Re: ATM Barlow Lens

[Richard Schwartz <richas@idt.net>]

rutherfordt@ten-nash.ten.k12.tn.us wrote:
> 
>      A question or two.  What is the difference between a standard barlow
> lens and a "shorty" barlow lens (except for the obvious difference in
> length)?  

A shorty is to a standard barlow as a cassagrain is to a newtonian. 
Lenses of stronger (and opposing) curvatures are used to allow a long
focal length in a tube of shorter physical length (like a cassagrain).

I have no specific information, but I surmise that stronger curves
generally come with stronger aberrations.