Not every observer wants a laptop beside the telescope. There's a lot to be said for carrying a scope into the backyard, aligning it on Polaris, and spending the evening looking at the sky rather than a computer screen. The iOptron CEM26 with AccuAlign was made for just that kind of observing, although it has considerably more capability tucked away inside its compact housing than its traditional optical polar scope might suggest.
The CEM26 mount head weighs only 10 pounds (4.5 kg), yet iOptron rates it to carry up to 26 pounds (12 kg) of telescope and accessories, not including the counterweight. This unusually high payload-to-mount-weight ratio comes from iOptron's center-balanced equatorial design, which places the combined weight of the telescope and mount more directly over the center of the tripod. Rather than hanging most of the load off to one side, as in a conventional German equatorial mount, the CEM26 uses its geometry to help provide a stable platform without requiring an unnecessarily heavy mount head.
This particular C261B3 package combines the CEM26 with an illuminated AccuAlign optical polar scope and iOptron's heavier 1.75" LiteRoc stainless steel tripod. You get the convenience of computerized GoTo and automatic tracking, the simplicity of traditional polar alignment, and a more substantial tripod beneath your telescope. It's a combination that makes good sense for someone who observes primarily from the backyard but occasionally wants to pack everything into the car for a trip to darker skies.
Polar Alignment the Traditional Way
Before an equatorial mount can accurately follow the stars, its right ascension axis must be aligned parallel to the Earth's rotational axis. This is called polar alignment. Once aligned, the mount can compensate for the rotation of the Earth by turning its right ascension axis at the same rate the stars appear to move across the sky.
The CEM26's AccuAlign optical polar scope makes this a relatively simple operation. The polar scope is built into the mount's right ascension axis and has an illuminated reticle marked with a series of circles and reference positions. After entering your location, date, and time into the Go2Nova hand controller, you can display the correct position of Polaris on the reticle. Adjust the mount's altitude and azimuth controls to place Polaris where the controller indicates, and your basic polar alignment is complete.
Why not simply put Polaris in the center? Because Polaris isn't exactly at the north celestial pole. It's approximately three-quarters of a degree away. That may not sound like much, but an equatorial mount pointed directly at Polaris instead of the true pole will slowly develop tracking errors as the Earth rotates. AccuAlign accounts for that offset, giving you a more accurate starting alignment.
One particularly useful feature of the CEM26's mechanical design is that the declination shaft never blocks the optical polar scope. On some equatorial mounts, you have to rotate the telescope or declination axis to see through the polar finder. With the CEM26, the view remains unobstructed, making polar alignment and subsequent checks much more convenient.
If Polaris is hidden behind a tree, house, or other obstruction, iOptron's Polar Iterate Align routine offers an alternative using two suitably positioned bright stars. The procedure uses the hand controller and the mount's mechanical adjustments to refine the alignment through successive iterations. For ordinary visual observing this can be quite useful, while demanding long-exposure photography may benefit from a more precise alignment check afterward.
The CEM26 is also available with iOptron's iPolar electronic polar scope, which uses a small camera and computer software to perform the alignment. The C261A3 package combines iPolar with the same LiteRoc tripod supplied here. Either version uses the same basic CEM26 mount, so the decision is largely a matter of how you prefer to polar align. If you already know your way around an optical polar finder, or simply don't want to involve a computer, AccuAlign is a very reasonable choice.
A Ten-Pound Mount with the Mechanics of a Larger Equatorial
The CEM26 may be small, but it isn't simply an oversized star tracker. Both the right ascension and declination axes have 3.46" (88mm) diameter aluminum worm wheels with 144 teeth, driven by 0.60" (15.2mm) brass worms through synchronous belt transmissions. The 1.38" (35mm) diameter steel axis shafts turn on 2.17" (55mm) ball bearings, providing support for the telescope as it moves to different parts of the sky.
The worm gears are responsible for the very small, controlled movements required to track celestial objects. A belt transmission connects the motors to the worms without the additional meshing gear stages used in some mounts, helping keep the drive system mechanically straightforward. The large bearings and steel shafts support the load as the telescope changes orientation, while the center-balanced arrangement places that load in a more favorable position over the tripod.
iOptron specifies periodic error of less than ±12 arcseconds over the mount's 600-second worm period, based on the manufacturer's bench test. Periodic error is the small, repeating tracking variation caused by imperfections in the worm and wheel. The CEM26 includes Permanent Periodic Error Correction (PPEC), which allows the mount to record corrections for the repeatable portion of that error and retain them for future observing sessions.
For long-exposure astrophotography, the CEM26 also has an ST-4-compatible autoguider port and USB computer control through ASCOM. With a suitable guide camera monitoring a reference star, the mount can make small corrections during an exposure to compensate for tracking errors. This is particularly helpful when photographing faint galaxies and nebulae, where individual exposures may last several minutes. The standard CEM26 does not include the high-precision right ascension encoder found in the more expensive CEM26EC, so autoguiding is advisable for demanding deep-sky imaging.
Both axes have large quick-lock gear engagement switches that allow the telescope to be balanced before observing. The spring-loaded drive system and positive-lock mechanism are designed to be easy to operate, even while wearing gloves. As with any precision worm-drive mount, the telescope should be supported when disengaging the gears, and the gear switches should be operated according to iOptron's instructions.
The CEM26 has a 3.8" adjustable Vixen-style dovetail saddle. It accepts standard Vixen-format mounting plates, but not the wider Losmandy D-style dovetails. Although the mount is rated for a 26-pound payload, tube length and diameter matter as well as weight. iOptron recommends optical tubes smaller than 6" in diameter. Compact refractors, small Maksutovs, camera lenses, and appropriately sized imaging systems are natural partners for the CEM26.
The LiteRoc Tripod Makes a Difference
A mount can have excellent gears and electronics, but those advantages don't help much if the tripod allows the telescope to shake every time you touch the focuser.
The C261B3 includes iOptron's heavier 1.75" LiteRoc stainless steel tripod rather than the lighter 1.5" tripod offered with some other CEM26 packages. The LiteRoc weighs approximately 16.5 pounds (7.5 kg), considerably more than the 10-pound mount head. The heavier legs and metal spreader provide a more substantial foundation, helping resist vibration when focusing or observing in a light breeze.
This arrangement also makes the CEM26 convenient to transport. You can carry the mount head, tripod, counterweight, and telescope as separate pieces rather than wrestling with a heavy assembled equatorial mount. At a dark sky site, particularly after a long drive, being able to unload everything without needing another pair of hands is a welcome advantage.
For someone trying to assemble the absolute lightest possible travel system, the smaller 1.5" tripod saves some weight. However, if you're using a longer refractor, a complete astrophotography setup, or simply appreciate a firmer foundation under your equipment, the LiteRoc is well worth considering.
Computerized GoTo Without the Computer
The supplied Go2Nova 8409 hand controller contains a database of approximately 212,000 astronomical objects, including the Messier, NGC, IC, and Caldwell catalogs, along with stars, planets, and many other celestial targets. After polar alignment and the appropriate GoTo alignment procedure, select an object from the controller and the CEM26 slews to it automatically.
Nine selectable slew speeds let you move from rapid repositioning across the sky to fine adjustments when centering an object at high magnification. The mount can slew at up to 6 degrees per second and provides sidereal tracking to keep celestial objects centered once they're found.
Built-in Wi-Fi and USB computer control are available if you later decide to operate the mount from planetarium software or an astrophotography computer. Wi-Fi controls the mount itself; it isn't a wireless USB connection for your imaging camera or other accessories. GPS is optional rather than built in, so location and time information can be entered through the controller when setting up.
The mount operates on 12V DC power and draws approximately 0.5 amp while tracking and 0.8 amp during GoTo slews, according to iOptron's specifications. That relatively modest electrical demand is useful when operating from a portable field battery, although your total power requirements will depend on any cameras, dew heaters, and other equipment used alongside the mount.
What Owners Say on Cloudy Nights
One interesting thing about discussions of the CEM26 on Cloudy Nights is how differently observers approach the same equipment. Some want an electronic polar scope, automatic guiding, and complete computer control. Others would rather keep things simple, and AccuAlign remains attractive to that second group.
In one discussion about choosing a CEM26, an observer looking to replace a smaller equatorial mount specifically wanted the AccuAlign version for use with a 90mm refractor. His reasoning was straightforward: he was already comfortable with optical polar alignment, wanted enough capacity for a somewhat larger telescope, and preferred not to bring guiding equipment, software, and a laptop into his observing routine.
Another CEM26 owner reported being particularly pleased with the AccuAlign polar scope after using it with an 80mm refractor for astrophotography. His experience illustrates that a traditional polar finder can still be a useful part of a modern imaging system, even if computer-assisted methods offer additional convenience.
Experienced owners also make a useful distinction between visual observing and long-exposure photography. An optical polar alignment that is entirely satisfactory for keeping Saturn centered in the eyepiece may still need refinement or autoguiding when you're collecting several-minute exposures at a demanding image scale. Neither approach is inherently better; the equipment should match the kind of observing you enjoy.
Under the Night Sky
Put a compact 4" refractor on the CEM26 and you have an observing system capable of showing a remarkable variety of celestial objects without requiring a large vehicle or a second person to help set it up.
On a clear spring evening, start with the galaxies in Leo. The Leo Triplet places M65, M66, and NGC 3628 within reach of a low-power, wide-field eyepiece under sufficiently dark skies. Move north to the Whirlpool Galaxy, M51, where a small telescope will show the brighter central regions and its neighboring companion galaxy, with additional structure becoming apparent as aperture, transparency, and sky darkness improve.
Summer offers an entirely different kind of observing. The rich star fields of the Milky Way contain the Lagoon and Trifid Nebulae, the Swan Nebula, and the innumerable star clusters scattered through Sagittarius and Scutum. The Double Double, Epsilon Lyrae, gives you an opportunity to test the resolution of your telescope and the steadiness of the atmosphere. At higher magnifications, good tracking becomes especially welcome as you work to separate its close stellar pairs.
When autumn arrives, the Andromeda Galaxy, the Double Cluster, and the bright planetary nebulae of the northern sky provide an enjoyable progression from wide fields to higher-power observing. In winter, Orion takes center stage, with the Trapezium stars embedded in the glowing heart of M42.
None of these objects requires a laptop to enjoy. Select your target on the Go2Nova hand controller, let the mount find it, and spend your time looking through the eyepiece. The CEM26 continues to follow the object while you change eyepieces, examine details, or share the view with someone else.
Observing Tip: Get Comfortable with AccuAlign Before Dark
If this is your first equatorial mount, spend a little time during daylight becoming familiar with the altitude and azimuth adjustment controls, the counterweight arrangement, and the illuminated polar scope. Learn how to display the pole star position on the Go2Nova hand controller, and make sure you've entered the correct location, time zone, date, and time.
When evening comes, set the tripod on reasonably level ground, position the mount approximately toward north, and balance the telescope with the gear locks disengaged according to the manual. Re-engage the locks before powering the mount and beginning its normal operation.
After dark, use the controller's pole star display to position Polaris correctly on the AccuAlign reticle. The reticle illumination helps you see its markings against the dark sky without losing sight of the star. Once the mechanical adjustments are complete, perform the appropriate GoTo star alignment to improve pointing accuracy.
For visual observing, a careful optical alignment will often be all you need. If you're planning a night of long-exposure imaging, take the additional time to check your alignment with iOptron's available alignment routines or a drift alignment procedure. A few extra minutes spent setting up can save considerable frustration later in the evening.
Frequently Asked Questions
- Should I choose AccuAlign or iPolar?
- AccuAlign is an optical polar finder that allows you to align the mount without a computer. iPolar uses a built-in camera and computer software. For observers who prefer traditional equipment or primarily observe visually, AccuAlign is a practical choice. For imagers who routinely bring a laptop into the field, iPolar may be more convenient.
- Can I use the CEM26 for astrophotography?
- Yes. The CEM26 supports guided astrophotography through its ST-4 port or compatible USB/ASCOM control. Compact refractors and camera-based imaging systems are particularly suitable. Plan to use autoguiding for demanding long-exposure imaging.
- Can I polar align if Polaris is blocked?
- Yes. The Go2Nova controller includes a Polar Iterate Align routine using two bright stars elsewhere in the sky. The mount still needs a reasonable initial setup, and precise imaging may require additional refinement.
- Does this package include a hard case?
- No. The C261B3 includes the AccuAlign polar scope and 1.75" LiteRoc tripod, but not a hard carrying case. A compatible iOptron hard case is available separately.
Supplied Accessories
- iOptron CEM26 center-balanced equatorial mount head
- Built-in AccuAlign optical polar scope with LED illuminator and cable
- Go2Nova 8409 computerized hand controller
- 3.8" adjustable Vixen-style dovetail saddle
- 1.75" LiteRoc stainless steel tripod
- Die-cast tripod spreader and accessory tray
- 10 lb (4.5 kg) counterweight
- Stainless steel counterweight shaft with extension
- Hand controller and declination connection cables
- USB connection cable
- 100–240V AC adapter for indoor use
- Quick Start Guide
Optional Accessories
iOptron CEM26 Hard Case: Provides a fitted protective case for transporting and storing the mount head.
iOptron External GPS Receiver: Automatically supplies time and location information for the hand controller.
Guide Scope and Guide Camera: Useful additions for long-exposure astrophotography when you want to correct small tracking errors during an exposure.
Additional Counterweights: Available for telescope combinations requiring a different balance arrangement.
Final Thoughts
There are larger equatorial mounts that can carry more weight, and there are smaller tracking mounts that can be packed into a camera bag. The CEM26 occupies a useful place between those two extremes. Its 10-pound head is easy to live with, the 26-pound payload rating gives it room for a capable visual or imaging system, and the LiteRoc tripod adds stability without turning the entire package into something you're reluctant to carry outside.
I particularly like the reasoning behind the AccuAlign version. Electronic polar alignment is a useful development, especially for astrophotographers, but it doesn't make the optical polar scope obsolete. For someone who understands how to align a telescope on Polaris, or simply enjoys the process, AccuAlign does the job without requiring another computer, cable, or software program.
And if your interests change, the CEM26 already has the electronic controls, autoguiding connections, and mechanical capabilities to accommodate a more involved imaging system. You aren't buying a mount that must remain permanently tied to one style of observing.
Sometimes the best telescope equipment is the equipment you're willing to carry outside on a Tuesday evening when the sky unexpectedly clears. The CEM26 with AccuAlign and LiteRoc has a great deal going for it in that respect.
