EvoGuide 50DX Doublet APO Refractor50 mm apochromatic refractor with matched lens assembly with one ED element 242 mm focal length f 4. 8 1. 25 Helical focuser Finder stalk V style dovetail with rings Prime focus ring The EvoGuide 50DX APO Guide Scope Astrograph takes Sky Watcher's doublet design and packages it in a lightweight guide scope. These doublet refractors deliver dramatic, coal black skies and faithful, contrast rich views of planetary and deep space phenomenon that are