"The Baader Planetarium Sky Surfer III offers several advantages over the typical low-cost red dot finders. The extra-large 30 mm optical aperture and improved optical quality delivers a much larger undistorted view and razor-sharp red dot. Unlike many red-dot finders, the Sky Surfer III incorporates optimized anti-reflective lens coatings which deliver proper locator dot brightness with virtually no image dimming. One other new feature you will really come to appreciate is the extra-long lens housing, which acts as a shield to effectively prevent dewing.Mounting and adjustment of the Sky Surfer is simple. Elevation and Azimuth adjustment is accomplished by turning the two knurled adjustment knobs. The red locator dot intensity is adjusted by a knurled adjusting knob. Attachment to your telescope is also straightforward, with all necessary parts included. Simply attach a base to your telescope, slip on the finder and tighten the two dovetail clamp screws.Three bases are included. The short base works best for large tubes. It includes two mounting slots (for screw mounting) and may also be attached with double sided foam tape (supplied). The taller base fits smaller diameter tubes (as well as large tubes using the included spacer plate) and the slotted holes accommodate the factory hole pattern of popular SCTs. The third base fits the Vixen finder dovetail standard used on many import refractors. Each Sky Surfer includes a replaceable 3 V lithium battery for ext|Comfortable sized viewing screen for all lighting conditions|Variable Intensity Light Controls|Unique design features eliminate glare and prevent dew|Compatible with spotting scopes and mounted binoculars"