Hi Werner,
Very nice work you have done there.
I was looking at that same view of Saturn in my scope the other night and thought that it would make a great image, thanks for doing it and showing us.
The bright spot in the middle is Elysium Mons. Its diameter is about 240 km, with a summit caldera about 14 km across. Elysium Mons was discovered in 1972 in images returned by the Mariner 9 orbiter.
And here you can see, how the seeing was. Done with IR-pass filter.