The difference between the LX5 and LX6 is the ability to add Meade's digital setting circles to the LX6. There is no port on the LX5. The LX6 with the CAT (Computer Aided Telescope) was the precursor to the LX200. You could get both LX5's and LX6's with an F6.3 OTA. Meade has alway used the LX__ designation for their worm gear driven scopes starting with the LX2 in the early 80's.