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    Re: NG's "Midnight Fun"
    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 Fogg  wrote:
    >
    >
    > 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.
    >
    >
    
    
    
    

       
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