These professional-grade Vernonscope Brandon eyepieces are the only eyepieces made in the USA. They are hand-assembled, using four lenses of four different glass types (barium flint, lanthanum crown, light crown, and double extra dense flint). Their unsymmetrical duplet formulation (somewhat similar to the currently most expensive eyepieces in the world, the virtually unobtainable Zeiss Abbe Orthoscopics) was designed by Chester Brandon, one of the designers of the top-secret Norden bombsight that helped end World War II.
Vernonscope Brandons 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 eyepiece fads and fashions come and go.
Designed for medium to high power use with telescopes having focal ratios of f/7 and above, their magnification is constant from center to edge, with no pin cushion or barrel distortion. The Brandons have extremely high contrast and no ghosts. They have excellent color correction and very low astigmatism.
Brandons will also work with telescopes down to an f/4 focal ratio, with excellent on-axis performance that is very sharp at the center (although somewhat less so at the edges) for lunar, planetary, star cluster, and binary star observing – but their best performance comes at focal ratios f/7 and above.
The Brandons are fully coated, but not multicoated. This reduces 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 such as Venus, Mars or Jupiter. It also shows as a significant difference in the background darkness immediately surrounding a bright object, which is especially important for double-star observing. Brandons are accordingly noted for their exceptional contrast and extremely dark background, two reasons why Questar has been using them in their ultra-premium Maksutov-Cassegrain scopes since 1971.
The Vernonscope Brandon eyepieces come in two body styles – standard and flat top. The standard style has a rubber eyecup that shields the eye from ambient light when rolled up, rolling down for eyeglass use. Attaching an eyecup to the eyepiece body reduces the available eye relief, however, as the eye lens of the eyepiece must be recessed somewhat to provide a lip for attaching the eyecup. The flat top Brandon versions have no eyecups. Their eyelens is virtually flush with the smooth top and rounded edge of the eyepiece body. Since the eye lens is no longer recessed, the observer has full access to all of the designed eye relief.
The Vernonscope Brandons are threaded for Vernonscope filters only. The use of standard eyepiece color or nebula filters requires an adapter. Brandons are the sharpest design currently available in a 1.25" barrel size for eyepiece projection photography.