Brandon eyepieces are a popular choice of professional astronomers worldwide. VernonScope estimates that over one million Brandons in various incarnations and focal lengths have been produced since their introduction in the early 1940s. Designed for medium to high power use with any telescope at focal ratios down to f/4, they are very sharp at the center (although somewhat less so at the edges) and ideally suited to 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 such as Venus, Mars, and 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. They have moderately wide apparent fields of view, of about 45°.
Brandons are threaded for Vernonscope filters only. The use of standard eyepiece color or nebula filters requires adapter #3405. They have rubber eyecups that roll down for eyeglass use, although their eye relief is quite short in the shorter focal lengths. Brandons are the sharpest design currently available in a 1.25" barrel size for eyepiece projection photography.
Related categories OPTICS AND OPTICAL PHENOMENA
TELESCOPE EQUIPMENT AND TECHNIQUES
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