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Lawrence Sayre
Abbe Normal
Reged: 10/16/04
Posts: 4736
Loc: N.E. Ohio
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As stated before, it took nearly 100 years before anyone equated the negative field flattener in a telescope eyepiece with Smyth. People like to make associations. Does this make all such associations correct? If so, then I state that Petzval likewise invented the idea (not really).
Per the testimony of someone here who asked him this directly, Al Nagler scoffed at the idea that his negative field group was a "Smyth". With this being the case, does it matter what Rooten and vanRooij thought it was in reference to Al's design?
Rooten and vanRooij likewise equate the Barlow directly with eyepiece field flattening. See page 155. Why do you scoff at the idea that a Barlow can be used in relation to eyepiece field flattening when your very source clearly states that it does?
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My philosophy, in essence, is the concept of man as a moral being, with his own happiness as the moral purpose of his life, with productive achievement as his noblest activity, and reason as his only absolute.
Ayn Rand (in the appendix to 'Atlas Shrugged')
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David Knisely
Postmaster
Reged: 04/19/04
Posts: 8270
Loc: Beatrice, Nebraska
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Lawrence Sayre wrote:
Quote:
Rooten and vanRooij likewise equate the Barlow directly with eyepiece field flattening. See page 155. Why do you scoff at the idea that a Barlow can be used in relation to eyepiece field flattening when your very source clearly states that it does?
I don't scoff at the idea. A Barlow can produce some flattening of the field, but the idea again is intent. The Barlow may not be able to completely compensate for a severely curved field. This is where *deliberately* designing a field flattener out in front comes in, as it is set up to *match* the field curvature of the positive lens set of the eyepiece, thereby canceling it out. It isn't a "built-in" Barlow used so that cheap eyepiece designs might be used at shorter f/ratios; its intent is for field flattening from the word "go". Clear skies to you.
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David W. Knisely
Hyde Memorial Observatory
http://www.hydeobservatory.info
Prairie Astronomy Club
http://www.prairieastronomyclub.org
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