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  1. #1
    jdvann's Avatar
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    Default Barlow vs Tele-extender



    What is the difference between a Barlow and a tele-extender? Are they the same thing?
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    Default

    Sort of. A barlow doubles or triples the magnification of an eyepiece whereas a tele extender is used in combination with eyepiece for eyepiece projection photography which extends the focal length of the scope.
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  4. #3
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    Default

    Is a tele-extender then not for visual use?
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  5. #4
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    Default

    I believe they're both suitable for visual use, but a tele-extender (presumably you're referring to Televue's Powermate and/or other vendors' "telecentric" barlows) incorporates some form of optical correction over that of a normal barlow lens. Unfortunately I am not sure of what aberration it's correcting for -- astigmatism? coma? spherical aberration? field curvature?

    Depending on the type of aberration it's correcting, it may or may not be noticeable compared to a traditional achromatic/ED barlow.

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