Here's an extremely easy and inexpensive gadget I made.  Known as a "Hartmann Mask", it is placed over the end of the telescope and helps to achieve fine focus.  When the telescope is not in focus, the three holes produce three images (of a star, say).  As the focus knob is manipulated, the three images of the star will either converge or diverge, depending on the direction of twist of the focus knob.  The object is to manipulate the knob so that the three images converge to a single point.  Then the star is in focus and the mask can be removed.

The construction was simple.  I found one of those 5 gallon bucket lids at Home Depot for $0.99.  It measures a bit more than 12", which is just about the outside diameter of my 10" LX200.  I test-fit the lid on my 'scope, and found that the "gripper" portion around the underside of the circumference of the lid was in the way.  I cut away that extra plastic middle rim along with the bunch of little supporting ribs that stiffened it, using a Dremel cutting wheel.  What remained was a gap that I filled with one wide strip of felt followed by a narrower strip around the outside of the gap.  The lid then fit nice and snug on the end of the telescope, almost as good as the factory cover.

Finally, I cut the three holes.  The lid has a convenient little stump of plastic right in the middle, so I used that to locate one end of a compass in the center of the lid, and traced-out two circles: a smaller circle that matched the circumference of the telescope's small front mirror holder (the plastic cap-thing with three screws in it), and a larger circle that matched the circumference of the telescope's front aperture.  The gap between the two concentric circles was then the region I'd use to make the three circle cuts.  Using a 30-60-90 triangle, I laid out three lines from the center of the lid with 120 degree separation between them.  Then I found the centers of the three circles and used the sharp point on the compass to etch-out the three circles and cut them out with a razor blade.  After a little sanding, it was done.

So, for a total cost of $1.19 (the sheet of felt was $0.20), I have a durable and useful tool that really works (I need to snap some images to show what it looks like through the eyepiece).  I believe the performance of this homemade device is equivalent to a commercially-produced metal one I've seen advertised costing upwards of $45-55!

Update: I've since added a bit of duct tape on both sides to form holes shaped like rectangles, both to reduce the hole size (they were pretty big!) and to permit the formation of "light spikes" due to the rectangular shapes.  When the gain on the camera is turned way up, diffraction-type spikes will emanate from the brighter stars - good focus is achieved when the spikes line up with one another.   When the gain is reduced, the mask behaves normally - good focus is obtained when the three star images are merged.