iOptron CEM25P Review
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iOptron CEM25P Review

Small, Quite and Light

Last year I had to curtail my Astronomy activities due to limited available free time, but this year I am picking up where I left off, with some new gear. This will be a new project for me and it should be fun to put together. A simple lightweight solar tracking and imaging solution that doubles as my grab and go for night time viewing. 

Doing some basic research and for my criteria of light, portable, quiet with a payload of at least 25lbs, I choose the iOptron CEM25P. iOptron offers these mounts in a couple of configurations depending on how precise you need the tracking to be or with a larger 2" tripod. The cost is reasonable running around $1,000.00 for a CEM25P version.

Assembly: The mount and tripod arrive in two boxes and went together in just a few minutes, no surprises. Everything was straightforward. 

Build Quality: Overall, very good and of a solid build with a fit and finish that is appealing to the eye. Nothing appeared to be or felt of cheap quality. I was impressed with the build showing very tight & minimal movement after all the parts are tightened down. I had one small area on the RA which showed a paint touch up during quality control, nicely done.

The Tripod: A Steel Tubular with 1.5" or 2" legs depending on which version you purchase. The tripod is solid with the lower section sliding down to raise and lower the tripod, and has standard hardware that the end-user can adjust to ensure it stays nice and tight. The tripod folded down is about 28 inches and when fully extended stands about 43" at the mounting plate for the head. iOptron offers a "tall" version, and I would have gone with that one but was not in stock. So, I ordered an 8-inch extension to facilitate the telescope being pointed high in the sky. Like other smaller tripods, it has a center spreader that doubles as a tray and holder of eyepieces and is an integral part of the tripod's stability as you tighten down the spreader it forces the legs out under tension.  If you are in the market for an iOptron CEM25 I would recommend opting for the larger 2" tripod version.  Observation:  The tripod legs have a tendency rust, keep an eye on moister or storage in humid environments.

The Head: The bread and butter of the system has the following inputs: 

  • 12v DC input either from the included A/C power adapter or as I have chosen use an external 12VDC source (more on this later). 
  • Inputs for the GotoNova Hand Controller, 
  • Power Input for Polar Scope recital
  • The serial port at the Hand Controller Base allows you to use your PC to control the mount using wires as well as update the Firmware. See the wireless option below. 
  • A standard Guide Port is available for your guide cameras. The head uses a Spring-loaded vixen style dovetail mounting system.
  • Balancing Act: The mount ships with one 10lb counterweight and according to iOptron will balance a load of 13 lbs, so you may need more weight if your OTA exceeds that.  iOptron uses a friction-free system, and you are cautioned that 1. you must dis-engage both RA and DEC worms and 2. Hold on to your OTA when you do to prevent it from freely rotating around and banging into the mount. Me personally I prefer the clutch systems, but anyway, once you disengage the worms using the two small thumb screws, and turn the locks to unlock - just follow the balance routine as outlined in the manual. Once everything is a balanced return to zero position and lock the RA and DEC, then tighten the worms fully down then back off as specified in the manual to prevent stress or binding, it should be tight enough to engage and fill snug but not fully screwed down.

Operation of the Head: The head incorporates Stepper Motors, which is a blessing; If for some reason your telescope strikes your mount or is bumped hard, no damage will occur to the motors or electronics.

The head operates silky smooth and extremely quiet, you have control over the slew, tracking rates at the touch of a button or set in the hand controller. The head moves and tracks flawlessly. For such a small size this little CEM 25P works very well, and I am impressed with the options. During indoor testing, I was able to slew, and tracking objects in record time, without having to read volumes of information. Using the hand controller you have the ability to manually slew the mount as you desire.

Alignment: Your alignment process depends on your location, visibility of Polaris, or other bright stars. The software allows for at least 3 ways to align the mount. Alignment methods include Polar, Traditional Polar, BrightStar Polar,  If I have not mentioned the mount does have a small level at the top of the head but I would have a larger one since the built-in one is very small, having the mount level is important to the tracking process.

Software & Database: The CEM25P uses iOptron's GOTONOVA® GOTO technology, offering the end-user a powerful and accurate GOTO mount. The available database includes over 150,000+ objects and the Hand Controller is easy to navigate and is intuitive enough to start using without having to refer to a manual as long as you understand very basic Astronomy terms. The Hand Controller uses a 4-line LCD screen that makes it a simple process for setting up the telescope and locating your favorite objects in the night sky. 

The iOptron offers a Wireless interface as an option called StarFi, which allows the use of smart devices and PCs to control the mounts to go to functions as well as upgrading the firmware. 
Some of the technology used in the CEM25 originates from the big brother CEM60.
GPS: Built-In, although I could not get a lock indoors next to a large window. But even so, you still have the ability to manually set the parameters, when the GPS is locked all that is done automatically for you.

Power: If you set up your iOptron CEM25P close to A/C outlets you can use the supplied power supply but if you find yourself away from AC power, the mount will accept standard 12 volt DC in.  I purchased a HALF Minute Power 12v Portable Car Battery Jump Starter that works fine with the mount and is very portable.  The battery pack has a convenient battery level readout, with a charger and other accessories.  The portable battery also supplies USB out power for your smartphone if needed + a small flashlight, and don't forget can jump-start your auto if need be.

My Overall Opinion and recommendations are that this iOptron CEM25P is well suited as an upgrade to most entry-level mounts that are packaged with smaller telescopes. The CEM25P is suitable for intermediate level GOTO operations and supports guided imaging for routine Astrophotography needs. There is nothing much not to like about the mount, the design and quality is very good and should satisfy anyone looking for a light, quite mount. To maximize this mount you will get optimal results using shorter telescopes to reduce any movement caused by the wind.

The one frustration I had was reading the owners manual and finding a lack of information on most of the topics it covered technically. I felt after reading through the manual I have sill guessing about certain aspects of the operations, such as enabling "guiding", the manual just mentions it has a guide port compatible with ST-4, no details further than that. iOptron should spend more time developing their owner's manuals.

Yes, I would recommend this iOptron CEM25P to anyone who needs a small, quiet, portable GOTO mount.

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Collapse Expand Comments (2)
Noel Tabor


I am interested in buying this for Astrophoto. I want to use my 100-400mm lens(effective focal length 800). my camera WITH lens is under 4lbs. Will this mount be useable without the counter weight? I have a slim dream of packing this into a packpacking trip. my other option is a Ioptron Smart EQ


For your situation I would go with a iOptron Star Guider. The CEM 25 would be a heavy back packing option for what I believe you need.

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