AM5 guiding issue, random RA instabilities: Page 4

AM5 guiding issue, random RA instabilities

A51O69EE

I'm deeply saddened to report that the same curse has afflicted my AM5n as well. The mount was purchased in February 2025. As of last month, my guiding was phenomenal, allowing 10-minute exposures with no problem. This night (Sep 19), somewhat regular spikes began to appear in the RA axis. The guiding is otherwise perfect, except for periodic huge deviations. The issue temporarily subsided when the mount meriflipped from the east to the west. Nevertheless, as the photographed object progressed to the lower portions of the sky, the spikes re-emerged. I updated the firmware, but the issue persists. Will try to swing the RA axis a few times in each direction at full speed and see what happens.. I'm really disappointed at the moment.

From Slovakia
Drahomír

A51O69EE

Update: I have rotated the RA axis 360 degrees several times in both directions at full speed. So far, the spikes in the RA axis have not emerged (guiding proceeds at 0.6 - 0.7 total RMS; PA was done down to 7" total error). However, I'm not counting on this as the final, reliable solution for the future.

KHj89YaN

A51O69EE

I would recommend sending in a RMA ticket for your mount to simply get it into the queue. Given that the rotation in RA as a temporary solution is just that, temporary, I would proceed with sending in a ticket so that the problem can be documented and counts can be updated.

kaelig

A51O69EE

Hello, I am sorry that you have this issue. The high speed rotation of the RA axis is perhaps the beginning of the solution.
Could you make several nights with guiding and say here if the spikes have completely disappear?
All the experimental results are important.

Thank you for your help

A51O69EE

KHj89YaN Sure, I have prepared an RMA ticket. However, I did not take any screenshots or photos, nor save the guide logs (due to sheer frustration at that time), so right now, I have no attachments to send with the RMA. On the other night (after I had rotated the RA axis several times), I was ready to document the issue, but the guiding was good/ok all night, as well as the next one (i.e., the RA deviations did not occur).

A51O69EE

kaelig Hello, I'll keep it in mind. So far, I have been able to shoot for two nights. Before each, I did the RA rotating procedure and guiding was ok. Do you think that I should stop rotating the RA axis before each session and see whether the issue resumes?

F5146666

A51O69EE

Another case where RA-rotation seem to have worked, which is somehow good.

Regarding log files -> are you using ASIAIR or PHD2 on a PC? At least in the case of PHD2, log files are recorded and stored automatically. I am not aware what ASIAIR is doing here, as I do not use one.

KHj89YaN

A51O69EE

At this point, I think simply submitting a RMA is good because it updates their number of problem mounts. ZWO will have to respond with a solution faster if they are seeing more mounts being reported with RA guiding issues.

F5146666

A51O69EE

I would recommend to stop doing that, to see if the RA-spikes are coming back probably due to deterioration of the harmonic drive. And if they do not come back, this probably also means something. Would be a valuable feedback.

I also did not repeat the RA-rotation procedure and accumulated about 20h of exposure without having RA-spikes for now (3 different nights). I am trying to collect as much time as I can, if weather conditions are suitable.

KHj89YaN

F5146666

If this holds, I wonder if all of this is tied to the lubricant used and how viscous it is. It could be that it simply thinning out too much during use due to temperature changes (both external weather and interior use).

YPaWt83D

Just wanted to drop a message here, I’ve had my AM5n about 6 months (UK), but I started having issues about a week or two ago with my RA tracking: it started with slight spikes, until eventually it was just bouncing up and down like a yo-yo, but then after meridian flip, it was fine again!

It bugged me as nothing could be explained: it wasn’t windy, but I weighed it down anyway. Nothing was loose, but I tightened it anyway. I went through lots of trial and error but nothing changed.

Seen this thread, so during the day I decided to try fully rotating my RA on the AM5n back and forth about 3 times, then about 8 hours later in the evening, I set up my kit, and everything was perfect again.

F5146666

YPaWt83D

Good to read that. Thank you for sharing this information!

Support@Seestar

Any update on your investigation?

Andreas

Support@Seestar

F5146666 We've reached a conclusion, but it might not be convenient to share publicly for now. However, it's not a major issue.
Please wait for the final results. Thank you for your understanding!

KHj89YaN

Another poster in Astrobin disassembled their RA motor shaft and found another area of concern: the dec brake caliper. As they stated: "I took the DC brake apart and made some interesting discoveries. The front cover or caliper has a rough finish and it is clearly dragging". The photo they showed clearly shows that the caliper (break cover) was machined poorly with ridging which will cause unwanted friction and poor performance. Based on all of these threads from all of the astronomy sites, it really looks like there was a lack of consistent quality control with the AM5N. From wave washer issues to a rough DC brake caliper, there was clearly quality leaks throughout the manufacturing process for this mount. @support@Seestar What are ZWO's newest findings? It has been two weeks since the last update.

KHj89YaN

Support@Seestar

Thank you for this update. I understand that there are legalities regarding public disclosure right now and it probably needs to have final vetting/approval, however; did ZWO come to the conclusion that it is indeed a hardware issue? Likewise, is ZWO looking to conduct preventative replacement of whatever components of the AM5Ns that are faulty as a blanket recall (like the automotive industry does when a fault is detected in a model regardless if the model has exhibited the fault)?

KHj89YaN

Support@Seestar

Awaiting your response for clarification from your statement and a time table for the final results. I have sent in another RMA with this statement as documentation that there is an acknowledged fault with the AM5N.

ahsiang-c

I had the same RA spiking problem for my AM5N purchased in August 2024. I recently went through the RMA process and got a replacement a couple of weeks ago. It looks like the unit is manufactured in May 2025. I ran a test last night. The RA spikes are gone. However, the guiding accuracy before meridian is much worse than after meridian. 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:

As 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.

I 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.

How do we explain the east/west asymmetry?

My latitude is 37N. I use NINA on a mini pc to control the rig. My scope is a Astro-Tech AT115EDT f/7 ED Triplet Refractor that weights 15.25 pounds.
Guide settings:
Pixel scale = 4.98 arc-sec/px, Binning = 1, Focal length = 120 mm
Search region = 15 px, Star mass tolerance = 50.0%, Multi-star mode, list size = 12
Camera = ZWO ASI290MM Mini, gain = 65, full size = 1936 x 1096, have dark, dark dur = 500, no defect map, pixel size = 2.9 um
Exposure = 500 ms
Mount = ASI Mount (ASCOM), connected, guiding enabled, xAngle = -45.5, xRate = 1.402, yAngle = -137.7, yRate = 1.494, parity = ?/?
Norm rates RA = 7.0”/s @ dec 0, Dec = 7.4”/s; ortho.err. = 2.2 deg

X guide algorithm = Hysteresis, Hysteresis = 0.100, Aggression = 0.700, Minimum move = 0.120
Y guide algorithm = Resist Switch, Minimum move = 0.120 Aggression = 90% FastSwitch = enabled
Backlash comp = disabled, pulse = 314 ms
Max RA duration = 200, Max DEC duration = 200, DEC guide mode = Auto

Support@Seestar

KHj89YaN
OK, our technical support colleagues will take care of it.

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