The Rubin telescope, like all larger telescopes, doesn't have a lens. It has a 27ft main mirror. I think the big difference is the size of secondary mirror whic

The Rubin telescope, like all larger telescopes, doesn't have a lens. It has a 27ft main mirror. I think the big difference is the size of secondary mirror which is 11ft in diameter. It can be compared to the neighboring Gemini South telescope which is similar size but has 3ft secondary and f16 focal length.