These eyepieces have been made in the USA for Questar by VernonScope since 1971.
They use four lenses in an unsymmetrical duplet formulation created by Chester Brandon, one of the designers of the top-secret Norden bombsight that helped end World War II. They are the choice of professional astronomers world-wide.
VernonScope estimates that over one million Brandons in various incarnations and focal lengths have been produced since their introduction in the early 1940s, proving that a good design endures, while optical fads and fashions come and go.
They are very sharp at the center (although somewhat less so at the edges) for superb lunar, planetary, star cluster, and binary star observing. They have excellent color correction and very low astigmatism, with very minor field curvature and ghosting. They are fully coated, but not multicoated, in order to reduce a phenomenon known as "narrow angle light scatter" that is sometimes seen in multicoated optics. This scatter shows as a loss of contrast and subtle details within bright objects like Venus, Mars, or Jupiter. It also shows as a significant drop in the background darkness immediately surrounding a bright object, which is especially important for double-star observing.
The eyepieces are designed to thread into the diopter tube of Questar telescopes for visual use and into the Questar camera coupling set for eyepiece projection photography, but will also fit into any 1.25” focuser or star diagonal. They are threaded to accept Vernonscope filters only. Their rubber eyecups roll down for eyeglass use, although their eye relief is quite short in the shorter focal lengths.