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I'm still puzzled as to what scopes Vixen intend these to be used with.
Such short focal lengths only make any sense in fast reflectors (f/4 and under). But... very fast reflectors usually have relatively poor surface figure and whopping secondary mirror obstructions, which mean they are poor performers at high power.
Even at f/5, the 2.4mm will give X2 per mm, which is too high for most reflectors, and no-one makes f/4 APO refractors.
And does anyone really need X3 per mm ? I doubt it...
A 3.4mm is at least sensible as it would suit f/7 APO refractors that can usefully handle X2 per mm.
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