Past about 55 degrees,
no eyepiece can be said to be orthoscopic.
Nothing against any type, it's just that
a lot of geometric distortion is needed
to keep focus. It's a mapping thing.
Abbes, Symmetric Plossls, RKEs, and 1,2-Konigs
are very "orthoscopic", if they stay near or under 50-degrees.
For reading linearly-marked meters like dosimeters, pressure gauges,
golf-distance monoculars, or measurement/inspection loupes,
the 1,2-Konig is most commonly fitted with a reticle.
A 1,1 symmetric Ramsden is sometimes used, but with a color filter.
Edited by MartinPond, 03 March 2021 - 08:50 AM.