Re: How to distinguish 160 vs 170 mm eypieces?

Kevin Cunningham writes:

I wrote one of the books you use.

Let's see, Smith, Smith, Smith, Longhurst, Born, Wolfe, Kingslake, Twyman,
Driscoll, Vaughan, Jacobs, Chang, Murphy, Crisp, Zeiss, OSA, .... Which
one is yours again?

Eyepieces made by any one other than the manufacturer don't work.

Other than the minority of compensating designs, this is simply not true.
.