Problem with AM5N

Xda3IH99

Recently started experiencing issues with the AM5N, and I'm having trouble nailing down what's happening. I've been running this mount since January, and guiding has been relatively good but over the last few weeks I've been seeing star trails due to an RA correction that is creating trails on 50%+ of my subs.

I started with the default settings on the ASIAIR+, and just changed the exposure settings from 2s to 1s or 0.5s to try and improve guiding. I recently tried with a different guide camera, but the issue still persists leading me to think it's something else.

Everything has been tightened down on the scope and the mount, there is nothing flexing at all. I have placed the tripod (TC-40) on some heavy cinder blocks to stabilize and that has helped significantly when I am tracking on the east side of the pier. Whenever the pier is on the west side, we get these spikes.

Equipment Details:

AM5N
ASIAIR+
ASI2600MC Pro
RedCat 71
ZWO EAF
WO 32 Uniguide 120mm
ASI120MM Mini
ASI715MC (new camera, tried to use this to see if there would be any improvement.

Attached my guiding logs from a good session (2025-03-08 and 2025-03-12), and then from 2 sessions where it just got terrible (2025-03-14 and 2025-03-25)

Link to guiding logs

Polar alignment under 1" using the AA routine, did this twice to ensure it didn't change.
Performed a guiding calibration as close as I could to the meridian and celestial equator, although this is pretty far in DEC (+37.1) since there are a lot of trees on the south side of the telescope.
First target was North + East of the meridian. Within the first 10 minutes, I got the -45" peak on the RA. I have a short video while I was watching the guiding session here. I switched targets and continued guiding, started getting the RA peaks after 15-20 minutes in (max -28.86" peak), video here.
I then switched sides and pointed to a target North + West of the meridian, over an hour of guiding with no RA peaks over 5". Total RMS was 0.97".
After I turned off dithering 2 nights ago, I didn't turn it on to ensure this wasn't causing any adverse effects.

Calibration ran automatically for my Plan, but guiding ran pretty horribly with the max peak around -53.62". I noticed in the graphs that it took about 20 minutes for the first peak to happen and then it just continues with those peaks ₅ minutes. Although, eventually I can see during the session that I get 2-3 additional smaller peaks the longer it goes on. At 03:10 EST, it did the meridian flip and started on the East side of the pier, guided for over an hour at 0.74" RMS with no peaks.

I'm noticing that the issue seems isolated to the west side of the pier. My view from the backyard is strictly north, so my targets are within 2-3h either side of the meridian.

I've made sure the tripod is weighed down with at least 20-25lb weights. The nights I tested there was minimal wind, and no clouds at all coming through.

From the East side of the pier, the guiding is pretty good for me:

From the West side of the pier, the guiding has these very high peaks which guiding attempts to correct:

I reached out to ZWO support last week, and I still don't have a response to any of my queries.

ASIMount-ZWO

Xda3IH99 I'm sorry for the negative experience you had. Did you submit the runtime log in APP?Have you received the analysis of the issue logs?

F5146666

ASIMount-ZWO Can somebody from ZWO please take care of this issue.

There are many people having troubles with sudden RA tracking offsets caused by this mount.

My assumption is here that the sideral tracking rate does not fit to every Mount/Setup and seems to change/drift over time. My issue with the RA motor suddenly snapping back when tracking is activated with my Telescope being on the east side of the pier can currently only be mitigated, when counterweight is being increased way over the 5kg limit.

F5146666

Hi,

I might have a comparable if not similar problem. Here is more or less the information that I already posted in another forum:

Recently I decided to defork my CPC1100 and use the C11 tube on the AM5N. My total setup weight is about 17kg (37.5lbs), using a 5kg (11lbs) counterweight.

I read about RA spike/jump issues of a "couple of people" even before I used the AM5N, but did not dig into this any deeper as not everyone seemed to be affected by this problem including myself. Everything went fine for me with this setup, but those huge RA spikes/jumps started in my last two sessions. RA gets suddenly and repeatedly far off for no obvious reason and PHD2 needs a couple of seconds (if at all) to get guiding numbers back under 2".

I recognized a lot complaints about this and assumptions about the potential root cause. Some people reported that tensioning the belts solved the issue for them (maybe upfront: not for me). But the information that this could lead to a solution and a thread where somebody teared down an AM5 gave me confidence and encouraged me to continue this investigation.

In my case (and I want to emphasize at this point that I do not want to give the impression that this could also be the root cause of the RA jumps in all the other cases) I could recognize kind of a knocking noise, especially amplified due to the relatively large C11 tube, with an interval somewhere around 5-30s. It was not present in every session, but as soon as it started to occur it did not go away and at the same time I could see the large RA spikes/jumps in PHD2. I did alot to rule out things and in my case it has nothing to do with power supply, USB, guiding or associated settings, belt tension or belt slip. Btw: I'm directly connected to the mount with a notebook via USB and I do not use ASIAIR.

Long story short - I decided to remove the front and counter weight covers, run my setup, provoke the knocking sound and have a look what exactly is happening inside the mount. With "run my setup" I mean: Mount supplied with separate 12V/5A power supply, direct connection to my computer via USB cable and sideral tracking started in the ASIMount ASCOM window (knocking noise is not present when tracking is set to off). What shall I say. It looks like the RA motor is snapping back in a regular interval. There is definitely no belt slipping. And as there is no other piece of software interfering, the issue must have its root cause definitely in the AM5N mount itself.

I recorded a video of this (hopefully this link works): https://drive.google.com/file/d/1BzbL5wN4N1btif_eidnZ-RBd0Ae4y37B/view?usp=drive_link

I already wrote a ZWO support ticket and attached the video in it. No response until now.

Furthermore I recognized that the issue does not appear when my setup is on the west side of the pier (but probably also just a matter of time). So my assumption is here, that the RA motor does not seem to have a problem if the weight/payload drives it in direction of rotation, but it snaps back the other way around. Not sure what this means at this stage, but my gut feeling tells me that this might be a hardware issue (insufficient RA motor power, RA motor electronics/mechanics failure) or simply poor motor driver firmware. "Hopefully" the last case and ZWO can come up with a firmware update.

Andreas

ASIMount-ZWO

F5146666
I'm sorry for the negative experience you had. Please check data 20cm and 25cm. The bigger the data is,the lower the load capacity is.

wc60Ld8X

Same here, got mine AM5n in december 2024 and it worked fine till last week.
Tried different settings on different nights and even Agr 100%, nothing helped.
Its is a SQA55 with ASI2600 Air.

I've also made a short screenrecording of the ASIAir App, the mount does not move as fast in one direction as in the others.
Video

CS, Adam

F5146666

ASIMount-ZWO

Interesting. You are advertising the AM5N with the following information:

Let's calculate the torque for the specified C11 setup that is shown in this picture in detail (downloaded from the ZWO homepage today):

C11 Tube: 11.28kg
Finderscope: 0.50kg
ASIAIR+: 0.22kg
ASI585MC: 0.13kg
Cables: 0.15kg

Considering the total weight of 12.28kg and a lever arm of about 28cm (from the RA-axis to the center of gravity of the C11) the calculated torque without using a counter weight is:
12.28 * 9.81 * 0.28 = 33.73Nm (this exceeds the stated maximum output torque by 12%)

Nonetheless, I already found the root cause of my RA spikes/issues. I disassembled my mount even further and found out that the breakaway torque of the RA harmonic drive is higher compared to the DEC harmonic drive. The DEC harmonic drive also runs smoother and is clearly easier to move. For me this was only recognizable when removing both motors and belts.
So I decided to interchange both harmonic drives and afterwards my RA issues were immediately gone. Now I partially have issues in DEC (what I was expecting somehow).

Please respond how to proceed. I need a replacement harmonic drive for the DEC-axis and as you can read - I am capable to change it myself. You can also respond to my support inquiry/ticket (that is still unanswered).

BR Andreas

ASIMount-ZWO

F5146666 I have forwarded your experience to the R&D team, and they are working hard to analyze the issue. I will let you know the results as soon as possible. Also, the ticket issue you mentioned is not handled by my department. I apologize for the lack of a timely response.