This finder scope has a 50mm aperture, and so provides a particularly bright image. Objects which you are not even able to see using just the naked eye will usually become directly visible. Also, if you are trying to locate one of the brighter DSOs, this will no longer be able to remain hidden, giving itself up to your searching eye. A star map with reference stars with which one can orient oneself is usually used to find particular objects. Some of the stars shown on star maps cannot be seen, or are difficult to see, with just the naked eye however. This finder scope makes a large number of aditional stars available - a big plus for being able to successfully locate objects.The Alstar 9x50 finder scope has built-in crosshairs to let you find the correct object more easily and to put it in the middle of the main telescope's field of view. The threads have been kept quite fine but are still very visible against the night sky nevertheless. The finder scope comes supplied complete with a robust mounting plate. Two adjustment screws and a compression spring allow very rapid alignment with the main telescope. Precise focusing can be achieved by rotating the objective lens. The finder scope will fit into a large range of holders: Skywatcher, Celestron, Vixen, Orion, GSO and many other makes have compatible finder scope shoes.