From the ManufacturerLarge 50mm diameter black finder scope lets you see fainter objects compared to smaller finder scopes. 9x magnification and a standard inverted 5.5 degrees field of view with superimposed crosshairs makes it easy to aim your telescope. Big 50mm objective lens collects more light than smaller finder scopes so you can detect more objects to train your telescope on. Includes a cast-aluminum bracket with innovative X-Y aim adjustment and a dovetail foot that fits most telescopes. Dovetail mounting base available (sold separately) for installation of 9x50 finder scope on any telescope