iOptron CEM40-EC Mount GoTo High Precision Encoder with 2″ tripod: precision mount with RA encoder on heavy-duty tripod
The iOptron CEM40 is a centrally-balanced equatorial GoTo mount with a payload capacity of 18 kg (40 lbs) excluding counterweight, at a head weight of only 7.2 kg (15.8 lbs). The weight of the mount and telescope rests directly above the center of the tripod, giving a remarkably quiet and stable setup.
The EC version features a high-resolution encoder on the right-ascent axis that corrects the periodic error in real time to less than 0.25 arcseconds RMS. For short and medium brand point distances, this often allows you to take photos without autoguiding.
The included 2-inch tripod gives this photography set an extra sturdy base.






Real-time error correction on the RA axis
The encoder continuously measures the actual axis movement and makes immediate adjustments. Stars remain sharp in long, unattended exposures without a guiding camera, cables, or extra software.
For maximum precision at long brand point distances, the ST-4 port remains available.

GoTo, GPS, and heated handgrips
The Go2Nova 8407+ hand controller contains a database of over 200,000 objects and has a built-in display heater, so the screen remains readable even in freezing temperatures. The 32-channel GPS in the mount automatically sets the time and position.
Computer control is via USB. Wireless control with SkySafari or ASCOM is possible with the optional iStarFi WiFi module. An ST-4 port is ready for autoguiding.

Accurate and quiet mechanism
Low-consumption stepper motors control both axes. The periodic error remains within plus or minus 7 arcseconds and can be further reduced with recording PPEC.
The dual saddle accommodates Vixen and Losmandy rails, the large geared clutch levers also work with gloves on, and internal cable management keeps the setup tidy.
Included
- CEM40-EC mount head with RA encoder and built-in iPolar
- Go2Nova 8407+ Handheld Controller with Display Heating
- 2 inch tripod
- 4.5 kg counterweight with counterweight tongs
- Network adapter and USB cable
Featured accessories
Add the iStarFi WiFi module for wireless control and the 15cm MiniPier for clearance around the zenith.
For whom yes and for whom no
- ✓ Astrophotographers who want to take long exposures without autoguiding
- ✓ Who is looking for maximum tracking accuracy up to 18 kg
- ✗ Pure visual observers: the standard CEM40 will suffice then
Specifications
| Type | Center-balanced equatorial GoTo mount |
| Carrying capacity | 18 kg (40 lbs), excluding counterweight |
| Head of weight | 7.2 kg (15.8 lbs) |
| Error correction | Real-time via RA encoder, less than 0.25 arcsecond RMS |
| Manual | Go2Nova 8407+ with display heating, over 200,000 objects |
| Pole finder | iPolar electronic, built-in |
| GPS | Built-in, 32 channel |
| WiFi | Optional via iStarFi module |
| Saddle | Double, Vixen, and Losmandy |
| Connections | USB, ST-4 autoguiding, cable management |
| Counterweight | 4.5 kg |
| Nutrition | 12 V DC |
| Tripod | 2 inch, included |
You can find more mounts and accessories for this merk at the iOptron merk page.





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