9
center your eye so that collimation is easy to perform.Figures
6b through 6e assume you have the collimation cap in place.
In addition to providing the collimation cap, you’ll notice a tiny
ring (sticker) in the exact center of the primary mirror.This
“center mark”allows you to achieve a very precise collimation
of the primary mirror; you don’t have to guess where the cen-
ter of the mirror is. You simply adjust the mirror position
(described below) until the reflection of the hole in the colli-
mation cap is centered inside the ring. This center mark is
also required for best results with other collimating devices,
such as Orion’s LaserMate Laser Collimator, obviating the
need to remove the primary mirror and mark it yourself.
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 tele-
scope or the image quality.That might seem counter-
intuitive, but it’s true!
Aligning the Secondary Mirror
With the collimation cap in place, look through the hole in the
cap at the secondary (diagonal) mirror. Ignore the reflections
for the time being.The secondary mirror itself should be cen-
tered in the focuser drawtube, in the direction parallel to the
length of the telescope. If it isn’t, as in Figure 6b, 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 toward a bright surface, such as
white paper or wall.Placing a piece of white paper in the tele-
scope tube opposite the focuser (i.e., on the other side of the
secondary mirror) will also be helpful in collimating the sec-
ondary mirror. Use a Phillips head screwdriver to loosen the
three small alignment screws in the center hub of the 3-vaned
spider several turns.Now hold the mirror holder stationary (be
careful not to touch the surface of the mirrors), while turning
the larger center screw with a Phillips head screwdriver (see
Figure 7).Turning the screw clockwise will move the second-
ary mirror toward the front opening of the optical tube, while
turning the screw counter-clockwise will move the secondary
mirror toward the primary mirror.
When the secondary mirror is centered in the focuser draw-
tube, rotate the secondary mirror holder until the reflection of
a.b. c.d. e.
Figure 6. 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 primar y mirror is correctly aligned, the
“dot”will be centered, as in (e).
Figure 7. To center the secondary mirror under the focuser, hold
the secondary in place with your fingers while adjusting the primary
screw with a Phillips head screwdriver.Do not touch the mirror’s
surface.