Orion STARBLAST 6 9964 - Manual (Page 10)

10
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 off-center, as in Figure
10b, proceed with the following collimation procedure.
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 4-vaned spider several turns. Now hold the sec-
ondary mirror holder stationary (be careful not to touch the
surface of the secondary mirror), while turning the center
screw with a Phillips head screwdriver (See Figure 11).
Turning the screw clockwise will move the secondary mirror
toward the front opening of the optical tube, while turning
the screw counter-clockwise will move the secondary mirror
toward the primary mirror.
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.
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).