Equipped with an oversized aperture and a powerful zoom range, the Celestron 18-40x80 SkyMaster Zoom Binoculars are an ideal choice for long-duration astronomical or long-distance terrestrial (land) use. The large objectives ensure volumes of light are gathered to see better than smaller-aperture models, and the easy zoom lever allows you to set the binoculars on low power to easily find your subject, then zoom in to make detailed up-close observations. These binoculars were engineered with an exceptionally long eye relief to make them comfortable to look through for extended periods of time, while limiting eye strain. Because of the size and weight of the SkyMaster binoculars, Celestron engineered them with a center stabilizer bar and an adjustable tripod mount to provide a hands-free option and relieve arm strain, reduce fatigue, and limit vibrations.