Why they didn't use prisms/mirrors to shorten the focal length of Yerkes refractor telescope yet losing no power? - Quora
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MCA | Free Full-Text | Active Optics in Astronomy: Freeform Mirror for the MESSIER Telescope Proposal | HTML
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The Sunshield on NASA's James Webb Space Telescope is the largest part of the observatory five layers of thin membrane that must unfurl reliably in space to precise tolerances. Last week, for
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