drawtube
Reflection of primary mirror clip
a.
b.c.
d.e.
Figure 10. Collimating the optics. (a) When the mirrors are properly aligned, the view down the focuser drawtube should look like this. (b) With the collimation cap in place, if the optics are out of alignment, the view might look something like this. (c) Here, the secondary mirror is centered under the focuser, but it needs to be adjusted (tilted) so that the entire primary mirror is visible. (d) The secondary mirror is correctly aligned, but the primary mirror still needs adjustment. When the primary mirror is correctly aligned, the “dot” will be centered, as in (e).
Appendix A: Collimating (Aligning the Mirrors)
Collimating is the process of adjusting the mirrors so they are aligned with one another. Your telescope’s optics were aligned at the factory, and should not need much adjust- ment unless the telescope is handled roughly. Accurate mirror alignment is important to ensure the peak perfor- mance of your telescope, so it should be checked regularly.
Collimating is relatively easy to do and can be done in day- light.
To check collimation (mirror alignment), remove the eye- piece and look down the focuser (4). You should see the secondary mirror (17) centered in the drawtube, as well as the reflection of the primary mirror (16) centered in the secondary mirror, and the reflection of the secondary mirror (and your eye) centered in the reflection of the primary mir- ror, as in Figure 10a. If anything is
The Collimation Cap and Mirror Center Mark
Your StarBlast 6 comes with a collimation cap (18). This is a simple cap that fits on the focuser like a dust cap, but has a hole in the center and a silver bottom. This helps center your eye so that collimating is easy to perform. Figures 10b, c, d, and e assume you have the collimation cap in place.
In addition to the collimation cap, the primary mirror is marked with a ring exactly at the center of the primary mir- ror. This is of great help in collimating the primary mirror since you can center the dot of the collimation cap in the middle of the ring.
Note: The center ring sticker need not ever be removed from the primary mirror. Because it lies directly in the shadow of the secondary mirror, its presence in no way adversely affects the optical performance of the telescope or the image quality.
Aligning the Secondary Mirror
With the collimation cap in place, look through the hole in the cap at the secondary (diagonal) mirror. Ignore the reflec- tions for the time being. The secondary mirror itself should be centered in the focuser drawtube, in the direction parallel to the length of the telescope. If it isn’t, as in Figure 10b, it must be adjusted. This adjustment will rarely, if ever need to be done.
It helps to adjust the secondary mirror in a brightly lit room with the telescope pointed towards a bright surface, such as white paper or wall. Also placing a piece of white paper in the telescope tube opposite the focuser (in other words, on the other side of the secondary mirror) will also be helpful in collimating the secondary mirror. Using a 2mm hex key, loosen the three small alignment set screws in the center hub of the
Note: When making these adjustments, be careful not to stress the spider vanes or they may bend.
When the secondary mirror is centered in the focuser draw- tube, rotate the secondary mirror holder until the reflection of the primary mirror is as centered in the secondary mirror as possible. It may not be perfectly centered, but that is OK.
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