The AXJ Encoders Set allows you to greatly improve tracking performance of the Vixen Optics AXJ equatorial mount. The encoders assure the position of the mount indicated on the controller corresponds with the direction of the telescope. You will be able to enjoy easier GoTo slewing by loosening the clamp levers and moving the optical tube by hand. The encoders also watch the tracking motion of the AXJ equatorial mount in the resolution of 0.1 arcsecond for a higher level of accuracy. Subtle periodic errors can be detected for corrections and extremely precise tracking is the result—periodic error typically less than 0.5 arcseconds. The right ascension and declination sensors fit inside the mount and do not affect its dimensions.