BTW Frank,

If you wanted to, you could put your handset into "PC Direct" mode (it's in the utility menu) and use the EQMod INDI driver instead of the SynScan driver. That will work with the same cable, no new cable required. The EQmod people don't recommend that for long term use, only short term testing. They recommend a proper cable that plugs directly into the mount (not handset) for long term use.

This is the result of my test:
I tried to use both the SynScan driver and the EqMount driver, as suggested by Kross.

In the first case (SynScan) some problems occur. The problem should be in the A.R. coordinate. Every time I start to synchronize an object starting from the position of the celestial pole (more or less) the Dec coordinate seems approximately the same, whist this is not the case of the A.R coordinate.
If I synchronize an object once I've already synchronized a previous one, then the error propagates and the position showed by the SynScan marker results completely wrong.
On the other hand, if I run the session using the EqMount driver, the manual synchronization works very well and the marker points at the correct position every time I synchronize an object with the mount.

In order to have a direct view of this test I acquired a video. Apologizes if I am not enough clear.
Thank you again for your efforts!

Here the movie...

I'm glad you found a working solution!

Other than my specific problem, I think that Kstars is a considerably useful and complete software for astrophotography and also for professional astronomy. It really worths to have also this problem fixed in future

Agreed! It's a complete all-in-one solution, that even works in a distributed environment over the network. I have a Raspberry Pi on my scope talking directly to the hardware, while I'm in the house with KStars/Ekos/Stellarium connected to INDI on the Pi over the network. Very nice!

Being free software (free as in freedom, open source) is what attracted me to it in the first place. That it's so feature rich is what keeps me!

I've been corresponding with Skywatcher support, and they said we should only be sending the sync command to the mount, and not the reset position command. We're supposed to have clear skies tonight, so I will make the change locally, and try it out tonight. If it works well, I'll get that checked in.

So did some testing. Things are improved, for sure, but not perfect. Plate solving and syncing actually works, mostly! The "solve and slew to target" option to re-center a target on screen sorta works. It solves and syncs properly, then slews to the new location properly. But then it takes another image while the mount is still slewing, causing a blurry captured image, which of course fails the plate solve. But it actually got us close enough on the first try I don't mind.

Polar alignment assistant still doesn't work with Synscan driver. The mount has a tendency to go crazy.

But this is a definite improvement. I put in a pull request with the change.

So ...it sounds as a greeeeeat new!!!
This improvement is a considerable step forward to solve this problem.
Actually, I prefer to use the synscan driver to use kstars ekos around. For this reason I am very interested in your work and I prefer to wait for a new release in which this issue has been fixed.
Thank you for your efforts!!!

Yeah, this Is great news! I'm really interested in the synscan driver too, so I can go to the scope and still get my hand controller features. Its very useful in the field. Thanks!

The changes have been committed. They should make it into the next nightly build of INDI. If you're using a Raspberry Pi with Raspbian (not Ubuntu Mate) for your INDI server, there are no nightly builds, you would have to build from source.

Polar alignment assistant still doesn't work properly, but regular star alignment with plate solving does work, as long as you're not too far off in your initial pointing (less than 5 degrees). If you do a very rough 1 star alignment from the handset first, then all the subsequent plate solves and syncs should work.

Thank you again Kross!
I have only two questions that are dictated by the fact that I'm relatively new in the forum and a primer in the use of Kstars.
Does the Mac OS release with your improvements will be distributed in the form of a new Kstars installer? Does the new release will be published in the newsletter or is it already available?

Last I checked, the Mac OS version does not support DSLR's due to USB interface issues so if you have a DSLR in your system, you'll need to drive it with a linux computer. I think many - if not most - use a Raspberry Pi. So these driver updates would be readily available for that. Presently I use a Mac remotely connected to an RPi3(B+) which runs all the drivers. I highly recommend this setup and buying a StellarMate to get a ready built system.