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The HEM27 is an innovative hybrid strain wave drive mount from iOptron, offering a lightweight and high payload solution for astronomy enthusiasts. The mount features state-of-the-art strain wave drive technology and a backlash-free DEC worm/belt drive design, providing exceptional weight to payload efficiency compared to traditional mounts. It can be controlled through a Windows PC, MacOS software, smartphone, tablet or Raspberry Pi, and the HEM27EC model has a high precision RA axis encoder for exceptional tracking accuracy.

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Introducing the HEM27, iOptron’s innovative hybrid strain wave drive mounts. These lightweight yet mighty mounts offer an unparalleled astronomy experience, with a mount head weighing in at only 3.7 kg and capable of supporting up to 13.5 kg of payload without the need for a cumbersome counterweight or shaft. With iOptron’s decades of experience in creating precise mounts, the HEM27 is the epitome of innovation and performance.

The HEM27s feature state-of-the-art strain wave drive technology for the RA movement and a backlash-free DEC worm/belt drive design, providing exceptional weight to payload efficiency compared to traditional mounts. Its black anodized all metal CNC machined body is not only visually appealing, but also rugged and built to last. The mount also has unique features such as an electronic friction break and power down memory, allowing for safe and seamless operation even after power loss or interruption.

Strain Wave Technology

Harmonic drive or strain wave mounts offer several advantages over typical worm gear mounts for telescopes:

  1. Improved accuracy: Harmonic drive mounts use a flexible metal wave generator and a rigid ring gear to transmit torque. This design provides high accuracy and reduced backlash compared to worm gear mounts, which can have play or slop in their gears.
  2. Higher Load Capacity: Harmonic drive mounts can handle higher loads and have a higher load capacity compared to worm gear mounts, making them ideal for use with heavy telescopes.
  3. Higher Speed: Harmonic drive mounts can rotate faster than worm gear mounts, providing quicker and smoother tracking of celestial objects.
  4. Quieter Operation: The smooth operation of harmonic drive mounts generates less noise compared to the meshing gears in worm gear mounts, making them ideal for use in quiet observing locations.
  5. Longer Life Span: The lack of physical contact between gears in harmonic drive mounts leads to reduced wear and tear, extending the life of the mount compared to worm gear mounts.

Overall, harmonic drive or strain wave mounts offer improved accuracy, higher load capacity, higher speed, quieter operation, and longer life compared to worm gear mounts, making them an attractive option for use in high-end telescopes.

Control Options

The HEM27 can be easily controlled through various devices such as a Windows PC via ASCOM/Commander or a MacOS software through a third-party INDI driver, a smartphone or tablet through iOptron Commander Lite or a SkySafari app, or a Raspberry Pi device through an INDI driver.

iPolar Version

The iPolar variant of the HEM27 has a built-in electronic polar scope for easy and accurate polar alignment.

High Precision Encoder (EC) Version

The HEM27EC variant features a high precision RA axis encoder that delivers incredible tracking accuracy, enough that many will choose to image “sans” guiding. With a high precision RA axis encoder, you’ll enjoy incredible tracking accuracy that many will choose to image without guiding. The high precision Right Ascension (RA) axis encoder in iOptron EC mounts operates by measuring the rotational position of the RA axis with high accuracy. The encoder typically consists of a disk with evenly spaced markings and a sensor that reads the position of these marks as the axis rotates. The high precision of the encoder allows the mount to make these adjustments accurately and smoothly, resulting in improved tracking performance and reduced error.

Weight4 kg
Dimensions30 × 25 × 20 cm

HEM27, HEM27 with iPolar, HEM27EC with Encoder


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MountHybrid Equatorial Mount
RA gear systemStrainWave 17
DEC gear systemBacklash-free worm/belt system
RA reduction ratio480:1
Payload w/o CW *29.74 lbs (13.5kg)
Mount weight7.49lbs (3.4kg) w/o dovetail saddle, 8.15lbs (3.7kg) with dovetail saddle
Payload/Mount weight3.65
Payload with CW *44 lbs (20kg)
Period360 second
Drive motorStepper motor
Structure MaterialAll metal, CNC machined
Exterior finishAnodized black
PECYes, Permanent PEC
Latitude adjustment range15º ~ 65º
Azimuth adjustment range± 5º
Level indicatorLevel bubble
Control systemGOTONOVA/Commander
Hand ControllerGo2Nova® 8409 with ~212,000 objects database
Maximum slew speed6º/sec
Power consumption0.5A(Tracking), 1A(GOTO)
Power requirementionDC12V-5A (5.5/2.5mm DC plug)
AC adapter100V ~ 240V (included, indoor use only)
CableNo moving/wrapping
Cable management2X12V (4A max.), 1X USB2.0
Power off brakeElectronic friction brake
Power-down memoryYes
Communication portYes (Wi-Fi and USB)
Autoguide portYes (ST-4 compatible)
Firmware upgradeYes
Dovetail saddleVixen & Losmandy
Counterweight shaftSS Φ20X200mm, M16 thread (Optional)
Counterweight10 lbs (4.5kg)(Optional)
Operation temperature-20ºC ~ 40ºC (hand controller -10ºC ~ 40ºC)
WarrantyTwo year limited


Polar ScopeiPolar electronic polar scope for the iPolar Variant
High precision encoderYes (RA) for the EC variant

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