ATM - Best Secondary Size

[Richard Schwartz <richas@idt.net>]

Dwight, thanks for your very correct answer to George on diagonal
size.   There is way too much orthodoxy, and way too little thought give
to this.  One size does NOT fit all.

One nit to pic....  it is the distance from the diagonal center to the
FOCAL PLANE that matters, not the end of the focuser.   If there is a
camera body, the focal plane can be way outside the end of the focuser.

. . . Richard