Servo Direct Drive & High Load


Now available

LBN576/Abell85 – By WD-20

WARPDRIVE-Precision Mount based on Patented Servo Direct Drive Technology

No additional reducer(Belt/Planetary gear) except for Harmonic Drive-Eliminates Assesmbly Errors & Backlash for Enhanced Precision


Less Weight, More Load

Weeight: 5.4kg Load(without CW): 22kg@20cm RA/50NM

After first Servo Direct Drive harmonic mount WD-17S launched by WarpAstron,New WARPDRIVE WD-20 is available now – High Load & Precision as always.

WD-20 based on WarpAstron’s core Servo Direct Drive technology. Type 20 high load starin wave reducer(harmonic drive) for RA axis. Standard Load capacity up to 50NM or 22kg@25cm from RA axis without counterweight. WD-20 can easily handled 6-inch APO refractor, C11 etc. Average guiding accuracy within 0.5″ RMS. The only limit for outdoor astrophotography is not its load capacity – but what your hand can lift.

New designed main body with high power density servo motor, significantly boosting load capacity while keeping its weight only 5.4kg, even lighter than most harmonic mounts with lighter Type 17 reducer. New innovative base design ensures effortless and precise adjustments.


Different period error value, Same level guiding accuracy.

The Servo Direct Drive ensures precision guiding at same level. Not all “random” performance caused by PE – Additional reducer, more assembly error/backlash.

*Stain wave reducers with different PE used in above tests, all tested at same load:28NM, 14kg@20cm from RA axis .


WarpAstron’s WD-17S and WD-20 use servo with high precision encoder as input of stain wave reducer(harmonic drive), servo directly connected with reducer via a shaft for both DEC & RA.

Most harmonic drive mount will use additional reducer like timing belt or planetary gear before strain wave reducer. Thought very few mount will also use direct drive, its motor still be stepper which have issues on loss of torque when operating at high micro-step mode or imprecise positioning.

No additional timing belt/planetary gear used in our mount. The mount’s guiding correction accuracy and performance benifit a lot with this extreme low bachlash drive solution. No need of maintenance for belt which may be impact by aging or low temperature.

Planetary gear/Timing belt

We all know that planetary has large backlash due to its structure, even 3~5 arcmins for high precision planetary which already much expensive.

Though timing belt has no backlash like planetary gear, belt require strictly adjustment for its tension – too large tension may cause overload, while less tension will result in shaping, lead to untimely response during guiding correction. What’s more, the tension will be changed with belt aging and temperature. It require maintenance and adjustment to stay in good tension level for ideal mount performance.

The strain wave reducer has much advantage on its low backlash(<10″), which even been called “zero” backlash. but mount’s guiding accuracy based on system transmission error, not only SWR’s periodic error – the transmission/assembly error introduced by additional belt/planetary gear could be several times greater than SWR’s PE.

Direct Drive

WARPDRIVE Mounts’ servo motor directly connected to input of strain wave reducer via a simple shaft. No backlash/transmission error existed between servo and SWR, with the advantage of high transmission efficiency.

And we use special designed servo with high precision encoder instead of stepper for both axises. Servo can provide constanly torque in whole RPM range, without torque loss issue like stepper. Our servos based on BLDC motor and have no reducer struction inside it – Direct and strong power input for mount. High precision encoder support the motor response quickly and precisely to guide correction, and less sensitive to load change.

Based on feedbacks from our users, WARPDRIVE mount benifit a lot based on its servo direct drive – precise and responsive to guide correction, the average guiding performance can easily get to 0.3~0.5″ RMS. Depending on guiding system sampling level(Typical 1 second exposure).

Detail refer to PHD2 log examples on our website, provided by our users.

Mount’s load capacity depend on BOTH load weight and moment the force. It’s more precision to talk about torque not simple weight. Torque(Nm) = Load Weight(kg) * Moment (m). Below for GEM mode:

WD-20 can handle 50NM without counterweight, equal to 20kg load at the 25cm from RA axis.

WD-17S can handle 38NM without counterweight, equal to 15kg load at the 20cm from RA axis.

Please noticed that even your load with in the capacity of mount, you still need to use properly pier/tripod to improve stability of whole system, and also use couterweight properly to balance the tripod to prevent it falling or other safety issue. Good tracking and guiding performance rely on both mounts and tripod/pier.

All our mounts support both GEM and Alt/Az mode. Altitude adjustment range from 0~90°. You can switch the mode via Hand controller.

Our mount can work well lower to -25°C~30 °C.

Direct drive is much reliable in extreme low temperature. No need to worry time belt maybe shaping even torn in low temperature.

Both WD-17S and WD-20 have special heating design by brake. Brake device can provide additional heating for improve operationg condition for SWR. If user require extreme low temperature below -25°C, please ask our Customer Support for firmware update.

Thanks to OnStep Community, our mounts can support most frequently used software basedon NINA or INDI driver, such as NINA, Kstars, or astro computer like Stellarmate, ASIAIR.