| Designed by Thomas M. Back, noted apochromatic refractor designer, this short focal length eyepiece is outstanding for high power observing with medium and long focal ratio refractors, reflectors, or catadioptric scopes – even under average seeing conditions. It is optimized for observing bright objects with minimum aberrations, both on and off axis, while showing maximum detail and definition. It has very high light transmission, very high contrast, minimal lateral color, and minimal light scatter. For Dobsonian users and others without tracking drives, the very low lateral color and other aberrations allow a planet to drift across the entire field while still being sharp and having high contrast, thereby maximizing observing time. While the eyepiece is optimized for observing subtle lunar and planetary detail, the eyepiece’s observing virtues work equally well for splitting binary stars, resolving globular clusters, showing subtle nebular contrast, etc. A light coating of lubricant has been applied to the threads in the eyepiece’s twist-up eyecup. If any lubricant is visible on the inner eyepiece body when the twist-up eyecup is in the extended position, remove the excess lubricant with a clean wipe, such as a tissue. Operate the twist-up eyecup several times, cleaning the body as necessary until no more lubricant is visible on the eyepiece body when the twist-up eyecup is fully extended.
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