Warpastron WD-20 vs. ZWO AM7?

Since the overall design is almost similar to the AM5 in both shape and size, I really question the mount’s ability to hold it’s stated capacity and perform, especially with the moment arm being so small.

If I’m being honest I would not trust a harmonic mount for high-payload operations simply due to the mount weighing less than the tube. More stress on the system’s pivot points over time.

Maybe take a look at the UMi20 by Proxisky.
The mount is similar to the WD20 but has some nice improvements, such as no clamping on the PA mechanism.
I like my UMi20 a lot.

Also, the AM7 load capacity of 20 kg is measured at 20 cm from the axis.
The AM5/3 are measured at 25 cm, so when you make a direct comparison at 25 cm, the AM7 is much closer to the AM5N.
There is a nice thread on CN about this.

My concern is escaping the ZWO sphere of software. The choice to me is: Do you want to be a prisoner of their software, or not?

I’ve chosen not. I do have 3 of their cameras. But after an experience with their service department, I’m heading away from ZWO.

As for Harmonic mounts in general, I think they have potential, But I don’t think they are as good as they could be. They need to improve their tracking and guiding numbers.

Olivier Constans · Feb 12, 2026 at 11:14 PM

Kartik Atre · Feb 10, 2026, 02:51 AM

Hey good people,

Anyone awaiting ZWO AM7? How do you think it will compare with Warpastron WD-20?

CS,

Kartik

Hello,

I have an AM5N, a WD-20, and a WD-20P. I won't be buying from ZWO again because, compared to Warpastron, the AM5N is very inaccurate in terms of altitude adjustment, which makes polar alignment difficult. I get better tracking results with the WD-20 than I ever did with the AM5N.

I use the WD-20 with 20kg RC10s and a 5kg counterweight. The total load capacity of the WD-20 is 35kg (OTA + counterweight). Thanks to a formula provided by warpastron, which gives the OTA torque - counterweight torque < 57 Nm, I estimated that a 25kg tube (a big tube for an OTA of 300mm diameter , including the optical train) can be placed on the WD-20 with an 8kg counterweight. This could correspond to an RC12 carbon tube version (18kg). Beyond that, a stronger mount is required. Regarding the AM7, I seem to recall that the motor does not have as much power as those of the WD-20, which must be around 60 Nm of torque, taking into account that if warpastron says not to exceed 57 Nm, it is with a small safety margin so as not to use the motors at their limit. When I used the AM5N with an RC10 that I had lightened as much as possible for a total weight of 18kg including the optical train + 5kg of counterweight, the AM5N, although rated for a maximum of 20kg, had a hard time keeping up, especially in high altitude positions.

That's why I switched to Wapastron. Of course, with OTAs weighing 8-10 kg, such as an RC8, the AM5 works well, if you ignore the difficulty of polar alignment. Personally, I doubt that the AM7 is up to the task of a WD-20.

Thanks Olivier!

That was really helpful. I too have the AM5 (the non-N) and yes, I agree. The altitude adjustment is a pain. Especially when error is asking you for a downward correction. The backlash is huge, and then it overcorrects. I use it for my lighter setups with Askar FMA180 and WO RedCat 91.

You said you had both WD20 and WD 20P. Are there any differences other than power delivery?

Given what has been going with the AM5Ns and the RA motor problems, I won’t be upgrading with ZWO anytime soon. I am interested in the MLAstro SAL-66 as a potential upgrade though whenever it does come out.

Alex Nicholas · Feb 13, 2026, 03:24 AM

SonnyE · Feb 10, 2026, 03:49 PM

As for Harmonic mounts in general, I think they have potential, But I don’t think they are as good as they could be. They need to improve their tracking and guiding numbers.

They certainly aren’t as good as they could be, but people need to stop looking at them like some sort of silver bullet. They are designed for a purpose, and while they CAN perform well with large scopes, and they CAN perform repeatedly in certain scenarios, they are NOT ‘better’ than an equivilantly priced GEM… I moved from a Losmandy G11 Gemini II to a Emcan Astro EM31 Pro harmonic mount because my back is failing as I get older with a few herniated discs, and a few more that are heavily compressed, and carrying a 40kg mount outside was becoming tiresome… My EM31 Pro on its tripod weighs about the same as the G11’s counterweight bar and counterweight… Harmonic mounts are a convenience item, not an upgrade from traditional mount designs.

Friction drive beats harmonic mounts, a quality GEM beats harmonic mounts, and this is not to say that they are ‘bad’ because they aren’t, but their tracking quality is an inherrant property of the strain-wave gear system, their ridiculous periodic error is litterally unavoidable, ±10” peak to peak on the AM5N is good for a harmonic mount, but really, that’s rubbish tracking… and other mounts (including the original AM5 can be as high as ±20” peak to peak… My G11 with precision RA worm measured ±4” peak to peak… So going to a harmonic mount was a downgrade for me, but it meant that I could stay active in astrophotography - so it’s a sacrifice I was willing to make.

Guiding numbers are about the same. the G11 would routinely guide sub 0.6” RNS, and on a good night as low as 0.35” RMS. BUT, the G11 would be making a correction every 15~20s, where as the harmonic mount makes corrections almost every second or two.

If I had a permanent observatory, or a better spine, there’s no way I’d be using a harmonic drive mount…

For most people - under ‘typical’ conditions, the tracking accuracy doesn’t really matter, and the guiding accuracy is MORE than sufficient, however, you certainly won’t see someone set up a rig at a remote observatory with a 10~12” RC or CDK on a harmonic mount any time soon, because the resolution and accuracy required to make those scopes shine simply doesn’t come from harmonic mounts. Even with 0.3~0.4” RMS guide numbers, the fact is that the harmonic mount will be bouncing around all over the place where a friction drive or a quality GEM will be rock solid, providing 5~10 corrections in a 300s sub, vs maybe 200 corrections on the Harmonic mount…

Thank You, Alex. I really appreciate your post. Very detailed.

Sorry about your back. Mine too, degenerative disk disease and just worn out from life and hard work. I just keep my GM811G HD set-up and cover the whole shebang. Works good for me for now. And our 25-year-old Grandson has come and helped me the one time recently I needed to bring the telescope in. So those are my adaptions for now.

Keeping my mount set-up has the advantage of my mount being Pier like with it’s Polar Alignment and repeat performance night after night. Accuracy I appreciate. I explained to Scott Losmandy my plan was to make my mount into a “Portable Pier” configuration with the EXT12 riser. And not am I disappointed. I have my mount assembled so I can break it down into 5 sub-assemblies to move. IIRC, they are all in the mid-30 pounds or lighter. But the 130mm telescope with all the trimmings is running 36 pounds and is a bit too much for my Arthritis in my right shoulder. Waa!

The inability of these Harmonic mounts to handle more than 44 pounds perturbs me. It also makes me think they are coming from one cookie cutter factory because they seem to carry the same disturbing poor tracking and guiding characteristics. Warp Astron does show a 48.5-pound capacity, and it is using DC motors with encoders, not stepper motors. Cuiv states the one Warpastron sent him for review runs absolutely quiet. A good point for so many who complain about the mechanical noise most mounts make. My mount makes some noise, not an objectionable amount by any means. And is virtually silent compared to my neighbors Chevell hot rod he fires up at all times of the day or night. (I don’t have any filters for that.)

Something I picked up in Cuiv’s review was how the base from the ZWO AM5 tripod attaches perfectly to the Warp Astron. 🤔 More fodder for my wondering if these roll out of the same factory like the Synta Corp equipment does. I sleuthed out Warpastron to Shanghai, China So, it is a different factory apparently. And although a new Company, Warp is headed in their own direction. At this point I’d be interested in anyone’s experience with them for warranty repairs. Mine with ZWO has me sworn off anymore ZWO equipment.

So in light of this recent enlightenment, I would think Warpastron WD20 might be worth looking into.

Some links would be in order: Cuiv’s review. And Astro Tube has a very enlightening Polar Alignment video.

Something noteworthy, I notice the adjusters have course threads on them. That seems to run in many of the Asian mounts. I learned how to do fine adjustments with my AVX by basically adding pressure one way or the other when fine tuning that mount. Not so much with my GM811G, it has fine threads in its adjusters. Why Asia still stays with courser threads may have something to say about their confidence in the threads to hold up. But with a little trial and error and learning to finesse the adjustments it should work well.

If I was to be in the market for some sort of Harmonic Mount (I am not) I do believe I’d be getting one of these Emcan Astro EM31 Pro harmonic mount or Warpastron 20. They are simply the better mounts. As for Harmonic mounts.

SonnyE · Feb 13, 2026, 10:42 PM

Cuiv states the one Warpastron sent him for review runs absolutely quiet.

I confirm this, either the WD-20 or the WD-20P makes almost no noise. You can ear a small motor noise when you push the slew speed at the maximum , but even like this is is quite discreat.

Kartik Atre · Feb 14, 2026, 03:27 AM

Thank you all. You have given me a lot to think about.

Cheers,

Kartik

That’s the beauty of forums, lots to think about from many different perspectives.

Enjoy your search and I hope you can find happiness. 😁

A few words to bring my own experience in. I own a Pegasus NYX 101 and I’m prettyb happy with it, up to a certain load. I would say a 100mm refractor works fine, maybe up to 120. When I need heavy barlowing for tiny DS objects, sun spots etc I “muscle” my brand new G11T out. Yes it’s damn heavy… but rock stable and smooth.

SWM design :

Strain wave reducers have a lot of advantage, and some drawbacks :

plus :

• no backlash , permanent tension is provided by the flexspline

• high reduction ratio

• load and torque capability with respect to size and weight

• lifetime

• no maintenance (specially for a mount with a ridiculous amount of accumulated revolutions)

minus :

• linearity (which is pivotal for smooth tracking) is a good as the price you pay for the reducer, there is no magic. Moreover, any defect in the pair flexspline / outer gear with bring some kind of friction torque, which generates tension on the flexstuff… when tension releases, you may have a huge elastic detent torque which is impossible to control which in turn may induce severe tracking errors

• the periodic error is not repeatable across the full angular range

most of the disadvantages are brought by a lower built quality.

Balancing :

As an engineer, I don’t like unbalanced mechanical rotating systems : they bring parasitic torques, dynamic coupling between axes when moving, and they feed on lack of structural stiffness.

So I always balance, as far as I can, the load, let’s say over 8kg.

Dec axis is balanced on an auxiliary free rotating mount with alt-az capability , around ALt axis, or more simply on a table , rolling the bottom dovetail on a flat surface, on a cylindrical stuff placed across the dovetail. Find the balance point and index it.

AD axis , I do it by computation (algebraically summing torques values of various load elements.

Caveat :

1° balance , and record the balancing recipe for each given configuration. Keep in mind that both weight and inertia are to be taken into account : 15kg do not behave the same way in a compact reflector and a long refractor. When using heavy loads, always make sure the AD brake is active.

2° use a stiff tripod or pier, even if it’s a weight cost

3° except when adjusting alt and azimuth, always torque the blocking screws , even during the rotation about AD axis when performing polar alignment : star motion analysis will be altered by mount response to unbalanced load.

tentative conclusion :

Harmonic mounts are wonderful tools, on account of their transportability and ease of use. A general marketing trend in the competition, though, tend to over-sell a little bit load capability.

Kartik Atre · Feb 17, 2026, 05:33 AM

alpheratz06 · Feb 16, 2026 at 11:52 AM

A few words to bring my own experience in. I own a Pegasus NYX 101 and I’m prettyb happy with it, up to a certain load. I would say a 100mm refractor works fine, maybe up to 120. When I need heavy barlowing for tiny DS objects, sun spots etc I “muscle” my brand new G11T out. Yes it’s damn heavy… but rock stable and smooth.

SWM design :

Strain wave reducers have a lot of advantage, and some drawbacks :

plus :

• no backlash , permanent tension is provided by the flexspline

• high reduction ratio

• load and torque capability with respect to size and weight

• lifetime

• no maintenance (specially for a mount with a ridiculous amount of accumulated revolutions)

minus :

• linearity (which is pivotal for smooth tracking) is a good as the price you pay for the reducer, there is no magic. Moreover, any defect in the pair flexspline / outer gear with bring some kind of friction torque, which generates tension on the flexstuff… when tension releases, you may have a huge elastic detent torque which is impossible to control which in turn may induce severe tracking errors

• the periodic error is not repeatable across the full angular range

most of the disadvantages are brought by a lower built quality.

Balancing :

As an engineer, I don’t like unbalanced mechanical rotating systems : they bring parasitic torques, dynamic coupling between axes when moving, and they feed on lack of structural stiffness.

So I always balance, as far as I can, the load, let’s say over 8kg.

Dec axis is balanced on an auxiliary free rotating mount with alt-az capability , around ALt axis, or more simply on a table , rolling the bottom dovetail on a flat surface, on a cylindrical stuff placed across the dovetail. Find the balance point and index it.

AD axis , I do it by computation (algebraically summing torques values of various load elements.

Caveat :

1° balance , and record the balancing recipe for each given configuration. Keep in mind that both weight and inertia are to be taken into account : 15kg do not behave the same way in a compact reflector and a long refractor. When using heavy loads, always make sure the AD brake is active.

2° use a stiff tripod or pier, even if it’s a weight cost

3° except when adjusting alt and azimuth, always torque the blocking screws , even during the rotation about AD axis when performing polar alignment : star motion analysis will be altered by mount response to unbalanced load.

tentative conclusion :

Harmonic mounts are wonderful tools, on account of their transportability and ease of use. A general marketing trend in the competition, though, tend to over-sell a little bit load capability.

Thanks. I have a Nyx-101 too. I am using it on a stable pier with a Celestron C11 and a full Mono setup including external focussed and rotator. Seems to do ok. However, polar aligning this mount is a pain in the backside.. Before I had the pier, it was on a steel tripod and I would lug it every night and polar align. Thankfully, now it’s aligned and ready to go and I don’t have to correct as frequently. Otherwise, it works like a charm.

Thanks again for the detailed explanation. It’s always good to have an Engineer’s perspective over the marketing hype.

Polar Aligning

Back when I first got Sharpcap my reason was for Polar Alignment. One night I got curious and ran about a dozen Polar Alignment routines. (And I’ve retained my subscription for over a decade just for the PA routine.)

Even though nothing had changed from one to the next it was interesting how each one wanted some adjustment. The end result was a great Polar Alignment, and the conclusion was the only variable was the seeing.

A few weeks ago I did a electronic reset on my mount and skipped the PA routine. When building my Modeling (Alignment in Chinese terms) I was pleased at how the stars my mount picked would all land in the view and easily centered with nudges. Further affirming the Polar Alignment was good.

So you could try running a Model (Alignment) routine to confirm your PA for your mount. Even if you don’t, it was interesting to do multiple Polar Alignments to see how the seeing (Atmospheric variations) at each run varies. Even for Pier or Portable Pier (mine) set-ups.

There used to be a Rule of Thumb for Asian mounts, that was to half the advertised capacity they stated for astrophotography. I followed that with my AVX during the 3.5 short years of its troubled lifespan. It had a 30-pound load rating, and I limited mine to 15 or less, total. So I am curious if that advise still applies. Because when reading of difficulties with these harmonic mounts one consistent complaint is when they add more load to them, they become less stable.

I have 3 - Pegasus Astro items (But no NYX). And love them all. So my experience with their equipment has been excellent. I do wonder why all the ones seem to run 44 pounds rating W/O counter weights (Except theUMi 20s at 48 pounds.). And better with adding a counterweight. Why not just add the counterweight to begin with? What is the aversion to counterweights? Once balanced no need to fiddle with it again.

Tony Gondola · Feb 17, 2026, 05:21 PM

I think the adversion to counter weights is with people who have to setup and breakdown every session. For those who don’t, it’s a big nothing burger…

Probably right, Tony.

Whenever I break down my mount, I simply unscrew my counterweight bar with the weights clamped as they are. When reattached, they land in the balance point they were at. Just seems logical to me.

But then, I’ve always used counterweights. So I used them to my advantage.

Kartik Atre · Feb 13, 2026, 02:57 AM

You said you had both WD20 and WD 20P. Are there any differences other than power delivery?

You have to power and PD output in the saddle. It helps a lot because now I don’t need a power switch (I don’t have any dew heater so.. ) . I connect directly the melee 4s with the power data cable from the saddle and the camera with the regular 12v output from the saddle.

Now in terms of guiding, it seems to me that I have better guiding with the 20P. With the 20 my average guiding rate was between 0.55 and 0.7” rms , with the wd-20P it is between 0.45 and .056”. My best guiding with a very good seeing for my place the wd-20 was 0.32” for a duration of 20s , with the wd-20P it was between 0.32 and 0.35 for several minutes. I read that the WD-20P has a more powerfull RA motor and also more precise encoders than wd-20 , maybe this is the reason it work a little bit better.