The CEM70EC starts with the same idea as the standard CEM70: give a serious imaging system substantially more room to grow without moving all the way to the size and weight of an observatory-class CEM120.
It carries up to 70 lb (31.8 kg) of telescope and imaging equipment, excluding counterweights, on a mount head that weighs 30 lb (13.6 kg). That gives it enough capacity for larger SCTs, substantial refractors, Ritchey-Chrétiens, and more complex imaging trains while keeping the head manageable enough to move when the system does not live permanently on a pier.
The difference is the encoder. The CEM70EC adds a high-precision encoder on the right-ascension axis and uses iOptron's Real-Time Periodic Error Correction to continuously monitor and correct the repeating tracking error of the RA drive. iOptron specifies encoder-corrected periodic error below 0.3 arcsecond RMS, measured on the bench over the mount's 348-second worm period.
That makes the CEM70EC particularly attractive for imagers working at longer focal lengths or smaller image scales who want the mount itself to handle the repeating RA worm error before the autoguider ever sees it.
Key Features
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70 lb payload capacity. iOptron rates the CEM70EC for up to 31.8 kg (70 lb) of telescope and imaging equipment, excluding counterweights.
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30 lb mount head. A relatively manageable head for a mount in this payload class.
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Center-Balanced Equatorial design. iOptron's CEM layout places more of the combined mount and payload mass directly over the tripod or pier.
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High-precision RA encoder. Direct encoder feedback monitors the right-ascension axis while the mount tracks.
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Real-Time Periodic Error Correction. The EC version corrects the repeating RA worm error continuously rather than relying on a previously recorded PPEC curve.
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Encoder-corrected PE below 0.3 arcsecond RMS. iOptron specifies this performance over the mount's 348-second worm period under bench measurement.
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Internal iPolar electronic polar scope. The polar-alignment camera is installed in the RA axis and uses plate solving rather than requiring you to position Polaris on a traditional reticle.
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151mm worm wheels on both axes. RA and DEC each use a 248-tooth worm wheel driven by a 21.2mm worm.
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55mm steel axles and 80mm bearings. Substantial mechanical components support the CEM70's larger payload class.
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Precision stepper motors. 128 micro-steps provide a specified motor resolution of 0.07 arcsecond.
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Up to 3.75°/sec slewing. Maximum GoTo speed is approximately 900× sidereal.
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Go2Nova 8410 hand controller. Provides an 8-line × 21-character display and iOptron's extensive GoTo database.
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Built-in 32-channel GPS. Supplies UTC time and location information to the mount.
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Automatic zero-position search. The mount can electronically locate its mechanical reference position.
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Configurable meridian treatment. The mount can stop or automatically flip, with settings allowing up to 10° of travel past the meridian when clearance permits.
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8-inch spring-loaded dual saddle. Accepts both Losmandy D and Vixen-style dovetail plates.
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Through-mount cable management. Power and USB connections are available near the saddle so fewer cables have to cross the moving axes.
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Hard carrying case included. Protects the 30 lb mount head during storage and transport.
- Two-year limited warranty.
What the RA Encoder Changes
A conventional worm-driven equatorial mount has periodic error because small imperfections in the worm and wheel repeat as the worm turns. On the standard CEM70, Permanent Periodic Error Correction and an autoguider are used to reduce that repeating error.
The CEM70EC approaches the RA drive differently.
A high-precision encoder monitors the right-ascension axis while the mount is tracking. The control system uses that positional feedback for Real-Time Periodic Error Correction, continuously correcting the repeating RA worm error rather than depending on a previously recorded correction curve.
iOptron specifies the result as less than 0.3 arcsecond RMS periodic error, measured with the encoder over one 348-second worm period.
That does not mean every imaging system will automatically deliver 0.3-arcsecond stars or 0.3-arcsecond guiding. The encoder is correcting the RA drive inside the mount. Seeing, polar alignment, atmospheric refraction, telescope flexure, wind, balance, guiding, and the rest of the imaging system still exist outside that correction loop.
What the encoder does is remove much of the predictable repeating RA worm error from that list.
Do You Still Guide the CEM70EC?
For demanding long-exposure astrophotography, especially at longer focal lengths, guiding remains a normal part of the imaging system.
The RA encoder should not be thought of as a replacement for every correction a guider can make. It addresses the mount's repeating right-ascension drive error. A guider can still respond to other movement seen through the actual telescope system.
The practical advantage is that the guider no longer has to spend as much of its effort correcting the worm's periodic component. The mount handles that internally through the RA encoder and RPEC system.
We would not choose the CEM70EC simply because you want to stop guiding altogether. We would choose it because you want the mount itself to provide substantially tighter RA tracking before guiding and the rest of the imaging system are taken into account.
RA Encoder, Not Dual Encoders
The CEM70EC has a high-precision encoder on the right-ascension axis.
That distinction matters. The published sub-0.3-arcsecond RMS periodic-error specification refers to encoder-corrected RA tracking. The CEM70EC is not a dual-encoder mount with equivalent high-resolution encoder feedback on both axes.
If your application specifically calls for high-resolution encoders on both RA and DEC, the CEM70EC2 is the model designed for that role.
Room for the Complete Imaging System
The value of a 70 lb payload rating is not necessarily putting a 70 lb optical tube on the saddle. It is having room for the complete telescope system.
A C11, large refractor, Ritchey-Chrétien, or similar telescope can gain considerable weight once the camera, filter wheel, focuser, rotator, reducer or corrector, off-axis guider, dew equipment, rings, dovetails, and cabling are installed. A side-by-side configuration adds still more.
The CEM70EC gives those systems room to grow without treating every accessory as the last few pounds the mount can tolerate.
Payload weight is still only one part of mount selection. A compact telescope and a long telescope at the same weight do not place the same mechanical load on the axes. Tube length, diameter, center of gravity, wind exposure, focal length, and image scale all matter along with total weight.
iPolar Built Into the RA Axis
The CEM70EC includes iOptron's iPolar electronic polar scope inside the mount.
Instead of looking through a traditional optical polar scope, you connect the iPolar to a supported computer and let the software plate-solve the surrounding polar star field. It determines where the RA axis is pointing relative to the true celestial pole and then shows you how to adjust the mount's altitude and azimuth controls.
The pole star itself does not have to be visible. The camera still needs enough of the surrounding polar sky to solve successfully, but you do not have to identify Polaris or Sigma Octantis and place it on a reticle manually.
That is especially useful with an encoder mount because the tracking system can only work from the mechanical alignment it is given. A good polar alignment provides the proper starting point for the rest of the system.
Built for an Imaging Train
As imaging systems get larger, cable management becomes part of the mount rather than an afterthought.
The CEM70EC routes useful power and data connections through the mount to the telescope side. The cable-management system includes two 12V DC outputs rated to 3A, three USB 2.0 ports, DC input and output, iOptron's iPort connection, and a USB input serving the mount's internal connections and hub.
That gives cameras and accessories connection points near the saddle instead of requiring every power and data cable to hang from the telescope and cross the moving RA and DEC axes.
This CEM70EC version uses USB 2.0 and does not include built-in Wi-Fi. If you want the same RA encoder system with USB 3.0 and built-in Wi-Fi, the CEM70ECW is the corresponding version.
Transportable Without Being a Small Mount
A 30 lb mount head is not grab-and-go, but it is still a very different proposition from a CEM120-class mount head approaching 60 pounds before counterweights or telescope are added.
The CEM70EC can live on a backyard or observatory pier and still be moved when you want to take a larger imaging system somewhere darker. The included hard case protects the head during storage and transportation, and the mount separates from the tripod and counterweights into manageable components.
A complete CEM70EC system with a large optical tube is still substantial equipment. We would describe it as transportable rather than lightweight. The important point is that choosing encoder-corrected tracking and a 70 lb payload does not automatically mean the mount has to remain permanently installed.
Tripod or Pier
The tripod or pier is sold separately.
iOptron lists the LiteRoc #8023ACC as a matched tripod for the CEM70 family. A substantial permanent pier is also a natural choice for heavier telescopes, longer focal lengths, or an imaging system that does not need to travel.
With a mount capable of carrying 70 lb of telescope equipment, the support underneath it is part of the imaging system. Choose the tripod or pier for the complete installed payload rather than the mount head alone.
Counterweights
The CEM70EC includes one 20 lb (9.5 kg) counterweight and a 28mm × 415mm stainless-steel counterweight shaft.
One counterweight is enough for many moderate telescope configurations, but heavier systems can require additional counterweight to achieve proper RA balance. The amount needed depends on the complete payload and its center of gravity.
Additional compatible 28mm counterweights are sold separately.
What's Included
- 1x iOptron CEM70EC Center-Balanced Equatorial mount head
- High-precision RA encoder with Real-Time Periodic Error Correction
- 1x Internal iPolar electronic polar scope
- 1x 8-inch spring-loaded Losmandy D / Vixen dual saddle
- 1x Go2Nova 8410 hand controller
- 1x 28mm × 415mm stainless-steel counterweight shaft
- 1x 20 lb (9.5 kg) counterweight
- 1x Hard carrying case
- 1x 12V/5A AC adapter for indoor use
- Mount connection accessories
Not included: tripod or pier, additional counterweights.
Frequently Asked Questions
How much can the CEM70EC carry?
iOptron rates the mount for up to 70 lb (31.8 kg) of payload, excluding counterweights. Telescope length, diameter, center of gravity, focal length, and imaging requirements should be considered along with total weight.
How much does the mount head weigh?
The CEM70EC mount head weighs 30 lb (13.6 kg).
What is the difference between the CEM70 and CEM70EC?
They share the same basic CEM70 mechanical platform and 70 lb payload rating. The standard CEM70 uses conventional worm tracking with Permanent Periodic Error Correction. The CEM70EC adds a high-precision RA encoder and Real-Time Periodic Error Correction, with iOptron specifying encoder-corrected periodic error below 0.3 arcsecond RMS.
Where is the encoder?
The high-precision tracking encoder is on the right-ascension axis.
What is the periodic-error specification?
iOptron specifies encoder-corrected PE below 0.3 arcsecond RMS, measured on the bench over the mount's 348-second worm period.
Does the CEM70EC use PEC?
It uses iOptron's Real-Time Periodic Error Correction, or RPEC, in conjunction with the high-precision RA encoder. It does not rely on the conventional trained PPEC system used by the standard CEM70.
Can I image unguided with the CEM70EC?
The RA encoder can make unguided imaging more practical in some combinations of focal length, image scale, exposure time, and polar alignment, but it does not correct every source of image motion. For demanding long-exposure imaging, particularly at longer focal lengths, guiding remains a normal and useful part of the system.
Does the RA encoder correct polar-alignment error?
No. The encoder corrects the mount's RA tracking and periodic-error behavior. It does not physically correct a misaligned polar axis, atmospheric refraction, telescope flexure, seeing, or wind.
Does the CEM70EC include iPolar?
Yes. iOptron's internal iPolar electronic polar scope is installed in the RA axis.
Does iPolar require Polaris to be visible?
No. Polaris itself does not have to be visible. The camera still requires enough surrounding polar sky for its plate solve to succeed.
Does this version have Wi-Fi?
No. This CEM70EC uses USB 2.0 for computer communication. The CEM70ECW adds built-in Wi-Fi and USB 3.0.
Does this version have USB 3.0?
No. Its through-mount USB hub is USB 2.0. Choose the CEM70ECW if USB 3.0 through the mount is important to your imaging system.
How many counterweights are included?
One 20 lb (9.5 kg) counterweight is included. Heavier telescope systems may require one or more additional counterweights.
What dovetail plates fit the saddle?
The 8-inch spring-loaded dual saddle accepts both Losmandy D and Vixen-style dovetail plates.
What power does the CEM70EC require?
The mount uses 12V DC at up to 5A with a 5.5mm/2.5mm connector. iOptron lists typical consumption at approximately 0.6A while tracking and 0.8A during GoTo. A 12V/5A AC adapter intended for indoor use is included.
What tripod should I use?
iOptron lists the LiteRoc #8023ACC as a matched tripod for the CEM70 family. A pier is also an excellent choice for heavier or permanent imaging installations.
CEM70EC or CEM70EC2?
The CEM70EC uses a high-precision encoder on RA. The CEM70EC2 adds high-precision encoder feedback on both RA and DEC. If your primary goal is encoder-corrected periodic error during tracking, the CEM70EC provides that on the axis where periodic error matters. Choose the EC2 when your application specifically benefits from high-resolution positional feedback on both axes.
Final Thoughts
The CEM70EC is not simply a standard CEM70 with a higher specification on the box. Its high-precision RA encoder changes the way the mount handles the repeating tracking error produced by the worm drive.
The underlying platform still provides the reasons to choose a CEM70 in the first place: a 70 lb payload on a 30 lb head, internal iPolar, through-mount cabling, GPS, automatic zero search, a substantial dual saddle, and enough portability to move the system when necessary.
The EC version adds encoder feedback and Real-Time Periodic Error Correction to that platform. If you are working at longer focal lengths, smaller image scales, or simply want the RA drive itself to handle periodic error before the guider has to respond to it, that is the reason to choose the CEM70EC.
