Be careful, the focus mechanisms of some lenses will go past infinity and you'll end up with out of focus images. If you are trying to photograph constellations and such it would be best to do trial and error with manual focussing and check your result on your lcd. Don't touch your focus ring once you get a sharp image. I use a little dab of whiteout opposite the focus index to indicate where I get infinity on the lenses I use for star shots. (I use an EQ6 pro equatorial mount autoguided through an 80mm guide scope, a camera lens for wide field photos or a 5 inch apochromatic refractor telescope as a lens for deep space stuff. A 8 inch newt or a 6 inch cat is also sometimes used.)