Assertion: eyepiece's eye lens | /r/HasProperty | replaced with achromatic doublet
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Source sentences:
text: The Kellner eyepiece (see Fig. 3.35) is essentially similar in action to the Ramsden eyepiece, with the eye lens replaced with an achromatic doublet, and has much improved corrections for the aberrations, though its eye relief is not as good as that of the Ramsden eyepiece.