The objective diameter of my scope is 57.0 mm, should I use Flip-Open 56.4 (#39 ) or 57.2 mm ( #40 )?
Same scenario for the eyepiece which is 43.1 mm, should I use Flip-Open 42.5 ( #17) or 43.2 mm (#18 )?
Thanks in advance.
Same scenario for the eyepiece which is 43.1 mm, should I use Flip-Open 42.5 ( #17) or 43.2 mm (#18 )?
Thanks in advance.