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Thread: Using Barlow on refractor telescope

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    Default Using Barlow on refractor telescope



    Should I put the Barlow before the star diagonal on my refractor telescope

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    Default Re: Using Barlow on refractor telescope

    No, the diagonal goes into the focuser tube of the scope, the Barlow goes into the diagonal, and the EP goes into the Barlow.

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    Default Re: Using Barlow on refractor telescope

    HI! I have always used my Barlows on the back of the diagonal and slipped the eyepiece into the Barlow. I am pretty sure this is how they are intended to function. But now you have me curious! Lol!

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    Default Re: Using Barlow on refractor telescope

    If you put Barlow first then diagonal you get more power as the cone of light has more distance to expand. Never measured it but it is about one more power. A 2x Barlow would be a 3x this way.
    Newtman but some refractors allowed.

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    Default Re: Using Barlow on refractor telescope

    Quote Originally Posted by tomjones View Post
    If you put Barlow first then diagonal you get more power as the cone of light has more distance to expand. Never measured it but it is about one more power. A 2x Barlow would be a 3x this way.
    The standard way to use a Barlow is indeed scope-optional diagonal-Barlow-eyepiece and only in this arrangement is the magnifying power as specified. The magnifying power of the Barlow depends on the distance from the Barlow lens to the eyepiece. Greater than the designed distance and you get greater magnification.

    So if you get 3x by placing a 2x Barlow in front of the diagonal depends on the optical path length of the diagonal. 2" diagonals have a longer optical path generally than 1.25" diagonals. Different manufacturers have different designs. So if you need to be sure, you have to check. This is easily done daytime looking at a distant ruler. No need to waste a clear dark night.

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