Keep in mind that the sharpness and detail achieved in moon shots is greatly influenced by atmospheric conditions, probably much more so than lens sharpness. These super cheap, super long teles aren't actually that bad at the center of the frame as far as sharpness is concerned, although wide open they tend to display rather severe vignetting. The main limitations are lack of autofocus, lack of communication with camera in general, and very small max aperture (slow; good tripod/head combo is a must). They are a good way to experience super long focal lengths, without spending $10k+.