Yrjö Väisälä

Yrjö Väisälä (; 6 September 1891 – 21 July 1971) was a Finnish astronomer and physicist.

Optician

He developed several methods for measuring the quality of optical elements, as well as a lot of practical methods of manufacturing said elements. This allowed the construction of some of the earliest high-quality Schmidt cameras, in particular a "field-flattened" version known as Schmidt-Väisälä camera. Contemporary to Bernhard Schmidt's design, but unpublished was also Prof. Yrjö Väisälä's identical design which he had mentioned in lecture notes in 1924 with a footnote: "problematic spherical focal surface". in honour of its founder. The lunar crater Väisälä is named after him, and so are the minor planets 1573 Väisälä and 2804 Yrjö.