Adjustment of Newtonian Telescopes with the
Laser-Colli™ by Baader Planetarium
Caution: LASER !
Never ever look directly into a laser beam! Protect your eyes!!
Store the Laser-Colli™ carefully so that it cannot be reached by
children or inexperienced adults. Consider that a heavily
Miss-aligned telescope will deflect the laser beam out of the tube
In an unpredictable direction possibly without you being aware of it.
Colli is the abbreviation for collimation.
In our context collimation is the alignment of the optical system so that the focal plane
of the telescope meets the focal plane of the eyepiece squarely.
Collimation is critical for good optical performance of your telescope.
Accurate collimation can be the difference in seeing or not seeing the Great Red Spot
and shadow transits of Jovian moons on Jupiter
Generally Newtonian telescopes are considered susceptible to a loss of image quality (collimation)
if, for instance, they are jarred or bumped, during transport by car etc. If this is a situation that you
have come across then a Laser-Colli™ will be a basic accessory to keep your telescope perform-
ing at it’s best. With a little preparation and a bit of practice your telescope will be correctly colli-
mated within a minute or two.
A Newtonian telescope can provide you with excellent images of astronomical objects – but only if
the primary mirror (concave parabolic mirror at the rear end of the tube) and the flat secondary
mirror (catching and deflecting the light out to the side of the tube and into your eyepiece) are cor-
rectly aligned with each other and additionally centered on their optical axes.
Let’s have a look again at the light path of a Newtonian telescope.
The incoming light travels first from left to right to the main mirror at the end of the tube,
is reflected there and travels right to left, to the secondary mirror, which in turn deflects
the light out of the tube and – via the eyepiece – into your eye.
