FAQ: More Information about HEM44

Q & A about HEM44
  1. What does the HEM44 name mean?
    The H stands for Hybrid and Harmonic (Strain Wave gear), EM for Equatorial Mount. 44 refers to the payload of the mount (without a counterweight), 20 kg or 44 lbs.

  2. Why Hybrid? Is there any advantage/disadvantage?
    The most important and attractive feature of strain wave mount is going counterweight-less for grab-n-go. Strain wave gear works well at imbalanced condition, therefore, a mount made from strain wave gears does not need a CW. Naturally, no CW is necessary on DEC for any equatorial mount, since the payload (telescope) can slide forward/backward easily to achieve self-balance. On the other hand, worm gears naturally have much better PE than strain wave gears, and unlike the solid piece of strain wave gears, the hollow shaft of worm gear structure makes cable management possible. So, a hybrid mount combines the advantages of strain wave and worm gears and can achieve counterweight-less at lower cost. We can then put the savings on to some important features, such as the cable management system and electronic polar scope.

    Strain wave gear has negligible backlash while worm gear varies; some designs without spring loading might have large backlash and others with spring loading backlash free. The DEC unit of HEM44 utilizes belt and spring-loaded gear to achieve zero backlash.

    iOptron might be the only company in the strain wave gear mount business who has a track record making quality and precision telescope mounts (iOptron and its prior entity has a 30-year track record of dedication on telescope mounts, and only telescope mounts). Our design of hybrid strain wave/worm gear is logical and practical with the balance of quality, performance, and price.

  3. What differs the HEM44 from other strain wave mounts in its category?
    HEM44 is very different from other strain wave mounts in its category. HEM44 is hybrid strain wave drive mount; DEC is backlash free worm/belt drive while RA strain wave. HEM44 has a cable management system and PEC function while none with other brands. Cables of HEM44 are on a stationary platform (no moving/no wrapping), while cables of other brands rotate with the mount. When power off, telescope/payload on HEM44 stays still while some of other brands suffers from scope free swing on DEC or both axes.

  4. Why HEM44 does not come with a GPS?
    HEM44 comes with WiFi. When Commander Lite is in action (WiFi version ASCOM), a GPS module is redundant; one may easily import the GPS info from a smartphone to the mount/hand controller. There is no worry about lacking internet, WiFi, and cell phone signals in rural areas; Commander Lite can always get GPS info from a smartphone to the HEM mount/hand controller, no dead corner.

  5. Why HEM44 is EQ only, will AZ be an option in the future?
    HEM44 is designed as a dedicated EQ mount since the high intrinsic PE of strain wave gear can only be suppressed by autoguiding or high precision encoder. Autoguiding and high precision encoder are not economically feasible for AZ mode. On the other hand, HEM44 comes with cable management system, and AZ mode might compromise the cables through the mount. A multi-function/mode mount sounds good, but there are some compromises to either mode that would prevent the mount to perform the best at either mode. Between dual mode and cable management function, we have chosen the latter and believed the best interest for the majority. As a matter of fact, the cost of making HEM44 EQ only is almost the same as making it AZ/EQ dual mode.

    We are introducing dual-axis strain wave models, HAZ31 and HAZ46, as dedicated AZ mounts, primarily for large binoculars and for satellite tracking. Counterweight-less is especially attractive for large binoculars since balancing bino with a traditional AZ mount is really challenging. HAZ comes with “Level n Go” function, same as AZ Mount Pro, customers only need to level the mount and power on, the mount can automatically calibrate the directions and ready to goto and tracking.

  6. Will iOptron make dual strain wave gear EQ/AZ mount?
    Yes, we are introducing HAE series strain wave gear mounts, HAE29/HAE29EC and HAE43/HAE43EC. HAE models are EQ/AZ capable, good for 0-90 latitude. Differ from other brands, HAE series are pass- through channel ready for customers putting their cables.

  7. Why HEM44 does not come with PE spec?
    Since the PE of any strain wave drive mount is dictated by the strain wave gear, which is from 3rd party, and dependent on payload, position, and imbalance condition, we don't spec the PE of HEM44 and believe any PE value is inappropriate. On the other hand, almost all strain wave gear mount manufacturers use similar or identical strain wave gears, so one may reference any other mount which comes with a PE value (though we doubt its meaningfulness).

  8. Why HEM44EC and how it functions?
    Since the strain wave gear 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 (Realtime PEC) and the amplitude of the remaining error is solely dependent upon the encoder accuracy/resolution.

    The high precision encoder used in HEM44EC is the same as in CEM40EC/GEM45EC and should be able to reduce the mount PE significantly, to a level similar to CEM40EC/GEM45EC, and capable for imaging without autoguiding for short focal length.

    When guiding strain wave gears, short exposure, e.g., 500 ms, 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, flexure, etc, 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.

  9. What payload HEM44 can undertake with CW applied?
    HEM44 is designed to handle imbalanced payload on RA, up to 20kg/44lbs. It can also receive optional counterweight for higher payload. We recommend no more than 25 kg payload with a 10lbs CW attached.

  10. Can an HEM44 be controlled by a computer?
    HEM44, as other iOptron mounts, can be controlled by:
    (1) Windows PC via ASCOM/iOptron Commander, through USB or WIFI
    (2) MacOS via direct control/plug-in (SkySafari/The Sky X), or third party INDI driver
    (3) iOS via iOptron Commander Lite, SkySafari Plus/Pro through WIFI connection
    (4) Android via iOptron Commander Lite, SkySafari Plus/Pro through WIFI connection
    (5) Raspberry PI via third party INDI driver

  11. What tripod, pier extension and adapter available for HEM44/HEM44EC?
    HEM44/HEM44EC can seat directly on the CEM40/GEM45 tripod and Carbon Fiber Tripod (8061), They can also seat on a Tripier (8034).

  12. Is there an HEM version suitable for low latitude near the equator?
    Yes, we have special version HEM44 and HEM44EC designed for low latitude, 0-22 degrees. They are immediately available at our factory. Special order in USA with 2-month lead time.
    H442L, Low latitude HEM44
    H442AL, Low latitude HEM44 with iPolar
    H444AL, Low latitude HEM44EC

HEM44 Autoguiding
(HEM44 mount, payload 11kg, FL 530mm, iCAM464C guiding camera with exposure 500ms, 12 minutes guiding)