Assertion: eyepiece's quality | /r/HasProperty | the form of the könig eyepiece
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text: 60 degrees: a typical field of view provided by an Erfle eyepiece; this type of eyepiece was the type of eyepiece used by amateur astronomers looking for a very wide field of view in the 1960s and previously, as noted above, there were five and six element designs called by this name, and it involved some compromises of optical quality; other eyepieces with this same field of view, and higher optical quality, include the form of the König eyepiece currently available, and the Radian eyepiece by TeleVue;