Image: JohnWall
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Description: John Wall - retired design engineer Inventor of the Crayford focuser. ATM, optical research , painting, making things. Writing articles. Inventor of the Zerochromat retrofocally corrected refractor, discoverer of a new refractor concept, the Hypochromat.
Title: JohnWall
Credit: Own work / At my request was donated by Mr John Wall (wallporritt(at)madasafish.com) to Wikipedia.
Author: Tamasflex / John Wall
Usage Terms: Creative Commons Attribution-Share Alike 3.0
License: CC BY-SA 3.0
License Link: https://creativecommons.org/licenses/by-sa/3.0
Attribution Required?: Yes
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