More On Barlows - an Astronomy Net Eyepieces Forum Message

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More On Barlows

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Posted by Jarvis Krumbein on November 15, 2001 05:00:17 UTC

Hi Robert,

Needless to say, I disagree with Bob's assesment of Barlow lenses and eyepieces. First, a really well designed Barlow will not degrade the image. The Barlow will show a great improvement in image quality when used with the typical F4.5 Dob. Most modern eyepieces do not perform well with fast systems and adding a Barlow will almost always result in a marked improvement in the image. I realize that you are using an F10 system so this is not nearly as important but the better eye relief, compared to the relief with shorter focal length eyepieces, is a factor to consider. Dollars are also a major consideration. A really good Barlow and a reasonably selected assortment of top quality Plossel eyepieces will cost about a third of the expensive alternative. I've used the eyepieces that Bob recomends and I agree that they are truly excellent, but I rarely find that their full capabilities are required. By the way, I'm using an 13.1" F4.5 Newtonian on an equatorial platform although I have a 20" compound (modified Gregorian) under construction. The mirror in this beast is an F3 thin slumped (1" thick) pyrex blank that was originally used as a tool while working on a 32" Hextek mirror.

Jarvis Krumbein, jkoptic@juno.com

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20" Gregorian - robertko2 - November 15, 2001 - 20:56 UTC

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