Now you can get a complete guidescope package from Celestron which includes both 80mm refractor and 125mm rings. No need to fumble in the dark with an uncomfortable diagonal, because the included extension tube helps you to easily reach focus. What's more, it's also compatible with the Celestron NexGuide Autoguider by sliding it in - or threading it directly on! The quality 80mm refractor guidescope with a 600mm focal length and focal ratio of f/7.5 includes a metal focuser with tension screw to help to minimize mechanical "play" when focusing.