refractors are the bomb@some questions?

why can't any manufacturers out there produce a good 7" tube achro. for about 1500.00. also why can't they produce ca corrector auxillary lens for the cheap chinese refractors, like was done for hubbles spero aberation?

thomas zukouski said:

why can't any manufacturers out there produce a good 7" tube achro. for about 1500.00. also why can't they produce ca corrector auxillary lens for the cheap chinese refractors, like was done for hubbles spero aberation?

Valery Deryuzhin produced the Chromacorr for a while, I hear rumors he may be making custom Chromacorrs. I think that is what you are looking for.

Jon

I wonder sometimes if the difference between "considerably better" and "perfect" doesn't get between our standards and our pocketbooks. The price break between BK7 and CaF2 blanks is so considerable that many can't put an ED in their back yard. Valery's ChromaCorr produces legend-making results when paired with the specific scopes they were designed for, but how many of us can afford both the scope and the ChromaCorr? There must exist a price point that links what most of us can afford with what a manufacturer can profitably make in quantities that fill a known market. Economic feasibility from a manufacturer's point of view does not often enter into our discussions, yet it is the decisive factor that will or will not put products into our hands. I'd like to hear what Rolando and other designers say about the cost-practicality of putting a doublet or triplet that brings the violet within range of the red-green, and will screw into a 2-inch eyepiece like a filter. For one, will any design be up to the task that far down the wavefront and that close to the image plane?