Dear ZWO Technical Support,
I am writing to report a persistent and verifiable issue with the AM5N mount when used in conjunction with ASCOM and control software such as N.I.N.A. and Stellarium. The problem relates specifically to the inability of the mount to maintain accurate sky positioning after synchronization, which severely affects pointing precision during imaging sessions.
Issue Summary:
The AM5N mount consistently exhibits a pointing offset of up to 1 degree between its reported coordinates and the actual position of the telescope on the sky.
Even after performing a precise plate solve with N.I.N.A. and executing a synchronization command via Stellarium, the mount does not retain this correction when moving to other targets.
This causes significant framing errors and renders mosaics or precise target framing impractical, especially with long focal length telescopes.
Testing Performed:
I have centered objects such as M81 or Polaris with arcsecond-level precision using plate solving.
After issuing a Sync command via Stellarium, the telescope appears to be aligned locally, but when slewing to another object (even nearby), a pointing error of ~1° reappears.
The error persists whether syncing from Polaris, M81, or any other region.
I have confirmed that this is not an issue with Stellarium or N.I.N.A., as the same behavior occurs using other planetarium software and plate solving methods.
Moreover, I have observed that the driver rejects synchronization commands near the polar region, returning an error ("Cannot synchronize within 5° of the polar circle").
Community Confirmation:
I am not the only user experiencing this issue. Similar reports can be found in public forums, such as Cloudy Nights:
https://www.cloudynights.com/topic/942262-am5n-and-nina-3ppa-not-liking-each-other/
Request:
Given the above, I respectfully request:
That ZWO review the AM5N ASCOM driver’s handling of synchronization commands and pointing model persistence.
That a future driver update addresses:
Reliable SyncToCoordinates() support via ASCOM.
Elimination or configurable override of the 5° restriction near the celestial poles.
Improved pointing accuracy across the entire sky once a sync has been performed.
Please let me know if logs or additional technical information are needed to assist your investigation. I would be glad to provide further data or replicate the issue in a controlled scenario.
Thank you in advance for your attention and support.
Sincerely,
Leonardo Ruiz
