The darkest skies are rarely in your backyard. They may be two hours away at a favorite observing site, across the state at a star party, or at the end of a gravel road where the nearest streetlight is miles behind you. Getting your equipment there safely, setting it up without too much fuss, and bringing everything home again are all part of the experience. The iOptron CEM26 C262A3 is a particularly sensible equatorial mount package for observers and astrophotographers who regularly travel to find better skies.
It combines iOptron's remarkably portable 10-pound (4.5 kg) center-balanced equatorial mount with a 26-pound (12 kg) payload capacity, the built-in iPolar electronic polar scope, a sturdy 1.75" LiteRoc stainless steel tripod, and a fitted aluminum hard carrying case for the mount head. The tripod, counterweight, and telescope travel separately, leaving you with manageable pieces rather than one awkward assembly to carry from the car to the observing field.
The C262A3 is essentially the C261A3 package with the addition of iOptron's protective case. That may seem like a modest difference, but anyone who has transported an equatorial mount more than a few times will appreciate having a secure place for its precision mechanical components. You can buy the case separately, of course, but this package includes it from the beginning.
Taking a Precision Mount on the Road
An equatorial mount isn't particularly fond of being knocked around in the trunk of a car. Its worm gears, bearings, polar alignment adjustments, and other precision components are designed to move accurately and smoothly, not to absorb the bumps and jolts of an unprotected trip down the highway.
The supplied aluminum hard case provides a dedicated place to store and transport the CEM26 mount head, protecting its protruding controls and mechanical components from ordinary handling damage. It also makes keeping the mount organized considerably easier. Instead of finding somewhere to wedge a bare mount head between the telescope case, counterweights, and assorted equipment bags, you have a protective case intended for the instrument.
The case is for the mount head rather than the entire assembled equatorial mount. The LiteRoc tripod and 10-pound counterweight travel separately. That's actually a useful arrangement when loading a vehicle, since you can distribute the weight and pack the individual components where they fit best.
The CEM26's light weight is another advantage when traveling. The head weighs only 10 pounds, despite a manufacturer-rated payload of 26 pounds excluding the counterweight. iOptron's center-balanced design positions the weight of the telescope and mount more directly over the center of the tripod, improving the mechanical balance of the system without requiring a large, heavy mount head.
A 26-pound payload rating doesn't mean that every telescope weighing 26 pounds is equally suitable. A long optical tube places different demands on a mount than a compact telescope of the same weight, particularly in the wind. iOptron recommends optical tubes smaller than 6" in diameter, and the length, balance, and imaging focal length of your telescope should also figure into the decision. Compact apochromatic refractors, small astrographs, and camera-based imaging systems are especially attractive combinations for a portable CEM26.
Getting Polar Aligned at an Unfamiliar Site
One inconvenience of traveling with an equatorial mount is that you must establish polar alignment every time you set up in a new location. Your mount's right ascension axis needs to be pointed toward the celestial pole so its tracking motor can compensate for the Earth's rotation. The more accurately you do this, the less unwanted motion you will have to correct during an astronomical exposure.
The C262A3 includes iOptron's iPolar electronic polar scope, built into the mount's right ascension axis. Unlike a conventional optical polar finder, which requires you to look through a small telescope and position Polaris on a reticle, iPolar uses a camera to identify the star field around the celestial pole.
Connect iPolar to a compatible computer running iOptron's software, and the system determines where the mount is pointing in relation to the pole. The software then shows you how to adjust the mount's altitude and azimuth controls. As you make those adjustments, the display helps you bring the mount into alignment.
One particularly useful characteristic is that Polaris itself does not have to be visible. The iPolar camera can identify the surrounding star field and determine the pole's position without using Polaris as its reference star. It still needs enough visible sky near the pole to recognize the field, however. A completely obstructed northern horizon cannot be overcome simply by using an electronic polar scope.
This can make a considerable difference at unfamiliar observing sites. A tree that didn't appear especially troublesome when you parked the car may turn out to be directly in front of Polaris, or the only reasonably level place to set up may have a partial obstruction to the north. iPolar gives you some flexibility in those situations, and it also eliminates the need to kneel behind the mount and look through a small optical finder while adjusting its position.
For astrophotographers already using a computer to control their cameras, iPolar fits naturally into the setup procedure. It does require a computer for its own alignment software, but the mount's normal GoTo and tracking functions can still be operated from the supplied Go2Nova hand controller without leaving the computer connected to iPolar.
A Portable Mount with Substantial Mechanics
The CEM26 is much more than a camera tracker with a large payload rating. Its right ascension and declination axes use 3.46" (88mm) aluminum worm wheels with 144 teeth, driven by 0.60" (15.2mm) brass worms through synchronous belts. The 1.38" (35mm) steel axis shafts are supported by 2.17" (55mm) ball bearings.
The worm gears provide the small, controlled movements necessary to follow celestial objects as the Earth rotates. The belt transmissions transfer power from the motors to the worms without the additional gear-to-gear reduction stages found in some mount designs. The substantial shafts and bearings support the telescope as the mount moves across the sky, while the center-balanced design helps keep the load positioned over the tripod.
iOptron specifies periodic error of less than ±12 arcseconds over the mount's 600-second worm period, measured under the manufacturer's bench test conditions. Periodic error is the small, repeating variation in tracking that results from imperfections in a worm-drive system. The CEM26's Permanent Periodic Error Correction (PPEC) can record corrections for the repeatable portion of this error and retain that information for subsequent sessions.
For longer photographic exposures, the mount also supports autoguiding through an ST-4-compatible port or appropriate computer control using USB and ASCOM. An autoguider watches a reference star and tells the mount when small tracking corrections are needed, allowing you to collect exposures that would be more difficult with the mount operating on its own.
This is the standard CEM26 rather than the more expensive CEM26EC with a high-precision right ascension encoder. For demanding long-exposure imaging, I would plan on using an autoguider, even with careful polar alignment.
The mount includes large quick-lock gear engagement controls for balancing the telescope, an adjustable counterweight shaft, and a 3.8" Vixen-style dovetail saddle. The saddle accepts standard Vixen-format plates, but not the wider Losmandy D-style dovetails used on some larger telescopes.
The LiteRoc Tripod
A good mount needs a good foundation. That is especially important at a dark sky site, where the ground may be uneven, the wind may pick up after sunset, and there isn't always a convenient place to reposition the equipment once everything has been connected and aligned.
The C262A3 includes iOptron's 1.75" LiteRoc stainless steel tripod, which weighs approximately 16.5 pounds (7.5 kg). It is more substantial than the lighter 1.5" tripod supplied with some other CEM26 packages. Its larger legs and metal spreader provide a firmer platform, helping resist vibration from focusing, handling, and light breezes.
The tradeoff is a little additional weight to carry, but I think the combination is well chosen. The CEM26 head remains light and easy to handle, while the heavier support is positioned where it can do the most good. When you're trying to photograph a faint galaxy or nebula over several hours, a stable foundation is more valuable than saving a few pounds in the tripod.
GoTo Control and Power in the Field
The supplied Go2Nova 8409 hand controller contains a database of approximately 212,000 astronomical objects, including familiar Messier, NGC, IC, and Caldwell objects, along with thousands of stars and other celestial targets. Once the mount has been properly aligned, you can select an object and let the CEM26 slew to it automatically.
Built-in Wi-Fi provides another way to operate the mount through compatible software, and a USB connection allows computer control through ASCOM. The Wi-Fi controls the mount itself; it does not function as a wireless USB connection for cameras, focusers, or other imaging accessories.
The CEM26 runs from a 12V DC supply and draws approximately 0.5 amp while tracking and 0.8 amp during GoTo slews, according to iOptron's specifications. That is a modest electrical requirement for a computerized equatorial mount and makes battery operation practical at remote sites. Your imaging camera, dew heaters, computer, and other accessories may consume considerably more electricity than the mount, so calculate your complete system's power requirements before heading into the field.
GPS is optional rather than built in. You can enter the observing site's location and time through the hand controller, supply appropriate information through compatible computer software, or add iOptron's external GPS receiver to simplify setup when traveling between locations.
What Owners Say on Cloudy Nights
One of the more useful CEM26 discussions on Cloudy Nights came from an owner who purchased the iPolar version with the 1.75" LiteRoc tripod from Astronomics. His equipment included an Astro-Tech AT72EDII refractor, a ZWO ASIAIR Pro, a guide scope and camera, an electronic focuser, and a cooled imaging camera. He reported that the supplied counterweight was sufficient to balance the equipment, and that the combination felt secure when assembled.
He was particularly pleased with iPolar, reporting that the polar alignment procedure was straightforward after setting up the mount. Just as importantly for a traveling observer, he found the hard case very useful for organizing the equipment and described the system as practical to pack into a car for an observing trip.
Other Cloudy Nights owners have made similar observations about the CEM26's portability, particularly when paired with smaller imaging refractors. There are also discussions about the tradeoffs involved in choosing the heavier LiteRoc tripod and about the additional demands that larger optical tubes place on a mount this size.
Those experiences are worth considering because they reflect the way people actually use their equipment. A payload rating tells you how much a mount is designed to carry. An observer who repeatedly loads the equipment into a vehicle, sets it up at a dark site, and collects images throughout the night can tell you something equally useful about how pleasant the system is to own.
Under the Night Sky
A genuinely dark sky can change what a small telescope or camera lens is capable of recording. Objects that are difficult to separate from the background glow of suburban skies begin to reveal faint outer structures, delicate nebulosity, and dust clouds that would otherwise be lost in light pollution.
During the summer, a short imaging refractor on the CEM26 opens up an extraordinary collection of targets along the Milky Way. The Lagoon and Trifid Nebulae make a beautiful wide-field combination when the telescope and camera provide a sufficiently large field. The Eagle Nebula, Swan Nebula, and the extensive emission regions of Sagittarius offer projects that can occupy many clear evenings.
For an even wider field, put a camera lens on the mount and photograph the Rho Ophiuchi cloud complex near Antares. The colorful combination of reflection nebulosity, reddish emission regions, and dark interstellar dust is one of the most remarkable photographic subjects in the summer sky, particularly from a location with a clear southern horizon.
As autumn approaches, the Veil Nebula in Cygnus becomes a rewarding project for a small apochromatic refractor. The delicate filaments of the supernova remnant extend across a substantial region of sky, while the North America and Pelican Nebulae provide enormous fields of glowing hydrogen and intervening dark dust. Later in the year, the California Nebula, the Heart and Soul Nebulae, and the Rosette provide additional opportunities to take advantage of a wide-field imaging system.
The attraction of a portable mount isn't simply that you can photograph these objects. It's that you can take your equipment somewhere the sky gives you a better opportunity to record them. A capable imaging telescope in a dark location can sometimes provide a more satisfying result than considerably more expensive equipment struggling against the glow of city lights.
Observing Tip: Prepare Your Equipment Before the Trip
One of the easiest ways to shorten setup time at a dark sky site is to balance your equipment at home before you travel. Assemble the telescope, camera, guide scope, and other accessories exactly as you intend to use them, then carefully balance the right ascension and declination axes.
Once you've found the proper positions, put a small piece of removable tape on the counterweight shaft to mark the weight's location and another on the telescope's dovetail bar to indicate its position in the saddle. When you arrive at your observing site, those marks give you a convenient starting point for balancing the equipment again. Always check the balance before engaging the drive gears, particularly if you've changed an eyepiece, camera, or other accessory.
If you use several different telescope configurations, different colored tape marks can help distinguish them. A little preparation at home can save you from spending the first half hour of a clear evening rearranging counterweights in the dark.
It's also worth testing your complete electrical setup before leaving home. Connect the mount, iPolar, guide camera, imaging camera, and computer to the same power equipment and cables you plan to bring into the field. Discovering that a USB cable is too short or that a power connector doesn't fit is much less frustrating in the backyard than at an observing site two hours from the nearest store.
FAQ
- What is the difference between the C262A3 and C261A3?
- Both packages include the CEM26 with iPolar, the 1.75" LiteRoc tripod, and a counterweight. The C262A3 also includes iOptron's aluminum hard carrying case for the mount head.
- Does iPolar require a laptop?
- Yes. iPolar uses a computer running iOptron's polar alignment software and connects through its own USB interface. The mount's GoTo and tracking functions can still operate independently through the Go2Nova hand controller.
- Does the hard case hold the entire mount?
- No. The included case is intended for the CEM26 mount head. The LiteRoc tripod, counterweight, telescope, and other equipment must be transported separately.
- Does iPolar need a clear view of Polaris?
- No. iPolar can determine the celestial pole from surrounding stars without requiring Polaris itself to be visible. It still requires a sufficiently unobstructed view of the polar region to identify the star field.
- Can the CEM26 be used for astrophotography without autoguiding?
- Short unguided exposures are possible, depending on focal length, image scale, polar alignment, and tracking conditions. For demanding long-exposure deep-sky imaging, an autoguider is recommended.
Supplied Accessories
- iOptron CEM26 center-balanced equatorial mount head
- Built-in iPolar electronic polar scope
- Aluminum hard carrying case for the mount head
- Go2Nova 8409 computerized hand controller
- 3.8" adjustable Vixen-style dovetail saddle
- 1.75" LiteRoc stainless steel tripod
- Die-cast metal tripod spreader and accessory tray
- 10 lb (4.5 kg) counterweight
- Stainless steel counterweight shaft with extension
- Mount connection cables
- 100–240V AC adapter for indoor use
Optional Accessories
iOptron External GPS Receiver: Automatically supplies observing location and time information, which can be useful when traveling between different observing sites.
Guide Scope and Guide Camera: Recommended for long-exposure deep-sky imaging, allowing the mount to correct small tracking errors during an exposure.
12V Field Battery: Provides electrical power for the mount when an AC outlet isn't available. Choose sufficient capacity for your complete observing or imaging system.
Dew Control System: Helps prevent moisture from accumulating on telescope and guide scope optics during long sessions, especially in humid conditions.
Final Thoughts
There is something satisfying about arriving at a dark sky site with equipment that was chosen for the trip rather than simply brought along because it was already in the garage. The CEM26 is light enough to carry comfortably, the LiteRoc tripod gives it a substantial foundation, and iPolar makes accurate polar alignment more convenient when you're setting up somewhere unfamiliar.
The C262A3 takes that combination a step further by including a proper case for the mount head. It's a small addition in the overall scheme of things, but one you'll appreciate every time you load the car or put your equipment away after a long night.
I think this package makes particular sense for someone using a small apochromatic refractor or compact imaging telescope who regularly travels to darker skies. It offers the capabilities of a computerized equatorial mount without demanding the weight and bulk of a much larger system, and the included case removes one more detail from the list of things you have to purchase separately.
Most of us don't get nearly enough perfectly clear, moonless nights. When one finally comes along, it's nice to have a mount that's ready to go wherever the sky looks best.
