![]() #High powered telescope freeThe best refractors, free of chromatic aberration or optical defects and made for both imaging and visual astronomy, have eye-popping prices – often several thousand dollars for something just 3” or 4” in aperture. Inexpensive refractors are almost always achromats which require long focal ratios and consequently long tubes and narrow fields of view to minimize chromatic aberration – the ugly purplish halo around bright targets caused by the inability of the objective lens to focus all colors to the same point.Īpochromatic refractors are heavier and more costly, with many often still suffering from some chromatic aberration – particularly those made for imaging. The cynical would say that the definition of an astronomer is someone willing to spend a fortune to make a little ring of purple go away – and they’d be right.
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