4 ms·
The whole Hubble mirror fiasco was fascinating. The before and after images of the galaxy M100 in the following link outlines the extent of the error: https://
by gadnuk 5y ago
The whole Hubble mirror fiasco was fascinating. The before and after images of the galaxy M100 in the following link outlines the extent of the error:
https://www.nasa.gov/content/hubbles-mirror-flaw https://www.nasa.gov/content/hubbles-mirror-flaw
One may assume that maybe the error was simply too big and that's why the aberration. Here's the root cause and the magnitude of the error would be dismissed as nothing by most people on this planet but ultimately turned out to be huge!
"Ultimately the problem was traced to miscalibrated equipment during the mirror's manufacture. The result was a mirror with an aberration one-50th the thickness of a human hair, in the grinding of the mirror."
- a9h74j 5y agoThat's huge. Everyday profile accuracy can be spoken of in "quarter wavelength"-like terms.
- xxpor 5y agoWas that true in 1979?
- HPsquared 5y agoAccuracy less than a wavelength has been possible for a long time: https://en.wikipedia.org/wiki/Foucault_knife-edge_test https://en.wikipedia.org/wiki/Foucault_knife-edge_test
- xxpor 5y agoHuh wow, that's brilliant! I was expecting something super complicated with extremely high tech sensors.
- a9h74j 5y agoSpherical-against-spherical and flat-against-flat grinding can be self-truing, so in effect centuries-old clever results required clever testing to verify. High tech in those days? Rumor I heard in the mid-1980s was that LLNL had [vertical?] lathes which could mechanically cut mirrors to optical-profile accuracy. Supposedly 100gpm liquid flows were required to keep the part temperatures uniform.