Hi everyone,

It seems like yet another AM5N mount is experiencing issues with the Right Ascension (RA) axis. I purchased the mount as soon as the first units arrived in Spain, and everything was working fine until I started losing subs night after night.

Over the past two nights, I’ve lost a total of 63 subs — all due to RA errors. The same correction wave that others have reported above is clearly visible. I’m attaching several screenshots from last night to illustrate the issue.

I’ve spent the last two nights testing various settings, but nothing has worked. For the next session, I’ll try removing the counterweight and running a full night, although I doubt it will make a difference. In fact, after reviewing the recommendations at the time of purchase — and based on the balance readings I was getting — I found it necessary to add a counterweight. I also tried raising it along the bar, with no improvement.

Sessions start fine, but after about an hour or an hour and a half, the error begins to show up. It repeats consistently at irregular intervals of 5, 8, or 10 minutes. The more circumpolar the target, the less severe the issue seems to be. For example, with NGC 6939 and 600-second exposures, I lost 9 subs total over the last two nights. That contrasts with the 900-second subs I was getting when I first bought the mount, imaging the Ghost of Cassiopeia — I didn’t lose a single frame, and the configuration was exactly the same.

On the other hand, targets like M92 or NGC 6229 — closer to the eastern side of the meridian — show a significantly higher number of errors.

I have a second rig with an iOptron mount shooting the same targets, and its guiding is much more stable, with losses only due to passing clouds (if any).

I’m attaching the screenshots and full setup details — all equipment was purchased in October last year. Everything is from ZWO except for the filters:

Telescope: ZWO FF107 APO

Camera: ZWO ASI2600MM Pro

Mount: ZWO AM5N

Filters: Antlia V-Pro LRGB

Accessories: ZWO ASIAIR Plus • ZWO EAF • ZWO EFW 7 x 36mm • ZWO OAG-L

Guide Camera: ZWO ASI220MM Mini

I’ve tried adjusting pulse duration, correction aggressiveness, and guiding speed — nothing has worked. I would really appreciate some support to help resolve this issue, if possible, without having to send the mount in for repair.

I posted my problem in a thread that seems to be abandoned by support since it hasn't received any responses from ZWO, that's why I'm starting this new one.
https://bbs.zwoastro.com/d/22171-problem-with-am5n/25