HEM27 w/ Carbon Fiber Tripod

SKU: H272A + 8061

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  • $1,998.00
  • Regular price $2,316.00

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Free iOptron Carbon Fiber Tripod included with purchase of the HEM27 or HEM27EC!

Introducing the HEM27 and the HEM27EC, iOptron’s revolutionary hybrid harmonic drive mounts. These light weight, high payload tiny titans will deliver an astronomy experience like never before. Imagine a mount head weighing in at 8.15lbs with a payload capability 29.74lbs, without needing a cumbersome counterweight or shaft. Applying iOptron’s multi decade experience creating precision mounts, the HEM27 brings this vision to reality.

Utilizing state of the art harmonic drive technology for the RA movement in tandem with backlash-free DEC worm/belt drive design, the HEM27s deliver unparalleled weight to payload efficiency. Its black anodized all metal CNC machined body is not only appealing to the eye, it’s a rugged platform that will perform at the highest level for many years to come. Unique features such as an electronic friction break and power down memory allow the mount safely stop and resume a GoTo slew or continue tracking even after an abrupt power loss (No need to realign and start from the beginning).

The HEM27 is available with iPolar electronic polar scope, or with no polar scope if you have your own polar alignment system, such as through an ASIAIR.

The HEM27EC features a high precision RA axis encoder that delivers incredible tracking accuracy, enough that many will choose to image “sans” guiding.

What differs the HEM27 from other strain wave mounts in its category?

HEM27 is very different from other strain wave mounts in its category. HEM27 is hybrid strain wave drive mount; DEC is backlash free worm/belt drive while RA strain wave. If light weight is a primary reason for choosing a strain wave mount, HEM27 is about one third (4 lbs) lighter than the AM5, while about one lb better on payload. HEM27 has a cable management system and PEC function while AM5 has none. Cables of HEM27 are on a stationary platform (no moving/no wrapping), while cables of AM5 rotate with the mount. When power off, telescope/payload on HEM27 stays still while AM5 suffers from scope free swing on DEC.

HEM27 is almost the same weight and payload capability as RST-135, but less than 50% the cost ($1888 vs. $3895), and HEM27EC 40% less than the RST-135E ($3248 vs. $5495). The price of HEM27 and HEM27EC includes V/D dovetail saddle while RST-135/RST-135E does not. Some features with HEM27 are not available with RST-135, i.e., cable management system, power off brake, power-down memory, PEC, no moving/no wrapping cables, etc. However, RST-135/RST-135E comes with GPS while HEM27/HEM27EC does not.

Why HEM27EC and how does it function?

Since the strain wave drive is intrinsically with high PE (2-10 times higher than worm gears), autoguiding with short exposure is essential, or a high precision encoder on RA can bring the PE down to a few arc sec. When a high precision encoder is used, the periodical error is corrected in real time by the encoder, or so-called RPEC, and the amplitude of the remaining error is solely dependent upon the encoder accuracy/resolution.

The high precision encoder used in HEM27EC is the same as in CEM26EC/GEM28EC and should be able to reduce the mount PE significantly, to a level similar to CEM26EC/GEM28EC, and capable for imaging without autoguiding for short focal length.

When guiding strain wave gears, short exposure, e.g., 500ms, is usually suggested. Such short exposure is not sufficient for most stars; hence, it would prevent OAG guiding. However, high precision encoder version often produces the best results with long-cadence guiding, mostly to guide out the low-frequency errors, such as polar alignment error, atmospheric refraction, and flexure, and let the high precision encoder keeping the mount on track. Therefore, with high precision encoder, much longer exposure can be used when guiding, e.g. 5 to 10 seconds. This is especially useful for OAG guiding.


  • Advanced harmonic drive technology
  • Payload capacity of 13.5 kg (29.7 lbs) with the mount weight of 3.7 kg (8.15 lbs)
  • CNC machined and cast metal body
  • Unique friction brake to safely stop movement during a planned or unplanned power interruption
  • 360 second gear period
  • Permanent periodic error correction (PPEC)
  • Go2Nova® hand controller with ~212,000 object database
  • Cable management system, no hanging exterior cables to moving parts
  • Dual saddle (vixen and losmandy-D styles)
  • Built in zero position search and locator
  • Power down position and location memory
  • Integrated ST-4 autoguiding port
  • Built-in Wi-Fi (via hand controller)
  • USB port for firmware upgrade and computer control
  • Soft carrying case
  • Two year warranty
Mount Hybrid Equatorial Mount
RA Gear system StrainWave 17 (RA)/worm gear (DEC)
DEC Gear system Backlash-free worm/belt system
RA reduction ratio 120
Payload w/o CW * 29.14 lbs (13.5kg)
Mount weight 7.49lbs (3.4kg) w/o dovetail saddle, 8.15 ls (3.7kg) with dovetail saddle
Payload/Mount weight 3.65
Period 360 second
Drive motor Stepper motor
Structure Material All metal, CNC machined
Exterior finish Anodized black
PEC Yes, Permanent PEC
Latitude adjustment range 15º ~ 65º
Azimuth adjustment range ± 5º
Polar Scope No
Level indicator Level bubble
Control system GOTONOVA/Commander
Hand Controller Go2Nova® 8409 with ~212,000 objects database
Tracking Automatic
Maximum slew speed 6º/sec
Power consumption 0.5A(Tracking), 1A(GOTO)
Power requiremention 12V DC, 5A
AC adapter 100V ~ 240V (included, indoor use only)
Power off brake Electronic friction brake
Power-down memory Yes
Wi-Fi Built-in
Communication port Yes (Wi-Fi and USB)
Autoguide port Yes (ST-4 compatible)
Firmware upgrade Yes
Tripod Optional
Operation temperature -20ºC ~ 50ºC (hand controller -10ºC ~ 40ºC)
Warranty Two year limited
* 200mm, with payload center of gravity to the RA rotation axis. Or an OTA size of ~220mm.