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Long focal length Achromat refractors were The primary scope solution for many decades because the technology had not evolved to where other options were available in the retail environment. As has been pointed out, the f ratio is not really significant for visual use, and a f12 to f15 achromat refractor can give you wonderful visual performance with almost no visual CA. True colour rendition is a major advantage of reflector, which do not need expensive exotic glass formulations. Not surprisingly the science community migrated to reflector designs early, as they are the most cost effective apeture you can buy, and can be built in large sizes required for exploration. I believe the change has taken place relatively quickly.
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