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Thanks Dan,
This is one field that I poorly understand. I thought and still believe that the super short EP's (3mm say) were really pushing the envelope of sensible refraction and therefore good ones would be pricey; like low f-type apo refractors. Conversely, I thought that long EP's (say 20-40mm) did not bend the light as savagely and were therefore easier to make and therefore less pricey; like high f-type long achromats. You've corrected me and given me something to think about.
Thanks.
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