Astro0Stuff ~ TelescopeMart.com
Mechanical / Optical Alignment
Position the secondary mirror rotationally under the focuser
Look through the focuser drawtube. Rotate the secondary holder and mirror until the reflection of the primary mirror is centered all around. Move towards or away from the focuser until the edge of the primary is just seen in the secondary. Insert the Astro Optics collimator and when the primary mirror reflection is centered, lock the secondary in place. This completes the mechanical alignment.
Figure 2. Rotational adjustment Adjust tilt of secondary mirror
Insert the Astro Optics collimator into the focuser. In this case you are using the collimator as a peep sight to keep your eye centered, or on axis. Adjust the secondary tilt so that the reflection of the primary mirror appears centered front to back and side to side in the secondary. If not, adjust the secondary lateral or rotational position to center, and then readjust tilt. Aligning the secondary becomes an iterative process, with each successive adjustment to lateral, rotational and tilt generating smaller changes to the placement of the secondary. When it is set up correctly, the reflection of the primary should appear centered in the secondary.
Adjust the tilt of primary mirror
Now that the secondary mirror is positioned, it's time to adjust the primary mirror to point in the correct direction so that the optical system becomes closed. By closed, we mean that the image at the focuser (your eye) reflects off the secondary to the primary and then the primary reflects light back to the secondary, which in turn reflects the light 90 degrees back to the focuser.
Optical Collimation with the Astro Optics Collimator 5
The open sky or a white wall work well to evenly illuminate the view. You can also illuminate the system by shining a flashlight directly at the primary mirror center spot. It helps to hold the light close to the center of the tube, next to the secondary mirror.
The primary collimation screws are now used to adjust the tilt of the primary so the reflection from the Astro Optics is centered on the primary mirror spot. By introducing a circle of light at the focuser, the reflection of that light will appear centered on the primary center spot when collimated. This is precisely what the Astro Optics collimator does. At this point, it becomes obvious why the center spot was cut square or triangular. It is much easier to see the corners of a square or triangular spot extend equally around the illuminated Astro Optics reflection when the two become superimposed. Just be sure the hole in the primary mirror spot is accurately centered to use the outer corners for final adjustment.
If you have aligned your secondary correctly, you will only need to tweak the primary at this time. Adjust the collimation screws until the illuminated circle in the Astro Optics is centered on the primary spot. When you get through, the small black dot in the center of the collimator will appear superimposed in the dot on the primary center spot. Figure 3 illustrates the collimated view. After using the Astro Optics , your Newtonian is now well collimated.