Thread: Is there such a thing as photography Barlow?
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Old 19-06-2017, 05:50 PM
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Merlin66 (Ken)
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Join Date: Oct 2005
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the rule of thumb is focal ratio "optimum"= x5 the pixel size.
This generally means ratios around f25 to f30.
If you have a f5 scope, then x5 is pretty close.
If you can find a TMB x1.8 barlow, you'll be impressed.
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