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Old 25-10-2006, 09:01 PM
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[1ponders] (Paul)
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Join Date: Nov 2004
Location: Obi Obi, Qld
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Putting a mask on a refractor won't act as a barlow, it will just slow the focal ration, the focal length will remain the same. To increase the focal length you need to "add length" by using lenses. Stopping down the aperture the way you are describing will reduce resolution, which is dependent on aperture size.
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