Making a concave mirror using 15th century technology (2018)
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Making a concave mirror using 15th century technology (2018)
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Re: Making a concave mirror using 15th century technology (2018)
#2With very simple tools (and quite a bit of patience) it is possible to make spherical and parabolic mirrors that deviate from the true shape by (much) less than one wavelength of light, which is rather impressive.
Re: Making a concave mirror using 15th century technology (2018)
#3(If the navigation is confusing, this is a subsection of chapter 3 (in the ToC sidebar). The parameters for [Lorenzo] Lotto's hypothetical telescope are derived in chapter 5, from an analysis of one of his paintings (!)).
Re: Making a concave mirror using 15th century technology (2018)
#4Nice.
On an aside, I'd recommend the YouTube channel Huygens Optics https://www.youtube.com/@HuygensOptics for all sorts of stuff to do with grinding decent optics.
Re: Making a concave mirror using 15th century technology (2018)
#5There is of course one thing here that isn’t 15th century technology! Aluminum, which was unavailable before the early 20th century. Brass or silver are better choices (or silver plate on brass)
Re: Making a concave mirror using 15th century technology (2018)
#6I forget the name, but some old paintings contain a visual equivalent of Rot-13, in that there are bits which look like odd blobs when viewed normally, but resolve to an image when viewed at the right angle or with a properly shaped mirror.
Anyone remember the proper term for this, or which century it was popular?
Re: Making a concave mirror using 15th century technology (2018)
#7I forget the name, but some old paintings contain a visual equivalent of Rot-13, in that there are bits which look like odd blobs when viewed normally, but resolve to an image when viewed at the right angle or with a properly shaped mirror. Anyone remember the proper term for this, or which century it was popular?
Hans Holbein’s “The Ambassadors” [1] is the one that immediately comes to mind. It has memento mori which is heavily skewed.
Re: Making a concave mirror using 15th century technology (2018)
#8I forget the name, but some old paintings contain a visual equivalent of Rot-13, in that there are bits which look like odd blobs when viewed normally, but resolve to an image when viewed at the right angle or with a properly shaped mirror. Anyone remember the proper term for this, or which century it was popular?
Hans Holbein’s “The Ambassadors” [1] is the one that immediately comes to mind. It has memento mori which is heavily skewed. [1] https://en.wikipedia.org/wiki/The_Ambassadors_(Holbein)
Anamorphosis, thanks, and same time frame: https://en.wikipedia.org/wiki/Anamorphosis#Renaissance
Re: Making a concave mirror using 15th century technology (2018)
#9With very simple tools (and quite a bit of patience) it is possible to make spherical and parabolic mirrors that deviate from the true shape by (much) less than one wavelength of light, which is rather impressive. https://en.wikipedia.org/wiki/Foucault_knife-edge_test
the candle and knife edge needed for the interferometry are indeed quite widely available in human history, but the necessary knowledge of the wavelike behavior of light is only about 200 years old
Re: Making a concave mirror using 15th century technology (2018)
#10There is of course one thing here that isn’t 15th century technology! Aluminum, which was unavailable before the early 20th century. Brass or silver are better choices (or silver plate on brass)
late 19th
early 19th, as a powder