For many imagers, the useful middle ground is a mount that has enough capacity for a serious telescope and complete imaging train without becoming something you hesitate to carry outside. The iOptron CEM40 is built around that idea.
It carries up to 40 lb (18 kg) of telescope and imaging equipment, excluding counterweights, on a mount head that weighs just 17.4 lb (7.9 kg). That makes it a natural match for imaging refractors, 8-inch SCTs, smaller Ritchey-Chrétiens, and similar systems that need more than an entry-level mount but do not require CEM70-class capacity.
Internal iPolar provides camera-based polar alignment, Permanent Periodic Error Correction helps reduce the repeating component of RA tracking error, GPS supplies time and location information, and automatic zero-position sensing gives the mount a repeatable mechanical reference. A 6-inch dual saddle accepts both Losmandy D and Vixen-style dovetails, while an included hard case protects the head when the system travels.
This C402A version is the mount head package. The tripod or pier and counterweight are selected separately, making it a good choice if you already have a compatible support or want to build the system around a particular tripod or pier.
Key Features
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40 lb payload capacity. iOptron rates the CEM40 for up to 18 kg (40 lb) of telescope and imaging equipment, excluding counterweights.
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17.4 lb mount head. At 7.9 kg, the CEM40 offers considerably more payload capacity than its own weight might suggest.
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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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Internal iPolar electronic polar scope. Camera-based polar alignment eliminates the need to position Polaris on a traditional polar-scope reticle.
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Periodic error below ±7.5 arcseconds. iOptron specifies native PE below ±7.5 arcseconds, measured over the 400-second worm period.
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Permanent Periodic Error Correction. A trained PEC curve can be stored in the mount to reduce the repeating component of RA tracking error.
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Belt-driven worm system. Both axes use 110mm diameter, 216-tooth worm wheels driven by 17mm brass worms through synchronous belts.
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45mm steel axles and 68mm bearings. Substantial internal components for a mount head weighing less than 18 pounds.
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Precision stepper motors. 128 micro-steps provide a specified motor resolution of 0.08 arcsecond.
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Up to 4.5°/sec slewing. Maximum GoTo speed is approximately 1080× sidereal.
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Go2Nova 8410 hand controller. Provides an 8-line × 21-character display, built-in heater, and a database of more than 212,000 objects.
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Built-in 32-channel GPS. Supplies 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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Power-down memory. The mount retains positional information when powered off normally.
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Configurable meridian treatment. The mount can stop or flip, with settings allowing up to 10° of travel past the meridian when clearance permits.
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6-inch dual saddle. Accepts both Losmandy D and Vixen-style dovetail plates.
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Through-mount connections. A 12V DC output rated to 3A, ST-4 guide connection, and USB are routed through the mount.
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Optional Wi-Fi. iOptron's external iStarFi adapter can add wireless mount control.
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Hard carrying case included. Protects the mount head during storage and transportation.
- Two-year limited warranty.
Why the CEM40 Works So Well as an Everyday Imaging Mount
The CEM40 sits in a useful place between small portable equatorial mounts and larger systems such as the CEM70.
An 80mm or 100mm refractor may leave plenty of unused capacity, which gives you room for the camera, filter wheel, focuser, guide equipment, dew control, and other hardware that eventually finds its way onto an imaging system. Move into a larger 115mm or 130mm refractor, an 8-inch SCT, or a compact RC, and the CEM40 still provides a substantial 40 lb payload rating without requiring a 30 lb mount head underneath it.
That matters on ordinary nights. A mount can have excellent specifications and still spend too much time indoors if moving it becomes an event. At 17.4 lb, the CEM40 head is light enough that carrying it outside or loading it into the car remains practical.
Payload weight is only part of choosing a mount, however. A compact telescope and a long refractor at the same weight do not place the same demands on the axes. Tube length, diameter, center of gravity, wind exposure, focal length, and image scale should all be considered along with the number on the scale.
Tracking and Guiding
The standard CEM40 is a precision worm-driven mount rather than an encoder-corrected model.
Both RA and DEC use 110mm diameter, 216-tooth worm wheels driven by 17mm brass worms through synchronous belts. The RA worm completes one cycle every 400 seconds, and iOptron specifies native periodic error below ±7.5 arcseconds.
Permanent Periodic Error Correction allows the mount to store a correction for the repeating component of that RA worm error.
For demanding long-exposure astrophotography, particularly as focal length and image scale increase, conventional autoguiding remains the normal approach. That is not unusual in this class of mount: PPEC handles the predictable periodic component while the guider responds to the behavior of the complete telescope and imaging system.
If you specifically want a high-resolution RA encoder correcting periodic error inside the mount, the CEM40EC is the corresponding step up.
iPolar Built Into the Mount
The CEM40 includes iOptron's iPolar electronic polar scope inside the RA axis.
Instead of looking through an optical polar scope and positioning a star on a reticle, iPolar photographs the surrounding polar sky and plate-solves the field. The software then shows you how to adjust the mount's altitude and azimuth controls to bring the RA axis onto the celestial pole.
Polaris itself does not have to be visible. The camera still needs enough surrounding polar sky for the plate solve to work, but you do not have to identify or manually position the pole star.
For a mount that is likely to travel or be set up repeatedly, having the polar-alignment camera permanently installed in the mount is particularly convenient.
Connections for an Imaging System
The CEM40 includes a simple through-mount cable-management system.
A 12V DC output rated to 3A, an ST-4 guide connection, and USB are routed through the mount so those cables do not have to cross the moving axes externally.
This is not the multi-port USB hub found on some of iOptron's larger or differently equipped mounts. A complex imaging train may still use a small USB hub or mini computer mounted near the telescope.
The mount itself communicates with a computer through USB. Built-in Wi-Fi is not included on this version, but iOptron's optional iStarFi adapter can add wireless mount communication.
Under the Night Sky
The CEM40 is especially well suited to the telescopes many deep-sky imagers use night after night.
With an 80mm to 130mm refractor, it can carry a complete wide-field imaging system for large nebulae, star fields, and extended galaxies. An 8-inch SCT with a reducer moves the system toward smaller galaxies, globular clusters, and planetary nebulae while still remaining within the mount's published payload class.
A compact RC can serve a similar role for imagers who want additional focal length in a relatively short optical tube.
As those systems become longer, heavier, or more sensitive to wind, the mechanical demands increase even when the scale says the payload is still below 40 pounds. If your telescope plans are moving toward significantly larger tubes such as a C11 or a large refractor with a heavy imaging train, the CEM70 offers considerably more room for that growth.
Choose Your Tripod or Pier
This C402A package does not include a tripod or pier.
The matched portable option is iOptron's #7623 LiteRoc tripod, which uses a 120mm top designed for the CEM40, GEM45, HAE43, and HEM44 families.
An iOptron Tri-Pier is another option when additional mass and rigidity are more important than having the lightest possible traveling system. A properly configured permanent pier is a natural choice for a fixed backyard or observatory installation.
Do not confuse the #7623 with the larger #8023ACC LiteRoc used by mounts such as the CEM70, CEM60, and HAE69. They are different tripod platforms.
Counterweight Required
This head-only package also does not include a counterweight.
The CEM40 uses a 28mm diameter stainless-steel counterweight shaft measuring 280mm long. iOptron offers compatible 5 kg (11 lb) and 2.5 kg (5.5 lb) counterweights.
The correct amount of counterweight depends on the complete telescope and imaging train. A lighter refractor may require less counterweight than an SCT or heavier refractor loaded with cameras and accessories.
Adding counterweight does not increase the mount's 40 lb payload rating; its purpose is simply to balance the installed telescope system properly.
What's Included
- 1x iOptron CEM40 Center-Balanced Equatorial mount head
- 1x Internal iPolar electronic polar scope
- 1x 6-inch Losmandy D / Vixen dual saddle
- 1x Go2Nova 8410 hand controller
- 1x 28mm × 280mm stainless-steel counterweight shaft
- 1x Hard carrying case
- 1x 100–240V AC adapter for indoor use
- Mount connection accessories
Not included: tripod or pier, counterweight.
Frequently Asked Questions
How much can the CEM40 carry?
iOptron rates the CEM40 for up to 40 lb (18 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 current C402A CEM40 head weighs 17.4 lb (7.9 kg).
Does this CEM40 include iPolar?
Yes. This C402A version includes iOptron's internal iPolar electronic polar scope.
Does iPolar require Polaris to be visible?
No. Polaris itself does not have to be visible, although enough surrounding polar sky must be available for the camera to plate-solve successfully.
What is the periodic error?
iOptron specifies native periodic error below ±7.5 arcseconds, measured over the mount's 400-second worm period.
Does the CEM40 have PEC?
Yes. The standard CEM40 supports Permanent Periodic Error Correction.
Does the CEM40 need guiding?
For demanding long-exposure astrophotography, particularly at longer focal lengths, guiding is the normal approach. The standard CEM40 does not have the high-resolution RA encoder used by the CEM40EC.
CEM40 or CEM40EC?
Both share the same basic 40 lb mechanical platform. The standard CEM40 uses conventional worm tracking with PPEC. The CEM40EC adds a high-resolution RA encoder with real-time correction of the repeating RA drive error. If you already expect to guide and do not need encoder correction, the standard CEM40 is the less expensive route into the same payload class.
Does this package include a tripod?
No. This is the head-only C402A package. The #7623 LiteRoc is iOptron's matched portable tripod for the CEM40 family, and the Tri-Pier is another option.
Does it include a counterweight?
No. A counterweight is required and sold separately. iOptron offers compatible 5 kg and 2.5 kg counterweights for the CEM40's 28mm shaft.
Can the CEM40 carry an 8-inch SCT for imaging?
An 8-inch SCT and typical imaging equipment can fall comfortably within the CEM40's published 40 lb payload class, but total weight is not the only consideration. Focal length, tube geometry, accessory load, balance, wind, and the image scale you intend to use all affect how demanding the system will be.
Which LiteRoc tripod fits the CEM40?
The CEM40 uses iOptron's #7623 LiteRoc tripod with a 120mm tripod head. The larger #8023ACC LiteRoc is intended for the CEM70, CEM60, HAE69, and iEQ45 families.
Does the CEM40 have built-in Wi-Fi?
No. The mount communicates over USB. iOptron's optional iStarFi adapter can add wireless mount control.
Does it have a built-in USB hub?
No. The mount provides USB as part of its cable-management system, along with a 12V/3A output and ST-4 connection, but it does not provide a multi-port imaging hub.
What power does the CEM40 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 0.9A during GoTo. A 100–240V AC adapter intended for indoor use is included.
Accessories
iOptron #7623 LiteRoc Tripod (sold separately): the matched portable tripod for the CEM40, GEM45, HAE43, and HEM44 families.
iOptron 5 kg #8027 or 2.5 kg #8027-05 Counterweight (sold separately): choose the amount needed to balance your complete telescope and imaging train.
iOptron Tri-Pier #8034 (sold separately): a more substantial support option when portability is less important.
iOptron iStarFi Wi-Fi Adapter (sold separately): adds wireless mount communication to the CEM40.
Final Thoughts
The CEM40 works because it gives an imager meaningful capacity without giving up the part that makes a mount easy to use regularly.
Forty pounds of payload capacity gives refractors, 8-inch SCTs, compact RCs, cameras, focusers, filter wheels, and guiding equipment room to build into a complete system. Internal iPolar, GPS, PPEC, automatic zero search, through-mount connections, and the dual saddle provide the features expected from a modern imaging mount.
Yet the head still weighs only 17.4 pounds and travels in its own hard case.
If your imaging system needs more than a small portable mount but you still want something you will carry outside on an ordinary clear night, that is where the CEM40 makes sense.
