Our products are 100% authentic! Mount --- Nikon F mount. F-number --- 5.9 to 21. Focal length(tele side)---500mm-1700mm. Unlike an astronomical telescope, it can capture images in the same orientation.It is equivalent to a 500mm to 1700mm lens when converted to magnification. However, the f value is about the same. The lens of the camera adapter is clean. The lens of the fieldscope is clean. Please confirm the state with a photograph. International Buyers - Please Note.