Now, for my two cents worth...
There's nothing magic about an SCT. Like all scopes (of any design), there are good examples and poor examples. I have seen very nice SCT's (I'm perfectly happy with both of mine), and I've seen poor examples. I've seen very nice Newtonians that will give my SCT's a run for their money, and I've seen others that make me wonder why the owners even bother. Refractors are not immune, either. Even some of the ED's and (semi?)APO's that I've seen are not that great. As I've said before, most of the time I'm left wondering if the owners of many of these bad examples truly understand the process of collimation or if those scopes really are that bad? I suspect a little of both. Then there is the question of eyepiece quality, along with a plethora of other variables that add in to the equation. The list goes on and on.
I think what Dave is trying to accomplish here is to show that given enough attention to detail, even some of the worst offenders can be made into silk purses. By his own admission, it's not something that the original manufacturer could afford to do given the tools that they had to work with. They probably would have been wise to stick with what they were very good at producing, but in a competitive marketplace, stagnation usually amounts to failure in the end. Then again, even with the success of the major American product lines through the years, the glut of cheaper imports eventually took its toll.
Dave is a teacher, and a good one at that. I'm following this thread with great interest, and believe me, I am learning from it. My only fear is that people who really don't understand the process of collimation will begin to perform AC tests on their scopes and misinterpret their results. I have to say that I understand the process and the reasoning behind this testing method, but I really don't understand the math behind the choice of lighting, Ronchi screen and the process of actually interpreting the results. Then again, if you do enough internet searching, there's a tremendous amount of disagreement among the experts on this subject as well (there always is). Since Dave is leading this thread, I intend to listen to him and learn.
I still have a fear that instead of making a few minor tweaks to improve performance on a scope to an acceptable level (whatever that is), the owners of these older scopes might start polishing away merrily on their mirrors, lenses and corrector plates and make a real mess of things. Then one day, we will be buying used scopes with all sorts of problems. Then again, I also realize that there are a lot of very competent people out there that will be able to follow Dave's lead and end up with the scope of their dreams. I guess it's a bit of a double-edged sword.
Oh well, maybe I'm just paranoid.
Bill
I hope it's true. I just don't trust magic optics.
