Wasn't there a ratio between the objective lense, zoom and exit pupil? Zoom times exit pupil equals required lense diameter to get the nest out of it? So with the Deltas I see the 10x42 have an exit pupil of 4.2 (10x4.2=42) and the 10x50s have an exit pupil of 5mm (10x5=50). Looking around that seems to be common sizing.
I need to stop looking around and pick some, this is starting to do my head in lol
Oh bloody hell now I've seen the athlon range...
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