Viking Swallow ED 65mm Spotting Scope. Building on the success of their Swallow 65mm and 80mm models, Viking have introduced an even more advanced Spotting Scope with superior optical performance. From the extra-low dispersion (ED) glass objective elements to the dielectric coatings on the prisms, these spotting scopes perform to a level not seen in instruments at this price point before.. High Quality ED Glass. Unlike their predecessors the Viking Swallow ED comes equipped with high-quality Extra-low Dispersion (ED) glass. ED glass is specially formulated and helps to greatly reduce chromatic aberration so that you experience little to nocolour fringing. This means that the Swallow ED produces sharper images with better contrast and due to the better light transmission outstanding true-to-life colour. These differences become even more apparent when lighting conditions are dim, like at dawn or dusk.. Dual-focus for precision tuning. Another advantage of the Swallow ED Spotting Scop