This is a great accessory for precisely collimating your Newtonian reflector telescope to achieve the best image the telescope can deliver, especially for faster systems (f/5 or lower).
This device allows you to adjust both of the telescope's mirrors with a simple, precise, two-step procedure. The collimator fits in the 1.25" focuser and emits a red laser beam into the telescope. Tilt the secondary mirror so that the red laser dot hits the center of the primary mirror. Then tilt the primary mirror so that the return beam hits the white plate angled at 45 degrees in the collimator's window. Adjust the mirror until the return beam lines up with the original beam. That's it! Your scope will be collimated for optimum performance with this high quality laser collimator in only one or two minutes!
Another leading company sells this same product for about $65 + shipping! The collimator is made of strong anodized aluminum and includes batteries. It features a large on-off switch that is easy to operate even with gloves on. Its small size makes it easy to store in your accessory case. If the laser is dropped or otherwise loses its collimation, it can be collimated (To avoid accidental miscollimation the adjustment screws are covered by silicone glue, but once needed the glue can be pulled out and the laser adjusted if necessary). Does not include an instruction sheet but these collimation instructions (pdf document) will work just as well.