The difference is a lot of what has been already mentioned but I will add my own small wrinkle in the dollars spent to value received discussion.
I have a Sky-Watcher 4 inch F/9 apo that is truly superb, tested at 360× and I could not detect ANY aberrations.
No CA and no SA.
A snap-to focus that is dramatic.
SW is, of course, not marketed as a boutique instrument just a very well executed design with many years of production behind it.
Is it that factor that has transformed them, more likely than not, from being good to being great?
Even if it was just an average sample, a good scope, it would still be a marvelous transportation machine able to take one on many wonderful and great journies to happyland.
A great one does exactly the same journey but the trip is more like taking a first class ticket ride to perfect contrast and amazing sharpness where one runs out of light before image breakdown occurs.
After two years of use it has become crystal clear that it is truly superb and not merely great!
The cost savings maybe assumes a less rigourous quality standard than more upscale brands but I believe its long production history equalizes that margin considerably.
Clear skies & Good seeing
P.s. I enjoyed spending the savings on some great eyepieces instead.
P.p.s. totally agree that a superb instrument is a VERY ADDICTIVE drug, my drug of choice!
Edited by PKDfan, 25 September 2021 - 12:05 AM.