12
4. Collimation
Collimation is the process of adjusting the mirrors so they are
correctly aligned with one another. Your telescope’s optics
were aligned at the factory, but they could become misaligned
during shipment. Accurate mirror alignment is important to
ensure the peak performance of your telescope, so it should
be checked regularly. Collimation is relatively easy to do and
can be done in daylight.
The Collimation Cap and Mirror Center Mark
Your XT PLUS comes with a “quick-collimation” cap (
Figure
21). This is a simple cap that fits on the focuser drawtube like a
dust cap, but has a hole in the center and a reflective material
on the underside. The cap helps center your eye so that col-
Figure 22.
The telescope ready for collimation, with the
tube oriented horizontally, the collimation cap in place on the
focuser, and a piece of white paper placed inside the tube
opposite the focuser.
Figure 23.
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.
Figure 21.
The quick collimation cap, which features a
reflective inner surface, helps in centering reflections of the
optics in the focuser during the collimation process.
