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Refracting telescope - Wikipedia
ESCHENBACH Monocular Kepler System Magnification Distance 4.2x Near 5.5x 10mm 4026158139771 | eBay
Refracting telescope - Wikipedia
History of Science Society -- Committee on Education
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Engraving depicting the arrangement of lenses in Johannes Kepler's telescope. This had two double convex lenses and gave a wider field of view. Johannes Kepler (1571-1630) a German mathematician, astronomer, and astrologer.