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Buying a Refractor
Never had a refractor - thinking I probably should scratch that itch.
Looking at 125mm - 150mm achromats it seems that none has a long enough focal length to reduce chromatic abberation to an acceptable level or to reach the diffraction limit for the aperture (based on the various formulas floating around eg Sidgwick).
Is it feasible to stop down the aperture to meet the constraints the physics for lunar and planetary and open up for deep sky.
Thanks
Robert
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