18
adjustment, again moving the bull's-eye toward the center of the annulus. Repea t this rotation until the bull's-eye is
similarly placed toward the central dot in both positions and as close to the center as possible. Then, rotate the nose
assembly 90° and repeat the above procedure at 180° until you are satisfied that both positions are equally aligned
with respect to the central dot of the Cheshire.
Continue to rotate the nose assembly and make adjustments until the bull's-eye of the primary mirror appears within
the central dot of the annulus throughout a complete rotation.
When you have achieved this, the telescope is
collimated. (See the following illustration.)
Image visible in Cheshire eyepiece when the system is properly collimated
If, after repeated adjustments you still cannot adjust the primary mirror into collimation, the problem is likely to be
misalignment of the secondary. Check the secondary to determine whether it must be raised, lowered, rotated or
tilted. While this process may require several repetitions the first few times, you will find that, with practice, you can
quickly determine what adjustments to make to the secondary mirror by observing the location of the bull's-eye with
respect to the central dot as you rotate the nose assembly. Once you are familiar with the process, fine-tuning the
collimation can be accomplished in just a few minutes.
Use of the Auto-Collimator
An auto-collimator eyepiece is available from Tectron, along with three tools and an instruction booklet. By following
instructions provided with the auto-collimator, you can make final, ever-so-slight adjustments to the secondary mirror,
if necessary. The auto-collimator is not intended, however, for use in making adjustments to the primary mirror. To
adjust the primary mirror, follow the steps outlined in the section above—
Use of the Cheshire Eyepiece
.
Image seen in the auto-collimator eyepiece when the NGT is properly collimated
Summary of Contents for NGT-12.5
Page 2: ......
