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On Left: Clear, translucent Reference
plane with etched cross-marks
Most laser collimating devices use a sim-
ple opaque piece of plate glass to act as
indicator for the returning laser beam.
Many small suppliers just scratch the
glass by using sand paper in order to get
a cheap opaque reference plane.
Our Clear Reference plane is etched (not
printed!) with hundreds of tiny crossmarks
so that the returning beam lights up in the
ever so tiny grooves of each individual
cross that is being touched by the laser
light.
Not only does this produce a much more
concentrated dot, the main benefit is the
fact that our reference plane is not
opaque!
Whenever your optical system is just
slightly misaligned, it is no problem to im-
mediately recognize the reflected laser
beam on the glass reference plate.
But what happens when you don’t see any reflected dot at the reference plate due to a moderate
de-collimation of your optics?
In the case of an opaque reference plate the returned laser beam will not be visible at all and you
will be unable to view the returned beam in the focus tube.
The clear reference plane of the Laser-Colli™ will allow viewing down the focuser tube through
the etched plate, and in most cases it will be possible to glimpse a reddish glow were the laser
beam grazes the focusing tube internally.
That is the reason for placing the glass reference plate as near as possible towards the focuser
and to design the body of the Laser-Colli™ in a way that makes it easy to look almost straight into
the focus tube from behind.
Step-by-step procedure to collimate your Newtonian telescope
1. Mark the geometrical center of your primary mirror.
Remember the important requirement that the laser beam touches the primary mirror centrally –
exactly in the middle of your center mark.
If the secondary mirror is tilted only slightly out of its necessary 45° angle against the ocular holder,
the laser beam will not be reflected down towards the center of the main mirror.
Therefore you should prepare your system for the first (and all following) collimation(s) by marking
the geometrical center of the main mirror.
This requires, in Newtonian telescopes with a closed tube, removing the main mirror cell from the
tube. The removal results in the need for re-collimation afterwards of course, but this is done with
the Laser-Colli™ in no time.