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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: NG's "Midnight Fun"
From: Hewitt Schlereth
Date: 2010 Jun 14, 20:09 -0400
From: Hewitt Schlereth
Date: 2010 Jun 14, 20:09 -0400
Peter - A "furphy"? I like the sound of it; but what is it? Hewitt On 6/14/10, Peter Foggwrote: > > > George Huxtable wrote: > > > > As that posting confused distortion with perspective, it had little > > relevance to the matter in hand. > > > > No. George is wrong. I have been careful, unlike George himself, even in > his latest post, to distinguish apparent distortion, such as the effects of > perspective, from other distortions caused, by example, by the shortcomings > of lenses. > > > > > This question takes on a bit of importance because postings appear on this > > list, quite often, from proponents of the use of cameras for making > > celestial measurements. The geometrical distortions discussed here, that > > arise from portraying a spherical surface on to a plane array, add serious > > complications to interpreting measurements, and deriving scale factors; > > complications which are often neglected. > > > > As in a lot of stuff you post, George, you confuse the theoretical with the > practical. The examples of "use of cameras for making celestial > measurements" that's I've seen here involve the sun's image near the centre > of the image field. In this case there is nothing, in any practical sense, > to worry about in respect of what may happen to other parts of the image > towards the edges of the field, from whatever cause. Once again, like so > many of these you trumpet so loudly so often as matters of grave concern, > its just a furphy. > >