Collimating A Refractor (With The Adjustable Objective-Lens Cell); Cleaning Your Telescope - SKY-WATCHER EQ3-2 Instruction Manual

Collimation is the process of aligning the lenses of your
telescope so that the light they collect will focus at the right spot
at the back of your telescope for your eyepieces to work.
Collimation is a simple process and works like this:
Pull off the dew cap at the front of your telescope and look into
the scope. The pair of lenses are held in a cell by a threaded
ring. This cell is held in place by three pairs of screws spaced
120 degrees apart. The larger Phillip's head screws actually
hold the cell on, while the smaller, buried Allen screws push
against a ledge at the front of the tube and allow the cell to tilt
slightly, by tension against the Phillips screws (Fig.r). The idea
is to alternately loosen and tighten each against the other until
you have a round star image.
There are a number of devices available for collimation. One of
the best is your eyepiece and Polaris. For this purpose it is best
that your telescope not be polar aligned, in fact point the mount
head due east or west.
Use your lowest power (largest number) eyepiece to acquire
Polaris, place it in the center of the eypepiece view. Now switch
to your next higher power eyepiece, while keeping the image
centered. The in-focus star image will have a bright innermost
point, a slightly fainter inner ring and a fainter still outer ring that
is hard to see (Fig.r-1). If it doesn't look like this, or you can't
reach focus then start with: take out your star diagonal and look
at the image slightly out of focus, this will allow you to gauge
the deflection. A typical off-collimation image will have a bright
spot off to one side when you bring the focus out (Fig.r-2).
The actual process is to slightly loosen the pair on the side the
deflection is, slacken the Allen head screws then tighten the
Phillip's head screws against them again. Check the star image
again after moving it into the centre of the eyepiece. If you find
your image getting worse, then go the other way, or slacken the
other two Allen screws a little. Once you have a round star
image you are set.
It helps to have a friend to help with the collimation.
Have your partner adjust the screws according to your
directions while you look in the eyepiece.
Replace the dust cap over the end of the telescope whenever it is not in use. This prevents dust from
settling on the mirror or lens surfaces. Do not clean the mirror or lens unless you are familiar with optical
surfaces. Clean the finderscope and eyepieces with special lens paper only. Eyepieces should be
handled with care, avoid touching optical surfaces.
Fig.r
Fig.r-1
Fig.r-2
22
Correctly aligned
Needs collimation