Collimating The Optics - Orion StarBlast Instruction Manual

To use your CCD camera with the StarBlast, it must have a
1.25 inch "nosepiece". All Orion StarShoot cameras have this
nosepiece (Figure 3). Due to the large amount of inward focus
travel required, however, digital SLRs equipped with a 1.25"
nosepiece (via T-ring connection) will not reach focus in the
StarBlast Imaging OTA.
First, acquire and center the object to be imaged with an
eyepiece. Then, remove the eyepiece and insert your CCD
camera into the telescope's focuser. Secure the camera with
the thumbscrews on the focuser's drawtube. Use the focus
knob to bring the image into focus.
Figure 3.
To use a CCD camera with the StarBlast, the camera
must have a 1.25" nosepiece, like the Orion StarShoot Imaging
cameras.
a.
Figure 4. Collimating the optics.
like this. (b) With the collimation cap in place, if the optics are out of alignment, the view might look something like this.
Here, the secondary mirror is centered under the focuser, but it needs to be adjusted (tilted) so that the entire primary mirror
is visible. The secondary mirror is correctly aligned, but the primary mirror still needs adjustment. When the primary mirror
(d)
is correctly aligned, the "dot" will be centered, as in
4
1.25" nosepiece
drawtube
Reflection
of primary
mirror clip
When the mirrors are properly aligned, the view down the focuser drawtube should look
(a)
(e) .

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 4a. If anything
is off-center, proceed with the following collimating proce-
dure.
The Collimating Cap and Primary Mirror Center Mark
Your StarBlast comes with a collimating cap. This is a simple
cap that fits on the focuser drawtube like a dust cap, but has a
hole in the center and a silver bottom. This helps center your
eye so collimating is easy to perform. Figures 4b through 4e
assume you have the collimating cap in place.
In addition to the collimating cap, you'll notice a small ring
label on the exact center of the primary mirror. This "center
mark" allows you to achieve a very precise alignment of the
primary mirror; you don't have to guess where the center of
the mirror is. You simply adjust the primary mirror position
(described below) until the reflection of the hole in the col-
limating cap is centered inside the ring.
b.
d.
c.
e.
(c)