Sky-Watcher EQ5 MOUNT - Manual (Page 20)

20
PROPER CARE FOR YOUR TELESCOPE
C
ollimating a Newtonian reflector
Fig.q
Correctly aligned 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.q).
Fig.q-1
Fig.q-2
Fig.q-3
Fig.q-4
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.q-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.q-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.q-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
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.
Primary mirror
Support for
secondary mirror
Secondary mirror
Focuser