Quote:
Originally Posted by mental4astro
Marc, you make SCT's sound like poison  ! 
SCT's are fine visual instruments. |
Hi Alex,
I would say they are "reasonable" visual instruments. Pure physics determines that a SCT cannot equal the optical "visual" performance of an equivalent aperture newtonian, or refactor. Nor can a MCT for that matter, although a high quality MCT like a Questar, Quantum, Astrophysics or Intes and Intes Micro will put up a very good show.The 7" Meade MCT is an excellent scope, but it won't outdo a good 7" newt or refractor. Keep in mind also that these Maks are premium scopes and not typical of the mass produced SCT's. In 40 years of searching for the ultimate SCT that can prove the physics wrong, I am yet to find one, despite a heck of a lot of trying. That doesn't mean that some with good optics can't give nice views, they can't match the performance of an equal aperture newt or refractor, although the good ones with decent optics and properly cooled can put up a 1/2 decent fight. Unfortunately a lot of SCT's have marginal optics. Rod Berry (Rodstar) sold his rather expensive 10" Meade LX200 after 2 years of frustration. Every time we observed together, which was quite often back then, Rod would be continually dissappointed with the high power views in his scope compared to my 10" newt. I felt the performance of Rod's scope was typical of the performance of a lot of other SCT's I had looked through over the years from both Meade and Celestron, ranging in aperture from 5" to 16". Rod subsequently sold the SCT and bought the Mary Rose (20"/f5 SDM) and hasn't regretted his decision one bit. The performance of Rod's scope was partly due to mediocre optics and partly due to the cooling issues of a closed tube design. My 10"/f5 GSO newt, which has a great mirror in it for an $800 scope will pull 500x on night of good seeing. My 10"/f5.3 SDM with Suchting primary will pull 675x (5mm Pentax XW + 2.5x TV Powermate) on a night of good seeing. How many mass produced SCT's can do that?
That's not to say SCT's don't have their place. They make an excellent all rounder if you plan to do both visual and imaging with the one telescope and they offer a portable, transportable package. The quality of lunar planetary images Damian Peach takes with 11" and 14" SCT's is testament to that. However, if you want ultimate visual performance from a telescope then a SCT is not the best choice IMO.
Richard has indicated he is only interested in visual astronomy. If storage and transport are not a concern then a 10" GOTO dob ($1,499) is a way better choice than an 8" SCT IMO. He can buy one of these new for what an 8" SCT will cost him 2nd hand if he's lucky; and will see a whole lot more tnan the 8" SCT can show him.
http://www.bintel.com.au/Telescopes/...oductview.aspx
If transport and storage are issues then a 10" collapsible tube dob may be a better option.
http://www.ozscopes.com.au/skywatche...telescope.html
If Richard wants to try imaging at a later time he could start with a small refractor for imaging and keep the newtonian for visual.
Cheers
John B