Dan-- . If the hole is very small compared to the projection-distance, then the image of the Sun projected on the wall would be sharp and clear-edged, nearly free of fuzziness. Its size will be about 1/100 of the projection-distance. . The un-fuzziness of a small-aperture projection is the reason why they're used to get precise Solar noon from a noon-mark. . Englarging the aperture enlarges the image by the same amount, and of course makes it fuzzier, because each little element of the previous image is now duplicated over a region the size of the aperture. . In your example, the aperture is about twice the size of the tiny-aperture image. . Michael Ossipoff Aprilis 8th, 2020 Aries 20th 16 W
. On Wed, Apr 8, 2020 at 12:05 PM Dan-George Uza <cerculdest...@gmail.com> wrote: > Hello, > > I'm a big fan of meridian lines inside churches and I know these are sort > of camera obscura sundials. > > While I understand the geometry behind pinhole camera projections I can't > seem to find any help on how the solar image forms after the rays pass a > sizeable aperture nodus (for example a vertical 25cm nodus projected onto a > wall 10 meters away) and how the ratio of hole size vs. projection distance > affects the size and fuzzyness of the final projected image. So what's the > geometry behind that? > > > PS: Some sources refer to the projected image as "stenopaic image". Is > this universally acceptable? > > -- > Dan-George Uza > --------------------------------------------------- > https://lists.uni-koeln.de/mailman/listinfo/sundial > >
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