iOptron Mounts (CEM120/70) and Voyager


I am in the market for a new mount, the mount will be installed in an observatory and will work unattended. I already have a Paramount MX+ and it is excellent when operated remotely, it never gets lost and never run the telescope into the pier, really nice mount, it also plays very nice with Voyager.

However, I don’t have the funds to get another Paramount. Max budget is 4K USD.

Some requirements:

  • 100% compatible with Voyager
  • 100% remotely operated, no need to physically press a button to initialize the mount.
  • Robust Tracking/Slew limits
  • Ability to recover from power failure or PC crash (unattended initialization?)
  • Photographic weight capacity ~45lbs (could be more, portability is not an issue since it will be installed in an observatory) I will mount a RASA11
  • Minimal periodic mechanical adjustments, I don’t mind tunning the mount every 3 months, but I don’t want to adjust the worm mesh every other week.

Any experience with these mounts? How do they play with Voyager? Are they suitable for remote unattended operation?

If you have other mount that I should consider please feel free to add it.



I can’t comment directly as I am waiting for my CEM70G to arrive, however I know of one user who has been using Voyager with a CEM60 (Both vanilla and CEM60EC) for some time and another with a CEM60EC, I don’t see any reason to expect the new 70 not to behave itself.

Just for info Voyager work with all mount having Ascom driver in direct way and with all mount supported by theskyx and thesky6.

I’ve got a CEM120EC2 and there’s no issues with it and Voyager at all. I’ve had the mount for about 1.5 years now and have adjusted the mesh once about 9 months ago, I think. I don’t expect to need to adjust it again in the near future.

I’ve got 2 scopes on it - RC10 + Sharpstar 107PH and it’s fine - I think I worked out I was around 30 - 35 kgs on the mount (not including counterweights, of course).

If I was to buy the mount again, I would not bother with the encoder version - do some searches on Cloudy Nights to see why. But the base version would be fine, I think.

It’s possible to get the CEM120 to turn on remotely, since I’ve got a switch on the DC supply to flick on the mount, camera, etc with one action. My dome is in my backyard, so my start up is wander out, turn things on, fire up Voyager, connect in Voyager (this is more a sanity check of Windows than needed for Voyager), run whatever dragscript, go inside for the night, then close down whenever in the morning (or earlier if the weather goes bad). My main reasons for going out to the dome at night to check things is mostly for the weather/clouds (as I currently don’t have automation for that).

I have the CEM60 and it is 100% automated. I don’t even touch power. I control that through my phone. The mount has been wonderful and never an issue. Meridian flips have been a no brainer. The only thing to comment is that Ioptron has the Zero position. To have it work seamlessly with voyager, I went slightly off the zero position and set the park. Since doing that all the park commands will put it back in that same spot and start up is already aligned and ready to go. my rms in phd2 is anywhere from .20 to .30 depending on how well I have polar aligned etc. I’m stretching the weight right now with the Quattro 10 but have had no issues. Still seeing same rms values. I would highly recommend the CEM mounts.


Have you tried the home ?

Yes. It always sends the scope to the traditional point of horizontal to the ground. Once I set the park I didnt have to deal with those options any more

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Is the CEM120 default park/home position different to the CEM60 and new 70? I don’t know when I will get my hands on the CEM70G to confirm it but I understood the factory home position to be counterweight down, pointed at the pole?

The CEM60 and Voyager play wonderfully with each other. Don’t hesitate to get a CEMxxx if any kind. Great mounts!

Thanks everybody for the input. It looks like a CEM120nonEC is a good candidate for my needs.

I appreciate your support and comments.



There’s a low volume forum: if you want to discuss more on the specifics of iOptron mounts.