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 a silver 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!
The collimator is made of strong anodized aluminum and requires three LR44 type batteries (included). This new deluxe model now includes a rubber grip placed around the laser assembly within the collimator housing that helps the collimator retain its alignment if bumped or when batteries are replaced. Does not include an instruction sheet but these collimation instructions (pdf document) will work just as well.