Orion starBlast 4.5 EQ - Manual (Page 9)

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6. collimating the optics
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 adjustment unless
the telescope is handled roughly. Accurate mirror alignment is
important to ensure peak performance of your telescope, so it
should be checked regularly. Collimating is relatively easy to
do and can be done in daylight.
To check optical alignment, remove the eyepiece and look
down the focuser drawtube. You should see the secondary
mirror centered in the drawtube, as well as the reflection of
the primary mirror centered in the secondary mirror, and the
reflection of the secondary mirror (and your eye) centered in
the reflection of the primary mirror, as in Figure 9a. If anything
is off-center, proceed with the following collimating procedure.
Figure 8. This illustration show the telescope pointed in the four cardinal directions (a) north (b) south (c) east (d) west. Note that the
tripod and mount have not been moved; only the telescope tube has been moved in the R.A. and Dec. axes.
a b c d
drawtube
Reflection
of primary
mirror clip
Figure 9. 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) .
a.
b. c.
d. e.