There is a little bit of color shift but the filter looks like a good addition to an achromatic refractor. [adjective]
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If you are using an achromatic refractor, the focus errors will be larger due to chromatic aberration of the telescope. [verb]
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This wonderful lens is achromatic, and free from spherical aberration and distortion of image. [Please select]
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Achromatic: free from color; tissue that does not stain readily. [Please select]
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When viewed by the aid of a powerful achromatic microscope, the central part of the fibre has a singularly glittering appearance. [Please select]
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If you hold a common reading-glass some distance away from large print you will see that the letters are edged with coloured bands, proving that the lens is not achromatic. [verb]
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