| This short focal length Takahashi eyepiece uses a six lens/three group optical design to provide a high magnification capability with exceptional sharpness and contrast. The eyepiece consists essentially of an Abbe-type four-element longer focal length orthoscopic component positioned behind a doublet Barlow that uses an ED (Extra-low Dispersion) glass element for peak color correction. The Barlow shortens the effective focal length of the eyepiece to 3.6mm, while maintaining the greater eye relief typical of the longer main ortho component. The orthoscopic component provides the high contrast, low ghosting, flat field, and edge to edge image sharpness for which Abbe-type orthos are justly famous. The ED Barlow component provides higher magnification without adding or subtracting anything from the ortho’s superb color correction. The 3.6mm Takahashi makes an excellent lunar and planetary eyepiece for the new generation of affordable fast focal ratio apochromatic refractors, as well as Schmidt-Newtonian and Dobsonian reflectors with focal ratios of f/8 and under. It will typically provide excessively high powers with scope focal ratios longer than f/10 and is not recommended for scopes in this range. |
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