How do I collimate my AstroMaster Newtonian telescope by aligning the mirrors in daylight?
Collimation is the proper alignment of the optical elements–lenses and mirrors in your telescope. Collimation is important for getting the best out of your scope. Poor collimation will result in optical aberrations and distorted images. Collimation of a Newtonian The optical performance of most Newtonian reflecting telescopes can be optimized by re-collimating (aligning) the telescope's optics, as needed. Before collimating your telescope, take time to familiarize yourself with all its components. The primary mirror is the large mirror at the back end of the telescope tube. This mirror is adjusted by loosening and tightening the three screws, placed 120 degrees apart, at the end of the telescope tube. The secondary mirror (the small, elliptical mirror under the focuser, in the front of the tube) also has three adjustment screws. You will need an optional tool to perform collimation. To determine if your telescope needs collimation first point your telescope toward a bright wall or blue sky outside. Aligning the Secondary Mirror If you have an eyepiece in the focuser, remove it. Obtain a collimating tool for Newtonians, often called a collimating cap. Rack the focuser tube in completely, using the focusing knobs, until its silver tube is no longer visible. You will be looking through the focuser at a reflection of the secondary mirror, projected from the primary mirror. During this step, ignore the silhouetted reflection from the primary mirror. Insert the collimating cap into the focuser and look through it. With the focus pulled in all the way, you should be able to see the entire primary mirror reflected in the secondary mirror. If the primary mirror is not centered in the secondary mirror, adjust the secondary mirror screws by alternately tightening and loosening them until the periphery of the primary mirror is centered in your view. Do not loosen or tighten the center screw in the secondary mirror support, because it maintains proper mirror position. Aligning the Primary Mirror Now adjust the primary mirror screws to re-center the reflection of the small secondary mirror, so it’s silhouetted against the view of the primary. As you look into the focuser, silhouettes of the mirrors should look concentric. Repeat steps one and two until you have achieved this. Remove the collimating cap and look into the focuser, where you should see the reflection of your eye in the secondary mirror. Updated 12/19/13
Created On: Oct 07 2008 03:45 PM