How to Collimate a Newtonian Telescope

Preparation

• 1

  Remove the protective cap from the optical tube assembly. Shine a flashlight down the tube and examine the primary mirror.

• 2

  Look for a small circle or dot in the center of the mirror. If your mirror lacks a center marker, carefully remove the mirror from the tube and add a small dot or circle in the exact center with a sticker or paint. Consult the owner's manual for specific instructions on how to remove the mirror.

• 3

  Tilt the telescope tube at a 45 degree angle. Remove the protective cap from the focuser and insert the Cheshire sight tube.

Collimation

• 4

  Check the alignment on the secondary mirror. Look through the sight tube and turn the focuser knob until the secondary mirror almost fills the field of view. Check whether the outer edge of the mirror is centered in the field of view. The mirror should appear uniformly round as well.

• 5

  Align the secondary mirror if it is off-center. To lower the secondary in the field of view, loosen the central screw on the mirror, and then tighten the three surrounding screws to lock it in place. If you need to raise the mirror, loosen the three surrounding screws and tighten the central screw to lift it upward.

• 6

  Adjust the tilt on the secondary mirror by loosening one of the three screws surrounding the central screw. Observe how this affects the tilt by looking through the sight tube. Adjust the other screws as necessary until the secondary appears perfectly centered and round.

• 7

  Look through the sight tube and check that the center marker on the primary mirror appears perfectly centered in its reflection in the secondary mirror. The Cheshire sight tube features two intersecting lines that mark the precise center of the field.

• 8

  Adjust the three thumbscrews on the primary-mirror end of the telescope until the marker appears centered in the field of view.