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Message: <blockquote data-quote="John Russell" data-source="post: 2917432" data-attributes="member: 22179">The dew shields of the ED80s might have as much as 100 mm diameter, so the optical axes of the Porro prism erectors would need to be around 20 mm offset for you to attain a usable IPD of 60 mm or greater.However, although Televue and others used to sell them, they don't seem to be available any more, apart from the Kowa Porro prism adapter for their telephoto lens, and that is very expensive. By the time you've bought the two ED80s, Porro erectors, bino platform and eyepieces, it might be almost as costly as a Docter Aspectem!John</blockquote>