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    batheyedoc's Avatar
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    Default Getting my head around lenses.....



    Esteemed forum members,

    Apologies is this a repeat, but could someone give me a brief explanation of what a focal reducer is, and why one would need one?

    Very many thanks!

    Jon

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    KathyNS's Avatar
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    A focal reducer is a lens that reduces the effective focal length of a scope. You would use one to increase the field of view by decreasing the magnification. You would also use it to increase the amount of light available for astrophotography by reducing the focal ratio.

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  4. #3
    batheyedoc's Avatar
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    Thank you Keith

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    A focal reducer is the contrapositive of a Barlow. The barlow takes a small FoV (say 0.625") and creates a larger FoV from it (say 1.25 = 2X Barlow). The field reducer takes a big FoV (say 2") and shrinks it down to a smaller size (say 1.25" = 0.63X reducer.)

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