The laser does not reach the precision need for astronomical use, but it is useful for the first rough
approximation after a major overhaul of the telescope. We use the laser in the factory only once,
when the telescope is assembled the first time.
6.4A) Primary mirror tip-tilt regulation: laser
VERY IMPORTANT: If you have just reassembled your telescope (typically after a re-coating of
the mirrors) then read this section.
Otherwise, jump to section 6.4B, “Primary mirror tip-tilt
regulation: star”.
The procedure is quite easy:
1. Install the conical flange how you have done with the Takahashi collimator, and insert the
laser into the flange. Lock it in place.
2. Turn on the laser. If the laser spot hits
exactly
the middle of the circles on the secondary
mirror, skip the next step and jump to point 4.
3.
If the laser does not hit the middle of the "target" on the secondary mirror, tilt
the whole
flange, with the laser inside
, using the push-pull screws that lock the flange to the
backplate. That's the reason why there are 6 tethered holes in the flange, even if only three
screw lock it to the backplate. This move may "sound strange", but it is in practice
impossible to build a "perfect" laser (i.e. with the laser beam
exactly
on the mechanical
axis). On the other hand, what you
really
need is the center of the beam in the middle of
the secondary mirror. So the idea to tilt the flange with the laser inside has a lot of sense!
4.
When the laser hits exactly in the middle of the
"target" on the secondary mirror, point the
scope to a wall or a big piece of cardboard,
perpendicular to the optical axis
. The
distance between the scope and the wall is not
relevant. Anything between 0.5 and 5 m will be
ok. What is important is that you see the laser
pattern projected on the wall/cardboard.
5. You will see the pattern created by the laser
(circles or squares, depending on the model of
your laser) and the shadow of the secondary
mirror. If a “two stage” light shield is installed,
you will see
two
shadows.
A telescope with a “two-stage” light shield before the tip-tilt
regulation of the primary mirror. Here a “square” pattern laser is in
The same telescope after the tip-tilt regulation of the primary
mirror. Please note that the shadow of the “second stage” light
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