iOptron Enters the Strain Wave Mount Market: Review of the iOptron HEM44EC


iOptron recently introduced the HEM, HAE, and HAZ lines of mounts featuring strain wave drives in equatorial, azimuth-equatorial, and altitude-azimuth configurations, respectively. I was fortunate to be the first in the United States to acquire the iOptron HEM44EC, one of the newest mounts on the market.


As with others in iOptron’s equatorial HEM family of mounts, the HEM44EC employs a strain wave motor for the RA axis but a worm gear/belt drive on the Dec axis. This shouldn’t be an issue for astrophotography given an accurate polar alignment, with Dec less likely to need adjustment than RA.

iOptron offers two sizes of all its HEM-class mounts, with payload capacities of 14kg (30lbs) and 20 kg (44lbs) and incredibly low weights of about 3.5kg (8lbs) and 5.9kg (13lbs), respectively. The HEM44EC is the larger option. Strain wave mounts do not require counterweights but the resulting torque on the motors does limit payload capacity. iOptron’s HEM and HAE lines offer an optional 4.5kg (10lbs) counterweight and shaft that increases the capacity by about 5kg (11lbs). iOptron rates payload capacities assuming a lever arm of 200mm.

Latitude adjustment with the HEM equatorial mounts is limited to between 15 and 65 degrees north/south, a narrower range than many other strain wave mounts. iOptron’s HAE AZ/EQ mounts boast a 0-to-90-degree range.

The HEM44 base model costs $2,698, with an iPolar scope as a $100 option. I opted for the EC variant, which includes the polar scope and high accuracy encoders, a $1300 option.

All HEM-class mounts use the new Go2Nova 8409 hand controller with USB 2.0 and Wi-Fi ports for PC control through a redesigned iOptron Commander interface (not yet incorporated into common control software at the time of writing). The Go2Nova 8409 is also compatible with the iOptron Commander Lite app. Notably absent is a GPS synch module, but time and location can be imported to the mount from a PC or phone through the iOptron Commander Lite app.


The author’s HEM44EC on an iOptron Carbon Fiber Tripod and 6” Minipier carrying a Takahashi FSQ85EDX with a ZWO ASI2600MC Pro camera. Piggybacked is a William Optics Zenithstar 71mm guide scope with a QHY 5L-II M guide camera and spotting scope. Credit: Daniel Moomey


I tested the performance of the HEM44EC for imaging on a dozen occasions with a total of 78 hours of guiding using PHD2 software. The guiding accuracy of the HEM44EC maintained a weighted average RMS of 0.77 arcsec with the payload shown in the image above. This is  approximately two times better than what I experienced using the iOptron GEM45 (reviewed for AGT here), which performs well in its own right for its price point. I expect much of this performance improvement is because of the high accuracy encoders. The lowest 4-minute average RMS guiding error I achieved with the HEM44EC was 0.34 arcseconds, as shown in the screen shot below. 


Exceptional PHD2 guiding, within 0.34” RMS. Credit: Daniel Moomey

To determine if guiding performance varies as the payload changes, which can change the torque on the RA motor, I reconfigured the payload to allow weights to be attached on the telescope as shown below.


Testing tracking with additional weights attached to the telescope. Credit: Daniel Moomey

Tracking performance was evaluated with my photographic setup with and without weights added, while a third configuration pushed the mount to its maximum rated weight capacity and increased the moment arm to 290mm, exceeding the recommended torque rating for the mount.

As expected, higher elevations and higher payload mass yielded poorer tracking performance, primarily due to the higher torque on the motors from the payload being cantilevered when pointing near zenith.

The average RMS tracking performance remained below one arcsecond even when testing at the maximum rated payload weight. As such, I have no concerns about operating this mount up to the maximum torque rating of 39Nm. This is equivalent to a Celestron 9.25” Edge HD with camera and off-axis guider (about 14kg), or a larger refractor in the range of 100-120mm in aperture. At this price point, the mount’s performance is quite impressive even when carrying larger loads. Because lighter payloads did not yield much improvement in tracking performance, users with payloads below 12kg may want to opt for one of the lower payload strain wave drive mounts coming onto the market. Note that both the weight and torque of the moment arm on the strain wave gear need to be considered in determining what it can carry.

Features, Fit, and Finish

iOptron made a few changes to the mount design compared to the GEM45 I’m used to. A big one for me was the removal of the internal USB 2.0 hub, opting instead for a single USB 2.0 passthrough. The iPolar scope, PC control, and USB accessories thus all require separate USB connections.  iOptron told me the hub in other models was experiencing a high failure rate, which affected function of the iPolar scope. The iPolar port is located on the back of the RA housing and uses mini-USB for the iPolar connection to avoid confusion with the USB-B passthrough. I would have preferred a USB-B or C type connection for better stability and long-term reliability. I also asked iOptron why they haven’t implemented USB 3.0 across their entire lineup. Apparently, I’m not the only one who has made that suggestion. I wouldn’t be surprised to see that implemented in future lineups.


Back Panel housing of HEM44EC with 12V DC out port on top and bottom of Go2Nova 8409. Credit: Daniel Moomey

The back panel ports felt loose so I disassembled the back panel and found the PCB boards aren’t firmly secured. The slight movement of the ports feels uncomfortable but it doesn’t look like long-term reliability will be affected.


The internal PCBs shown to sit loosely in channels (circled in red) which are machined out of the aluminum RA housing. Credit: Daniel Moomey


Video showing the movement of the ports. Credit: Daniel Moomey


The HEM series mounts have a Vixen and Losmandy dovetail mount, though iOptron did not implement a traditional dual saddle. Users must convert the saddle between the two dovetail standards. There is a clear step-by-step guide for converting the saddle in the HEM manual, which is available on the iOptron website here. Performing this conversion requires removing the saddle plate from the Dec axis. Twelve bolts need to be removed, four of which have coaxial springs that can easily be dropped and lost. iOptron told me this design choice was made in favor of reducing weight. I would have preferred the minor weight penalty for the simplicity and efficiency of a true dual saddle.

I don’t like that the mount is limited to between 15 and 65 degrees latitude adjustment by the CEM40/GEM45 yoke used to connect the mount to the tripod. The yoke could easily have been redesigned for full latitude range. And it seems that is now the case with the HAE (azimuth-equatorial) product line.


I have both the iOptron Literoc Tripod (LRT) and the new Carbon Fiber Tripod (CFT), and both are quite stable and capable of handling this mount. The LRT weighs 10 lbs. more than the CFT, so for a lightweight travel setup the CFT may be worth considering. It’s also $60 cheaper than the LRT. Note, though, that the CFT’s lower height means it has a significantly smaller footprint than the LRT when set up with the legs collapsed. Without a counterweight, slewing the telescope to high elevations can drastically shift the center of gravity of the system. I hang about 30 lbs. of weight from the CFT to lower the center of mass, which helps keep the telescope stable for high winds and when pointing at high elevations. This is, of course, less of an issue with the legs extended. iOptron also offers the MiniPier 8031 to raise the height of HEM series mounts on these tripods, a useful add-on for those with long imaging trains.


6” MiniPier 8031 between the CFT tripod and the HEM44EC mount. Credit: Daniel Moomey

Using the optional 4.5 kg counterweight and shaft, I believe, comes down to personal preference and budget. If portability is less of a concern, the same 20kg payload capacity the HEM44 is rated for without the counterweight (based on a 200mm moment arm) can be achieved with the smaller HEM27 mount with the counterweight and at a much lower price point. I have not evaluated tracking and imaging performance when using a counterweight.

A hard carrying case is included. The case fits nicely into an airplane check bag but I would recommend putting it in a more bulletproof container like a Pelican case for flying.

Final Thoughts

Overall, I am extremely happy with the quality, features, and performance of my HEM44EC. It has a lot to offer in terms of performance at its price point. If you need high or low latitude adjustment, or prefer a strain wave Dec motor, then the HAE line of mounts or those from other manufacturers may also be worth looking at.


Heart Nebula, 425x 300sec, Takahashi FSQ85 quadruplet and ZWO2600MC PRO, using Optolong LX-Extreme filter from Bortle 7 skies, mounted on the iOptron HEM44EC. Credit: Daniel Moomey


Veil Nebula, 200x 300sec, Takahashi FSQ85 quadruplet and ZWO2600MC PRO using an Optolong LX-Extreme filter from Bortle 7 skies, mounted on the iOptron HEM44EC. Credit: Daniel Moomey

HEM44EC Introductory price: $4,148

Carbon Fiber Tripod: $318

6” MiniPier 8031: $118

Counterweight and Bar: $120



About Daniel Moomey

I've spent 16 years with Dept. of Defense space operations, testing, and research. I'm currently a PhD candidate in space systems engineering, and the Technical Director for a government laboratory. I love engaging with STEM outreach and education opportunities. I've also been informed I'm a "gear nut" and that I suffer from severe GAS (Gear Acquisition Syndrome). What can I say, some people like Pokémon, I like collecting photons and photon collectors.

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