AM5N Guiding/Tracking Issues??

This is an AM3, but as far as I gather parts are somewhat shared, most notably AM5(N) having nema 14 motor for Dec and Nema 17 for RA, but for Am3 both are nema 14, I think RA DC brake is the same for all models

Martins Vilcins · Oct 8, 2025, 05:24 PM

This is an AM3, but as far as I gather parts are somewhat shared, most notably AM5(N) having nema 14 motor for Dec and Nema 17 for RA, but for Am3 both are nema 14, I think RA DC brake is the same for all models

My mistake, had to backtrack a bit there to find your post again. I think this does reinforce that ZWO’s AM line does have quality control issues across the portfolio. Perhaps the early release models that were tested for reviews had better quality standards that later models didn’t. I would be interested to see if reviewers who purchased their AM mounts have similar issues that have been touched on in this thread now.

I have another update…

Unfortunately the replacement AM5N I received (about a month ago) appears to have been DOA and I didn’t know because I was using scopes with too coarse a pixel scale to tell when I first got it. I just put my main rig on it to run this weekend and noticed some extremely bizarre behavior. At first I thought every sub was trailing because of scope optics, my collimation may have slipped for example.

After the meridian flip, every single sub being trailed stopped. I began to see sharp subs much more often than trailed ones (though it still had its fair share of trailed ones). I spent most of that night tuning the guiding settings and nothing worked to resolve what I was seeing.

TLDR: The harmonics of the RA on this copy appear to be bad. There is an extremely high frequency, high amplitude oscillation being transmitted into the RA drive, which subsequently causes ±1” spikes on the low end, and I saw up to ±8” spikes over and over last night. These spikes are occurring every half second at the bare minimum. It isn’t seeing because my subs trail regardless of how long or short my guide exposures are. This is a problem with the RA drive.

I’ve already contacted the tech I was talking to before, and he suggested the harmonics could be bad, and my testing the previous two night corroborate it. I honestly don’t know how likely this is, it seems incredibly unlikely if the “bad“ unit figures are are low as has been theorized on this post. What I can say is that I have extremely low faith in the ZWO AM5N now. They seem to have made a colossal design flaw with either their choice of harmonics or their stepper motors.

bigCatAstro · Oct 8, 2025, 08:01 PM

Shawn Thiessen · Oct 8, 2025, 07:49 PM

Unfortunately the replacement AM5N I received (about a month ago) appears to have been DOA and I didn’t know because I was using scopes with too coarse a pixel scale to tell when I first got it. I just put my main rig on it to run this weekend and noticed some extremely bizarre behavior. At first I thought every sub was trailing because of scope optics, my collimation may have slipped for example.

It really seems that there was a quality issue that arose between the original run of the AM5s to the AM5Ns.

From all of the issues detailed in this thread alone to the other astronomy sites, ZWO seems to have had a quality leak of units that reached the market and are in their current inventory. Whatever the cause of the leak, known or unknown, it certainly appears to be real and present. Was the replacement unit “new” as in PE tested this year?

I do think that the number of problem units is still small, but not as small as what was disclosed (of course why disclose a larger issue).

I agree though I am not so sure it was a slip. It may be a production issue across the timespan of the production of this model, and they were and still are not aware of it.

It is new as in tested in May, the same month my last AM5N first acted up during. I am not sure what this mount was doing, sitting in ZWO's stock for 4 months, but it appears to have had no good effect on the mount if it ever did leave the factory in a functioning condition.

The issue at heart appears to be fundamentally different as far as the most concerning symptoms, but what is similar between this failure and the last is that the accuracy of the mount depends greatly on the side of the pier. Such findings alone with those we have seen time and time again in this thread, other threads, and my own mount before this one. It's all very strange if you ask me. Both of my copies were and are unable to track in the eastern half of the sky whatsoever. Trying is a waste of time. Rendering the mount only mostly usable in the western half of the sky.

Shawn Thiessen · Oct 8, 2025, 08:44 PM

bigCatAstro · Oct 8, 2025, 08:01 PM

Shawn Thiessen · Oct 8, 2025, 07:49 PM

Unfortunately the replacement AM5N I received (about a month ago) appears to have been DOA and I didn’t know because I was using scopes with too coarse a pixel scale to tell when I first got it. I just put my main rig on it to run this weekend and noticed some extremely bizarre behavior. At first I thought every sub was trailing because of scope optics, my collimation may have slipped for example.

It really seems that there was a quality issue that arose between the original run of the AM5s to the AM5Ns.

From all of the issues detailed in this thread alone to the other astronomy sites, ZWO seems to have had a quality leak of units that reached the market and are in their current inventory. Whatever the cause of the leak, known or unknown, it certainly appears to be real and present. Was the replacement unit “new” as in PE tested this year?

I do think that the number of problem units is still small, but not as small as what was disclosed (of course why disclose a larger issue).

I agree though I am not so sure it was a slip. It may be a production issue across the timespan of the production of this model, and they were and still are not aware of it.

Yes, it certainly could be that this is true and ZWO could still be totally unaware of the problem. However, on the ZWO board, it does appear that ZWO is aware that something with the mount’s hardware is wrong—they just haven’t disclosed the where or what.

AstroCapture325 · Oct 8, 2025, 09:18 PM

That is really disappointing about the performance of the “newer” production model. My AM5N is hanging in there. Its got about 500 hours on it and I will get 2” RA spikes every now and then, but nothing that is affecting my subs (yet).

No kidding. My original model which was apparently supposed to be the worst they put out had performed as well as or better than people woth EQ6-R Pro's. It was tracking so precisely I could barely believe what I was seeing.

All until that fateful night at the end of May.

Yeah I am… indescribably upset about sending away my original one for one which looks far more hopeless. My best choice is to follow up with the tech and get the harmonics replaced. That is my best option so far. I guess if I do that, the periodic error report that came with this mount is null and I won't have an idea of how well it performs on its own. I really hope your's can pull through man. They're really good when they work, and really, really bad when they don't.

bigCatAstro · Oct 9, 2025, 03:04 AM

I’ve already started planning a back-up option with an IOptron CEM40 or something. The whole appeal of a strain wave mount, for me anyway, was how light they are since I have to reset my mount every session (unless I have consecutive nights of good weather).

The draw for me was the portability and promise of low and consistent RMS from reviews. My first one matched that for 8 months and I was happy the whole time. I decided to purchase a local, used EQ6-R Pro a week after I sent me original AM5N back to ZWO. I was incredibly impressed by the performance on the very first night, and then it had issues from then on. This mount definitely has a lot of potential but it spent 3 years outside, no maintenance, no tuning. It needs some love, so I have torn it down to do the SKF bearing replacement and to regrease the whole thing. I knew going into this that the mount was going to need a rebuild imminently. I think once I have the mount reassembled by the beginning of next week, I won’t be as concerned about what happens with this AM5N situation.

I actually got the EQ6-R as a contingency plan for if I was to have another AM5N failure, and coincidentally, it was me blowing the mount up (the EQ6-R) into about 35 pieces in my front room that made me find out this AM5N was not good either. It was honestly really bad timing and I am in the middle of the longest clear sky streak I have seen all year. I couldn’t be more unlucky, I guess. Unfortunately, like both of my AM5N’s, the EQ6-R had a side of pier based issue with the RA as well, but it manifested in the opposite side of the sky and went away after a while. This particular issue has been evading me which is what prompted me to rebuild it.

Do you know if this response was from ZWO China or ZWO USA?

I received my replacement a couple of weeks ago. I finally got a good long clear night to do a more systematic test. I also see worse guiding before meridian than after meridian. Don’t know if the problem is mechanical or can be fixed with firmware. I can imagine the asymmetry in the RA system because pulling the gear up (east of the pier) and slowly lowering the gear down (west of the pier) are different. But I have a hard time imagine why DEC guiding also got worse.

Here is the detail of my test. I point the scope at 10 different coordinates, 5 on each side of the meridian. The DEC angle is 60, 45, 30, 15, or 0 degrees. The starting hour angles is approximately -2.1hr or +2.2hr. The guiding lasts 20 minutes at each location. The rms and peaks are summarized below:

📷 image.pngAs you can see that the guiding before meridian is pretty bad except for DEC=60 and 45 degrees (but for 45 degrees, there are periods of bad guiding. See plots below). After meridian, the guiding is pretty good. Below are the guiding graphs of the 10 sessions. They are shown in the same scale for comparison.

📷 image.pngI then run a long guiding session at DEC=15 degrees from 2 hours before meridian to 2.7 hours after meridian. Here is the result.

📷 image.png

Shawn · Oct 13, 2025, 12:31 AM

I received my replacement a couple of weeks ago. I finally got a good long clear night to do a more systematic test. I also see worse guiding before meridian than after meridian. Don’t know if the problem is mechanical or can be fixed with firmware. I can imagine the asymmetry in the RA system because pulling the gear up (east of the pier) and slowly lowering the gear down (west of the pier) are different. But I have a hard time imagine why DEC guiding also got worse.

Here is the detail of my test. I point the scope at 10 different coordinates, 5 on each side of the meridian. The DEC angle is 60, 45, 30, 15, or 0 degrees. The starting hour angles is approximately -2.1hr or +2.2hr. The guiding lasts 20 minutes at each location. The rms and peaks are summarized below:

📷 image.pngAs you can see that the guiding before meridian is pretty bad except for DEC=60 and 45 degrees (but for 45 degrees, there are periods of bad guiding. See plots below). After meridian, the guiding is pretty good. Below are the guiding graphs of the 10 sessions. They are shown in the same scale for comparison.

📷 image.pngI then run a long guiding session at DEC=15 degrees from 2 hours before meridian to 2.7 hours after meridian. Here is the result.

📷 image.png

Not going to lie, looks very similar to what would happen if you took what my original copy did after the board replacement did, and what my current copy is doing. I am surprised you got a bad replacement too. This is certainly concerning.

Shawn Thiessen · Oct 13, 2025, 09:28 PM

bigCatAstro · Oct 13, 2025, 12:37 AM

I think you should post this to the ZWO Board. There’s something wrong with their run of models post Nov. 2024 it seems like. If the replacement is functioning this way, then they must have changed something in their build process or quality review. I’m already starting to look elsewhere, like the iOptron HEM27EC EQ.

I wholly agree, it looks like they changed something in production post 2024 and that the quality of their AM5N’s has significantly degraded. I am very worried about the prospects of this happening. I am very much of the mind that I think they should do a recall. A 2.5k USD mount should not be doing this, EVER. This is unacceptable.

Oh yeah, ZWO tried to blame my present issue on their 2600 fan vibration issue, when I own a Touptek 2600 and I didn’t have the cooler on. I recorded some videos of the guiding I was getting, and that’s the conclusion they reached… I am speechless. This happened because the ZWO USA tech I was talking to handed me off to the Chinese unit.

Yes, it’s really too bad that something like this is/has occurred. Especially, with the replacements having issues as well. ZWO must have gone with different component suppliers or something between the AM5 and AM5N. Something had to have changed.