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From: whisky-dave on 3 Jun 2010 05:49 "Wolfgang Weisselberg" <ozcvgtt02(a)sneakemail.com> wrote in message news:uraid7-2en.ln1(a)ID-52418.user.berlin.de... > DanP <dan.petre(a)gmail.com> wrote: >> On 2 June, 02:00, Wolfgang Weisselberg <ozcvgt...(a)sneakemail.com> >>> DanP <dan.pe...(a)gmail.com> wrote: >>> > On 31 May, 02:47, Wolfgang Weisselberg <ozcvgt...(a)sneakemail.com> > >> So there is no source of light with perfect parallel rays. > > So you try to deny that stars have perfect parallel rays for > the purpose of telescopes and optical lenses on Earth. No one heard of gravitational lensing ? The light coming from any star will be shaped by any large object so I can;t see how any light sources can be truly parallel to each other if they are apart they will have differing gravitational attractions to the nearest mass.
From: RichA on 3 Jun 2010 10:56 On Jun 3, 5:49 am, "whisky-dave" <whisky-d...(a)final.front.ear> wrote: > "Wolfgang Weisselberg" <ozcvgt...(a)sneakemail.com> wrote in message > > news:uraid7-2en.ln1(a)ID-52418.user.berlin.de... > > > DanP <dan.pe...(a)gmail.com> wrote: > >> On 2 June, 02:00, Wolfgang Weisselberg <ozcvgt...(a)sneakemail.com> > >>> DanP <dan.pe...(a)gmail.com> wrote: > >>> > On 31 May, 02:47, Wolfgang Weisselberg <ozcvgt...(a)sneakemail.com> > > >> So there is no source of light with perfect parallel rays. > > > So you try to deny that stars have perfect parallel rays for > > the purpose of telescopes and optical lenses on Earth. > > No one heard of gravitational lensing ? > There's never a mini black hole around when you need one.
From: Paul Furman on 3 Jun 2010 11:52 Wolfgang Weisselberg wrote: > > But with a well placed center pass ND lens you get perfect > bokeh, see Sony's 135mm STF (Smooth Transition Focus) lens. That's an interesting one I'd never heard of. http://www.the135stf.net/index.html Surprised I never heard of such a filter for screwing on the front. Probably doesn't work as well unless it's nested inside at the correct position.
From: Wolfgang Weisselberg on 3 Jun 2010 17:57 whisky-dave <whisky-dave(a)final.front.ear> wrote: > "Wolfgang Weisselberg" <ozcvgtt02(a)sneakemail.com> wrote in message >> DanP <dan.petre(a)gmail.com> wrote: >>> So there is no source of light with perfect parallel rays. >> So you try to deny that stars have perfect parallel rays for >> the purpose of telescopes and optical lenses on Earth. > No one heard of gravitational lensing ? Sure, but Earth's diameter is too small to detect any differences from parallel rays. You need Earth's orbit as a baseline to detect differences for close stars. -Wolfgang
From: whisky-dave on 4 Jun 2010 08:46
"Wolfgang Weisselberg" <ozcvgtt02(a)sneakemail.com> wrote in message news:q2lld7-h5u.ln1(a)ID-52418.user.berlin.de... > whisky-dave <whisky-dave(a)final.front.ear> wrote: >> "Wolfgang Weisselberg" <ozcvgtt02(a)sneakemail.com> wrote in message >>> DanP <dan.petre(a)gmail.com> wrote: > >>>> So there is no source of light with perfect parallel rays. > >>> So you try to deny that stars have perfect parallel rays for >>> the purpose of telescopes and optical lenses on Earth. > >> No one heard of gravitational lensing ? > > Sure, but Earth's diameter is too small to detect any differences from > parallel rays. But trh sun isn't. > You need Earth's orbit as a baseline to detect differences > for close stars. But the problem is how to you get two exactly parallel 'rays'. |