I'm having trouble focusing my NexStar SE telescope
April 10, 2018
Your NexStar SE has a focusing knob on the back of the tube assembly. Unlike a refractor or reflector, the SE scopes achieve focus by moving the primary mirror forwards and back on a spindle that also serves as a baffle inside the main scope tube.
While focusing the scope is largely intuitive, it may come out of the box out of focus. Here’s how to focus it:
Use your lowest power, longest focal-length eyepiece; turn the knob left to get closer to infinity focus, right for close focus (roughly 20 feet). (Reverse these directions for the 4SE.) Never turn the knob beyond the point where resistance is encountered, or you may damage the focusing mechanism.
Note: The focusing knob has a black rubber cover. If the focus is rough or loose, it may be the cap and not the mechanism. Check that the cap isn’t pressed against the metal on the back of the tube. Pull it back slightly if it is. If the cap is too loose, the knob may need to be shimmed to make the cap fit tightly enough so that it doesn’t slip. Replace or remove the cap entirely if these suggestions do not work.