Unlike Fluorite, ED glass is not affected by atmospheric contaminants and acids. The EDT lens is also perfectly matched to the characteristics of the fine-grained Technical Pan emulsions which have their peak sensitivity at 405nm. Wth our matching accessories, you can create impressive astrophotos on 35mm and 6 x 7cm film formats. The optical design of the 180mm EDT objective consists of a positive element of ED glass surrounded by two matching hard crown meniscus lenses. The two outer elements are chosen so that the combination is free of coma, spherical aberration and other higher-order aberrations.
All surfaces are spherical, which results in a very smooth overall figure.
Under steady viewing conditions, you will see a hard white Airy disc at focus surrounded by the first diffraction ring. Inside and outside of focus you will see an evenly Illuminated, expanded disc with concentric Fresnel rings, the outermost ring brighter and wider than the rest. We have incorporated several significant improvements to the tube assembly to make it easier to transport and set up in the field. The dewcap slides over the lens cell for more compact storage. An aluminum dust cover protects the optical surface when not in use, and a foam-fitted carrying case will help retain the beauty of your tube assembly for years.