Interesting article.

Not really being a 'fractor guy, this is new-ish territory for me. Coupla questions:

1. So Clive, you're saying that a lot of the more affordable ED refractors have intentionally shifted the CA toward the red, which in your opinion is not such a good thing....and that a prism diagonal can help shift the CA back to the "normal" range. Is that more or less correct?

2. "Another optical characteristic of a diagonal prism is that it's naturally overcorrected for spherical aberration." I don't understand this. Please explain in a bit more detail. Thanks!

Clear skies,

Jim