Features: -Fits in 1.25" focusers and easy to use;simply cap the telescope, remove the diagonal, and place the eyepiece directly in the focuser. -For aligning optics of Newtonian reflectors, Dobsonian reflectors, and Schmidt-Cassegrain Telescopes (SCTs). -The short collimator for mirror (reflector) telescopes has a 45 degree plate for easier visual accuracy. -Item was made by aluminum with crosshair at the bottom allow quick and precise centering of the optics. -This collimation eyepiece can be used for precisely collimating the Newtonian and Schmidt-Cassegrain reflector telescopes for better image quality. To get the most out of your Newtonian scope you really need to align or collimate the mirrors. It can take some time getting used to aligning both the secondary and primary mirrors and this short collimator can make it much easier. The short collimator for mirror (reflector) telescopes has a 45 degree plate for easier visual accuracy. Collimation is the alignment of elements inside an optical system like a telescope. Colimating a telescope consists of adjusting the tilt and position of the mirrors and lenses to ensure that the focal point reaches optimum focus at the point from which the image will be viewed (the eyepiece or possibly a camera). Specifications: Material: Aluminum Metal Structure Size: 32mm * 65mm / 1.25in * 2.56inch Package include: 1 * Collimating Eyepiece