LSS SKU: Pre-Owned Astrotech AT-65 Quad


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This unique apochromatic ED quad refractor astrograph has a four lens/two group/two ED element fully-multicoated optical system. It uses an FPL-53 element in its apochromatic triplet objective lens, and has a separate field-flattening proprietary ED singlet lens at the rear of the optical tube. The very sensibly-priced Astro-Tech AT65EDQ astrograph provides an exceptionally flat field for very wide DSLR and CCD deep space images that are sharp edge-to-edge, with no need for a separate field flattener. While designed primarily as an astrograph, it can also be used visually with a 1.25" star diagonal and eyepieces. pochromatic quadruplet ED refractor optics: the objective lens is a 65mm (2.56") aperture, 420mm focal length, f/6.5 focal ratio triplet using an element of high quality FPL-53 ED (Extra-low Dispersion glass) to reduce spurious color halos and fringing to vanishingly low levels. In addition, there is a separate ED glass singlet lens at the rear of the optical tube that acts as a field flattener to eliminate the curved field typical of fast focal ratio doublet and triplet refractors. Stars are focused and point-like to the edges of the field. This built-in field flattener eliminates the need to buy the separate external field flattener that most refractors need to provide flat field images. Fully multicoated optics: All lenses have the latest state-of-the-art antireflection multicoatings matched to their glass types on all air-to-glass surfaces for high light transmission and excellent contrast. Dew shield: A self-storing retractable dew shield slows the formation of dew on the lens in cold weather to extend your undisturbed observing time. It also improves the contrast, similar to the effect of the lens shade on a camera lens, when observing during the day or when there is excessive ambient light at night, such as a neighbor's backyard security light. The 4.75 pound AT65EDQ measures a very compact 13" long with the dew shield retracted, and is only 14.25" long with it extended. Dual speed 2" rack-and-pinion focuser with 2" accessory holder and 1.25" accessory adapter, both with compression rings: The precision-made rack-and-pinion focuser has dual-speed focusing. There are two coarse focusing knobs. The right knob also has a smaller concentric knob with 10:1 reduction gear fine focusing ratio. This provides exceptionally precise image control during critical DSLR or CCD imaging. The focus knobs have ribbed gripping surfaces so they are easy to operate, even while wearing gloves or mittens in cold weather.
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