Editing Binoculars (section)

==== Erecting lenses ====

In aprismatic binoculars with Keplerian optics (which were sometimes called "twin telescopes"), each tube has one or two additional lenses ([[relay lens]]) between the objective and the eyepiece. These lenses are used to erect the image. The binoculars with erecting lenses had a serious disadvantage: they are too long. Such binoculars were popular in the 1800s (for example, [[G. & S. Merz]] models). The Keplerian "twin telescopes" binoculars were optically and mechanically hard to manufacture, but it took until the 1890s to supersede them with better prism-based technology.<ref>{{cite conference |url=http://fp.optics.arizona.edu/antiques/History%20of%20Telescopes%20and%20Binoculars%20-%20SPIE.pdf |first1=John E. |last1=Greivenkamp |first2=David L. |last2=Steed |title=The History of Telescopes and Binoculars: An Engineering Perspective |book-title=Proc. SPIE 8129, Novel Optical Systems Design and Optimization XIV, 812902 |editor1=R. John Koshel |editor2=G. Groot Gregory |date=10 September 2011 |issn=0277-786X |doi=10.1117/12.904614 |s2cid=123495486 |archiveurl=https://web.archive.org/web/20141129083421/http://fp.optics.arizona.edu/antiques/History%20of%20Telescopes%20and%20Binoculars%20-%20SPIE.pdf |archivedate=2014-11-29 |url-status=live}}</ref><ref>{{Cite web |url=https://hinode-bino-guide.com/how-porro-prism-binoculars-work/ |title=How Porro Prism Binoculars Work |access-date=2022-10-08 |archive-date=2022-10-08 |archive-url=https://web.archive.org/web/20221008150334/https://hinode-bino-guide.com/how-porro-prism-binoculars-work/ |url-status=live }}</ref>