|
This is certainly surprising with a refractor. I'd expect that with an SCT. Having said that the in and out of focus airy pattern will always look sharper on the out as the air turbulence inside the tube will blur the disc.
When testing with a barlow you usually introduce aberrations that are not from the original telescope unless you have a very hig quality barlow like a Baader FFC.
The colour shift in your photos is obvious and I think it's your barlow.
|