The iOptron HEM44EC takes the portability and 44-pound counterweight-free capacity of the HEM44 and adds a high-precision encoder to the right-ascension axis.
The mount head weighs just 13.65 lb (6.2 kg) with the saddle installed, yet iOptron rates it to carry 44 lb (20 kg) without a counterweight. Add the optional counterweight system and the published capacity rises to 55 lb (25 kg).
The HEM44EC's high-precision RA encoder works with iOptron's Real-Time Periodic Error Correction to continuously reduce the tracking error produced by the strain-wave drive. That can make unguided imaging practical with some short-focal-length systems, but its value does not disappear when you guide. The encoder can also allow much longer guide exposures while it handles the faster RA tracking error internally.
This H444 version does not include iPolar, making it a particularly good fit for imagers who already polar align through NINA, SharpCap, ASIAIR, PHD2, or another camera-based routine.
Features
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High-precision RA encoder with Real-Time PEC. The encoder continuously monitors right-ascension motion and allows the mount to correct much of the strain-wave drive's tracking error internally.
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44 lb counterweight-free payload. Carry up to 20 kg (44 lb) without a conventional counterweight shaft and stack of weights.
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Only 13.65 lb with the saddle installed. A payload-to-mount-weight ratio of approximately 3.2:1.
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Up to 55 lb with a counterweight. Add the optional shaft and 10 lb counterweight when a heavier or more demanding telescope configuration calls for additional capacity.
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Hybrid drive system. Right ascension uses a 640:1 strain-wave drive while declination uses iOptron's backlash-free worm-and-belt system.
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270-second RA gear period. The high-precision encoder and Real-Time PEC work directly with the tracking behavior of the strain-wave RA drive.
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Long-cadence guiding. iOptron specifically notes that the EC version can often use guide exposures in the 5–10 second range rather than the very short corrections commonly used with non-encoder strain-wave mounts.
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Particularly useful with an OAG. Longer guide exposures give an off-axis guider more time to collect signal from faint stars while the encoder continues controlling the RA axis.
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RA guiding control. The hand controller allows external RA guide corrections to be accepted or filtered while the encoder continues handling the RA tracking system.
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Go2Nova 8409 hand controller included. Standalone GoTo operation with an approximately 212,000-object database.
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Wi-Fi through the hand controller. The 8409 provides wireless connectivity for compatible applications such as iOptron Commander Lite and SkySafari.
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Integrated ST-4 autoguider port. Traditional autoguiding remains available in addition to software-based pulse guiding.
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Through-mount cable management. Two 12V accessory connections and USB 2.0 pass-through help keep camera and accessory wiring away from the moving axes.
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Electronic friction brake. Designed to stop the mount safely during a planned or unexpected interruption in power.
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Power-down position memory. The mount retains its position through a power interruption so operation can resume without starting the positioning process from the beginning.
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Automatic zero-position search. Built-in sensing allows the mount to locate its reference position electronically.
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Vixen/Losmandy-D convertible saddle. Accepts either common dovetail standard.
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Dedicated equatorial operation. The HEM44EC is designed specifically as an EQ imaging mount rather than a dual EQ/Alt-Az system.
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Aluminum carrying case included. A fitted case protects the mount during transport.
What the Encoder Changes
Strain-wave gearing is what allows the HEM44 to carry several times its own weight without requiring a conventional counterweight system.
The tradeoff is relatively large periodic tracking error compared with a precision worm gear. On the standard HEM44, an external guider has to react quickly enough to follow those changes.
The HEM44EC adds a high-precision encoder directly to the RA axis. Instead of waiting for a guide camera to detect every tracking error after it reaches the image, the encoder continuously measures RA motion and allows the mount to correct much of that error internally.
iOptron calls this Real-Time Periodic Error Correction, or RPEC.
The company says the encoder can reduce the remaining RA periodic error to a few arcseconds and can make unguided imaging practical at shorter focal lengths.
That does not mean the encoder eliminates every tracking error. Polar misalignment, atmospheric refraction, flexure, and other slow errors still exist, and declination is not encoder-controlled.
The more useful way to think about the EC version is that it gives the guider a much cleaner RA platform to work from.
Longer Guide Exposures
This is one of the most useful advantages of the HEM44EC, particularly with longer-focal-length telescopes.
iOptron notes that a conventional non-encoder strain-wave mount may need guide exposures around 0.5 second so the guider can keep up with the relatively rapid RA tracking error.
That can be problematic with an off-axis guider. A faint guide star may simply not provide enough signal in half a second.
The HEM44EC changes that relationship. Because the encoder is already correcting the faster RA behavior internally, iOptron says guide exposures in the neighborhood of 5 to 10 seconds can often be used. The external guider can then concentrate on slower errors such as polar-alignment drift, atmospheric refraction, and flexure.
There is no requirement to use exactly 5 or 10 seconds. Seeing, guide-camera sensitivity, telescope focal length, guide-star brightness, and the rest of the imaging system still determine the best setting.
But it means an OAG on a long-focal-length telescope no longer has to choose between a faint guide star and a guide exposure short enough to chase the raw strain-wave error.
RA Guiding and the Encoder
The HEM44EC also provides control over whether external RA guide commands are used.
With RA guiding allowed, the mount accepts RA corrections from PHD2 or another guiding application while the encoder continues working between those corrections.
The hand controller can also filter external RA guide commands, leaving the encoder to control RA while the guider continues handling declination.
Which approach produces the best result depends on the complete imaging system. The encoder is active either way; the setting determines whether additional external RA corrections are accepted.
For most imagers, there is little reason to begin by disabling useful information from the guider. Start with RA guiding allowed, give the system enough time to settle, and judge the result from the actual stars. Experiment with filtered RA guiding later if the particular setup benefits from it.
Unguided Imaging
iOptron says the HEM44EC's encoder can provide enough RA tracking accuracy that some users may choose to image without guiding at shorter focal lengths.
That is a capability worth having, but not one we would treat as a blanket promise.
An RA encoder corrects the RA drive. It cannot correct declination drift caused by polar misalignment, nor can it remove flexure, atmospheric effects, or every other source of movement between the telescope and the sky.
At a forgiving image scale and with excellent polar alignment, unguided imaging can be practical. As focal length increases and image scale gets finer, guiding becomes increasingly useful.
That is particularly relevant to the HEM44 because the mount has enough capacity to carry telescopes considerably longer than a small travel refractor.
For a 115mm or 130mm refractor, an SCT, or another longer-focal-length imaging system, the encoder's ability to improve the starting point for guiding may be more valuable than eliminating the guider entirely.
44 Pounds Without Counterweights
The encoder gets most of the attention on the EC version, but underneath it is still the feature that defines the HEM44: 44 pounds of counterweight-free payload on a 13.65-pound mount head.
That gives the HEM44EC room for larger refractors, compact SCTs, RCs, astrographs, dual-scope systems, and complete imaging trains carrying cameras, filter wheels, focusers, rotators, and guiders.
There is an important qualification to the payload number. iOptron bases the rating on the payload's center of gravity being approximately 200mm from the RA rotation axis, or an optical tube around 220mm in diameter.
A compact 35-pound SCT and a long 35-pound refractor therefore do not present the same mechanical load to the mount. Tube length, diameter, rear-mounted accessories, and wind exposure matter along with total weight.
The optional counterweight system raises the published payload to 55 lb, but it can also be useful with certain demanding configurations below that limit.
Counterweight-free is a capability, not an obligation.
Why iOptron Calls It a Hybrid
The HEM44EC is neither a traditional German equatorial mount nor a dual-strain-wave design.
Right ascension uses strain-wave gearing because that is where high torque and the ability to operate without conventional balance provide the biggest practical advantage.
Declination uses iOptron's spring-loaded worm-and-belt system, which the company describes as backlash-free. Because the telescope can simply be moved forward or backward in the saddle to balance DEC, another strain-wave gear is not necessary there.
The worm-drive DEC architecture also gives iOptron room for stationary through-mount cable management.
The hybrid design is therefore less about using strain-wave technology everywhere and more about using each drive type where its strengths are useful.
This Version Does Not Include iPolar
The H444 is the HEM44EC without iPolar. It does not include a conventional optical polar scope either.
That makes it a natural choice for an imager who already polar aligns through the imaging system. NINA, SharpCap, ASIAIR, PHD2, and other camera-based routines can all provide accurate polar alignment without adding another dedicated camera to the mount.
Accurate polar alignment becomes especially important if you want to experiment with unguided imaging. The encoder corrects right ascension; it cannot remove declination drift caused by a poorly aligned polar axis.
If you prefer iOptron's dedicated electronic polar-alignment camera, the HEM44EC is also available in an iPolar-equipped configuration.
From the Cloudy Nights Community
HEM44EC owners on Cloudy Nights provide a useful reality check on what the encoder does and does not accomplish.
One owner experimented extensively with the RA guiding settings and saw a clear difference in RA behavior depending on whether external guide commands were being accepted. Other experienced members analyzing the guide logs pointed out an important detail: the encoder itself remains active. The setting changes how external RA guide corrections participate in the system.
Guide-log analysis from that discussion showed the encoder substantially reducing the underlying periodic error, but not completely eliminating slower RA drift. Once external guide corrections were allowed to address that remaining error, the mount returned to much tighter tracking.
That is a good illustration of what the EC system is designed to do. The encoder removes much of the fast periodic behavior internally, while an external guider can clean up the slower errors that remain.
Some owners therefore continue guiding the HEM44EC even when the raw encoder performance is already good. That is not a failure of the encoder. It is using two correction systems for two different jobs.
And because iOptron itself recommends long-cadence guiding for the EC model, continuing to guide does not mean treating the HEM44EC like the standard non-encoder mount.
Power-Down Memory
The HEM44EC includes power-down position memory, a particularly useful feature with a substantial imaging system on top.
If power is interrupted, the mount retains its RA and DEC positions. When power returns, it can resume a GoTo slew or continue tracking without requiring you to start the positioning process from scratch.
That does not mean every camera sequence or third-party imaging application automatically resumes after a power failure. It means the mount itself remembers its position.
The electronic friction brake works alongside that feature by stopping mount movement safely rather than allowing an unbalanced payload to swing if power disappears.
No GPS — Time and Site Still Matter
The HEM44EC does not contain its own GPS receiver.
The GoTo system therefore needs accurate date, time, UTC offset, longitude, latitude, and hemisphere information. Those values can be entered manually or supplied through compatible computer or mobile-control software.
The mount should also begin from a correctly registered Zero Position. Its automatic zero-position search makes that straightforward, and Sync to Target can be used after centering an object to improve local pointing.
If the mount consistently points to the wrong part of the sky, check the time, UTC offset, East/West longitude setting, hemisphere, and Zero Position before assuming there is a mechanical problem.
What's Included
- iOptron HEM44EC hybrid strain-wave equatorial mount head
- High-precision RA encoder with Real-Time PEC
- Vixen/Losmandy-D convertible dovetail saddle
- Go2Nova 8409 hand controller
- 6P6C coiled hand-controller cable
- 12V/5A AC adapter for indoor use
- USB cable for mount control
- Aluminum carrying case
Not included: tripod, counterweight shaft and counterweight, or iPolar electronic polar scope.
Frequently Asked Questions
What does the EC version add to the standard HEM44?
The HEM44EC adds a high-precision encoder to the right-ascension axis along with iOptron's Real-Time Periodic Error Correction. The basic hybrid drive, payload capacity, hand controller, and major mechanical features remain the same.
How much does the encoder reduce periodic error?
iOptron says the high-precision encoder can reduce the RA periodic error to a few arcseconds. The exact remaining error depends on encoder resolution and the complete system, so it should not be treated as a guarantee of a particular imaging result.
Can I image without guiding?
Potentially. iOptron says the HEM44EC is capable of unguided imaging at short focal lengths. Whether that works for a particular system depends on focal length, pixel scale, exposure length, polar alignment, payload, flexure, seeing, and the image quality you require.
Why would I guide an encoder-equipped mount?
The RA encoder handles much of the faster periodic tracking error. An external guider can then correct slower errors such as polar misalignment, atmospheric refraction, flexure, and residual drift. The two systems complement each other.
Can I use longer guide exposures with the HEM44EC?
Yes. iOptron specifically says high-precision encoder models can often use guide exposures around 5 to 10 seconds, compared with much shorter exposures commonly used on non-encoder strain-wave mounts. This can be particularly useful with an off-axis guider.
What does the RA guiding filter do?
It controls whether external RA guide corrections are accepted. The high-precision encoder continues operating either way. Filtering RA guiding leaves RA correction to the encoder while the external guider can continue correcting declination.
How much can the HEM44EC carry without a counterweight?
iOptron rates it for 44 lb (20 kg) without a counterweight. The rating assumes the payload center of gravity is approximately 200mm from the RA axis, so telescope geometry matters along with total weight.
How much can it carry with a counterweight?
With the optional counterweight system installed, iOptron recommends a maximum payload of 55 lb (25 kg) with a 10 lb counterweight.
Does this HEM44EC include iPolar?
No. The H444 is the HEM44EC without iPolar. The HEM44EC is also available in a factory iPolar-equipped configuration.
How do I polar align it without iPolar?
Most imagers use a camera-based routine through NINA, SharpCap, ASIAIR, PHD2, or similar software. The Go2Nova system also provides iOptron's Polar Iterate Align routine for users who do not have a view of the celestial pole.
What is the difference between the HEM27 and HEM44?
Both use the same general hybrid concept: strain-wave RA and worm/belt DEC. The HEM44 increases counterweight-free capacity from 29.7 lb to 44 lb and provides more mechanical margin for longer, heavier, and more heavily accessorized imaging systems. Telescope geometry should be considered along with total weight.
What is the difference between the HEM44EC and HAE43C-EC?
The HEM44EC uses strain-wave gearing on RA and a worm/belt DEC drive and operates as a dedicated equatorial mount. The HAE43C-EC uses strain-wave gearing on both axes and can operate in either equatorial or Alt-Az mode. Both use a high-precision RA encoder, but the mechanical architecture and intended use are different.
Does the HEM44EC have GPS?
No. Time and site information can be entered manually or supplied through compatible computer or mobile-control software.
Does it work with ASIAIR?
HEM44 owners use the mount successfully with ASIAIR systems. Because ASIAIR driver names and connection methods can change with software revisions, follow the current ZWO and iOptron setup guidance rather than relying on an older product-page driver instruction.
What tripod fits it?
The HEM44EC mounts directly to compatible iOptron CEM40/GEM45/HAE43/HEM44 support systems, including the matched LiteRoc tripod, compatible carbon-fiber tripod, and Tri-Pier. A compatible MiniPier can provide additional telescope-to-tripod clearance.
What power does it require?
The mount uses 12V DC at up to 5A through a 5.5/2.5mm center-positive connection. The included 100–240V AC adapter is intended for indoor use.
Final Thoughts
The HEM44EC takes the feature that makes the HEM44 attractive — 44 pounds of counterweight-free capacity on a 13.65-pound mount head — and adds a much more sophisticated way of controlling the RA axis.
The high-precision encoder and Real-Time PEC substantially reduce the periodic tracking error of the strain-wave drive. At shorter focal lengths, that can make unguided imaging practical. At the longer focal lengths the HEM44 is capable of carrying, the encoder may be even more valuable because it allows the guider to work at a slower cadence instead of constantly chasing the raw strain-wave error.
This H444 version leaves out iPolar, so it makes the most sense for an imager who already has a camera-based polar-alignment routine.
If your imaging system has outgrown the smaller HEM27 class, but you still want a mount light enough to carry easily and an RA axis that does much more of its own correction, that is the reason to choose the HEM44EC.
