C
ollimating a Newtonian reflector
15
Fig.j
Corretly aligned
Primary mirror
Support for
secondary mirror
Secondary mirror
Focuser
Needs collimation
Primary mirror clip
Ignore the reflected
image for now
Primary mirror clip
Primary mirror clip
Primary mirror clip
Adjusting screw
Primary
mirror
Mirror cell
Locking screw
Collimation is the process of aligning the mirrors of your
telescope so that they work in concert with each other to
deliver properly focused light to your eyepiece. By
observing out-of-focus star images, you can test whether
your telescope's optics are aligned. Place a star in the
centre of the field of view and move the focuser so that
the image is slightly out of focus. If the seeing conditions
are good, you will see a central circle of light (the Airy
disc) surrounded by a number of diffraction rings. If the
rings are symmetrical about the Airy disc, the
telescope's optics are correctly collimated (Fig.j).
If you do not have a collimating tool, we suggest that you
make a "collimating cap" out of a plastic 35mm film
canister (black with gray lid). Drill or punch a small
pinhole in the exact center of the lid and cut off the
bottom of the canister. This device will keep your eye
centered of the focuser tube. Insert the collimating cap
into the focuser in place of a regular eyepiece.
Collimation is a painless process and works like this:
Pull off the lens cap which covers the front of the
telescope and look down the optical tube. At the bottom
you will see the primary mirror held in place by three
clips 120º apart, and at the top the small oval secondary
mirror held in a support and tilted 45º toward the focuser
outside the tube wall (Fig.j-1).
The secondary mirror is aligned by adjusting the three
smaller screws surrounding the central bolt. The primary
mirror is adjusted by the three adjusting screws at the
back of your scope. The three locking screws beside
them serve to hold the mirror in place after collimation.
(Fig.j-2)
Aligning the Secondary Mirror
Point the telescope at a lit wall and insert the collimating
cap into the focuser in place of a regular eyepiece. Look
into the focuser through your collimating cap. You may
have to twist the focus knob a few turns until the
reflected image of the focuser is out of your view. Note:
keep your eye against the back of the focus tube if
collimating without a collimating cap. Ignore the reflected
image of the collimating cap or your eye for now, instead
look for the three clips holding the primary mirror in
place. If you can't see them (Fig.j-3), it means that you
will have to adjust the three bolts on the top of the
secondary mirror holder, with possibly an Allen wrench
or Phillip's screwdriver. You will have to alternately loosen
one and then compensate for the slack by tightening
the other two. Stop when you see all three mirror clips
(Fig.j-4). Make sure that all three small alignment screws
are tightened to secure the secondary mirror in place.
Fig.j-1
Fig.j-2
Fig.j-3
Fig.j-4
Summary of Contents for SK P25012EQ6-2IN
Page 1: ...SK P25012EQ6 2IN...
