM40. I actually still use the hub even after switching to a mini-pc, because I just swapped the pc in. Maybe some day I'll take the hub out

Otherwise, not much in the way of Ekos/SMate issues. If you want to park at the NCP, you need to "find home" then manually slew just a tiny bit off from home and set that as Park, else it is prone to getting confused about where to park.

Performance of mine has been excellent. Consistently guides below 0.5" RMS when loaded with an AT130EDT.

Thank you, that is very useful feedback.

The encoders (actually only on RA) do indeed have a disputed reputation and the more I inform myself, the less convinced I am to include this one. I will certainly take into account your comment about the USB driver and the park position, which will be useful during the first use.

Maybe not quite in the right forum: but what are your findings regarding backlash?

I find essentially no Dec backlash. The other night, just to check, I enabled backlash compensation in PHD2 at the minimum 20ms value. 4 hours of guiding later, PHD2 had not increased the compensation time at all, confirming that there is at most 20ms of backlash. [the Guide Assistant always reports a few hundred milliseconds, but that is based on just a single direction reversal and I have never found it to be even close to reliable]

Thank you again.

Is there a specific reason you use PHD2 in stead of the internal guider?
And I deduce from other messages on this forum that even more people use PHD2.

I use the internal guider sometimes, also. I got into the habit of using PHD2 when I was coming to grips with my first mount. You get a more transparent view into what the guider is doing and all of its settings with PHD2. On the other hand, PHD2 (at least with Ekos, at least for me) has an annoying habit of losing track of the profile and telling me that I need to use the wizard to make a new one. But neither guider has a substantial performance advantage.

Thank you again for the feedback.

This confirms my choice for a new mount.
I have always used internal guider and will continue to do so.

Hi,

No good experience with the CEM40 for me, sorry to say.

I replaced my Skywatcher HEQ5 Pro with a CEM40 (not CE) in May 2021.
It's a great mechanical construction but I've had a lot of USB connection error problems with it.
Since purchase I probably have had no more than 2 nights without trouble.

I've changed internal USB cable, as adviced by iOptron (had to buy it from iOptron!) but no luck.
They also asked me to replace the power supply, so I replaced with a more powerful supply (10 amps instead of the supplied 1.5 amps one).
Again, I had to purchase it. No luck.

I've tried different USB hubs, powered and non-powered. Replaced the external USB cable multiple times.

At one point iOptron suggested me to try the StarFi Wifi module that connects to the HBX port instead of the USB port.
So I purchased one (again...). It worked for controlling the slew, but it turned out you can't use it for guiding correction, which basically makes it useless for astrophotography.
Today I see they have updated their web pages with the text "NOT for CEM40 or GEM45 series mount", which was not there before.

iOptron continously push the problem back to me, also suggesting to use a PC instead of rPI/Stellarmate.
If they were serious I would expect them to send me a replacement mount but it hasn't happened yet.

I had no problem whatsoever with the HEQ5 so I actually kind of regret selling it. I really thought the CEM40 would be an upgrade, but no, not for me at least.
Maybe I've just had bad luck with my mount, but the many wasted photo nights and long mail conversations with iOptron and wasted purchases with no resolution almost have made me lose my interest for the hobby

Would I buy another iOptron? No, sorry to say.

// Åke