[Renato1 (Renato)]

Hi Everyone,
I've been trying to measure the highest useful magnification in my old 80mm ED f/6.25 refractor. The other night - cold, clear, no stars twinkling - I thought I'd figured out the bounds. With a 3mm eyepiece at 167X I had a very good image of Jupiter, but with a 2.5mm eyepiece at 200X - I had to stare hard to just make out the bands, though occasionally I'd see some faint detail. Not much contrast at 200X.

Then next night, I dug out my old University Optics achromat refractor and repeated the exercise. Again, good image at 167X, but a far worse image than in the ED telescope at 200X - I could barely make out a hint of detail

And thus I thought,
"Mission Accomplished - at 200 times, the scope is useless".
At which point some cloud went in front of Jupiter, and the 200X image in my achromat was suddenly better than in my ED refractor, with bands easily visible.

Of course, it's been cloudy or raining ever since, and I haven't gone back with Barlows or Powermate and Polarising and ND filters to see just how high a useful power I can get from the 80mm diameter.

So, I'm very curious. How far, magnification-wise, have you pushed your 80mm refractor on Jupiter before deciding the exercise had become pointless?
Regards,
Renato