Quote:
Originally Posted by Larryp
Agreed John
I once had a 6" AP Starfire, and remember lining it up against a friend's C11 one night-there was nothing visible in the C11 that could not also be seen in the Starfire-its all about CONTRAST! Of course we are talking about the ultimate in refractors.  |
Larry you have picked the best of the best in terms of 6" refractors and compared it against one of the worst 11" telescope designs going; in terms of visual performance. As I said in another thread, SCT's make poor visual instruments for several reasons. Very large central obstruction (33% plus), the thermal cooling issues caused by the closed tube design and the corrector plate; and the additional air to glass surfaces over a newtonian, namely the star diagonal, the corrector plate and in many cases a focal reducer. On top of that these are mass produced telescopes with fast F2 to F2.5 primary mirrors and the optical quality of a great many of them is downright poor.
Try comparing your 6" AP refractor to my 10" SDM (Suchting mirror) or my 14" SDM (Zambuto mirror) on a night of decent seeing and see how they it fares.
I have had my 18" Obsession to 1075X on the Moon and Saturn and my 14" SDM to 800X on the same two targets. The 14" Zambuto would go higher under ideal conditions, but I dont have the eyepiece/barlow combinations to go any higher, without stacking barlows. Try 800X plus with a 4" or 6" refractor and see how nice the image holds up.
Honestly, to think that a 4" refractor is the best choice as a visual telescope for someone who is only going to have one telescope, considering that 90% of what we observe usually are DSO's which benefit from greater aperture, is 1970's thinking at best, or the thinking of someone who needs to sell a Takahashi refractor IMO. Unless of course there are other reasons aside from visual optical performance which need to be considered.
Cheers,
John B