Swarovski 80 HD spotting scopes belong to the group of optical products with the highest level of quality where only couple of other products from premium European Brands can also be placed. They offer almost unrivaled optical properties and at the same time the highest build quality and unique design. Acronym HD stands for the high quality fluoride glass material out of which all lenses and other elements of optical construction are made of. This type of glass guaranties minimal light aberrations and minimizes other unwanted optical phenomena. Housings of these spotting scopes are filled with dry nitrogen so that there is now dew accumulation inside the scopes even at the lowest temperatures. Outer material of housing has a quality fell to it and is really nice to touch. All lens surfaces are coated with the most advanced multilayer coatings Swarovski Company had developed in the recent years. These coatings enhance the light transmission rate, color saturation and contrast. Focusing is done with the ring around the scope body which and because of high diameter of this ring focus settings can be really precise. STS stands for straight ocular position and ATS for angled ocular position.