Precautions for installation of guide rail base: 1. Remove the screws from the lens barrel and replace them with the long screws provided. Keep the original screws in place for future use. 8SE, C8/C8HD have one screw at the objective end, two screws at the eyepiece end 2. First, tighten the screws by hand. If the screws cannot be fully inserted or cannot be tightened after a few turns, it is possible that the screws have been selected incorrectly. Do not force the installation again. 3. For the end with two screws, do not tighten one side at a time when tightening the screws. Tighten evenly multiple times. If one side is tightened at a time, the other side may not be able to tighten the screws, or the screws may not be fully tightened, which can pose a safety hazard. C8/C8HD rail mounting steps: 1. Remove the screws on the main mirror. 2. Align the star guide slot LOGO outwards with the empty space after dismantling the main mirror, as shown in the picture. 3. Install the screws in the corresponding spaces. C8/C8HD are 1 screw at the objective lens end and 2 screws at the eyepiece end. 4. Fixed rail slot, the dove tail plate installed to the middle of the slot 5. Installation screws fixed, complete!