TS Optics TSLA User manual

1
Adjusting a Newtonian telescope
with an alignment laser
TSLA · LA1 · LA2

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Contents
WARNHINWEIS..............................................................................................2
Requirements .................................................................................................3
Checking/adjusting the laser..........................................................................3
· Checking the laser......................................................................................3
· Adjusting the laser ...........................................................................3
Secondary spider ...........................................................................................4
Secondary mirror offset..................................................................................4
What can be seen in the focuser?.................................................................. 5
Focuser...........................................................................................................5
Preparing the secondary adjustment .............................................................6
Excluding sources of error .............................................................................7
· Tilting of the laser in the focuser ................................................................7
· Clearance in the focuser ............................................................................7
· Checking the mechanical stability..............................................................7
Adjusting the secondary mirror ......................................................................8
Main mirror alignment ....................................................................................9
Do not look directly into the laser and the
direct reflection. Of course, the laser sour-
ce complies with the legal regulations and
does not exceed the permissible strength,
but it is still advisable to avoid direct
impingement of the beam on the eye as
much as possible.
You can recognize a direct reflection by
the fact that the laser causes a dazzling
effect.
Diffuse reflections which, for example,
reach the eye when looking at the laser
dot (on one of the mirrors or on the matte
screen) are absolutely harmless.
WARNING
TSLA LA1 LA2

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TSLA LA1 LA2
The TSLA, LA1 and LA2 adjustment lasers
have adjustment screws. Deviations in laser
alignment can thus be corrected quickly and
easily.
· Checking the laser
1. Place the tube of your Newtonian te-
lescope on a flat surface and secure it
against rolling away. Alternatively, you can
leave the telescope on the mount and tilt
the tube to horizontal.
2. Rotate the tube so that the eyepiece exten-
sion points vertically upwards.
3. Insert the laser into the focuser and tighten
the clamping screws (in the case of a ring
clamp) until there is no more play, but the
laser can still be rotated in the focuser. The
edge of the laser must rest on the focuser
without play all around.
4. Switch on the laser, look into the telescope
from the front and pay attention to the
laser dot, which is now visible on the main
mirror.
5. Rotate the laser in the OAZ. The laser dot
should barely move. However, if it de-
scribes a circle, the laser itself must be
adjusted.
· Adjusting the laser
The TSLA, LA1 and LA2 lasers have three ad-
justment screws with which the exit direction
of the laser beam can be set. If the screws
are covered on your laser model, carefully
remove the covers.
Now change the laser exit direction by turning
the screws so that the circle drawn by the
laser dot on the main mirror becomes smaller.
This usually requires that you approach the
correct position in small steps by loosening
and tightening the screws.
Make sure that all screws are tightened at the
end of the adjustment process.
The procedure described below assumes
that the telescope to be adjusted is mecha-
nically OK and roughly pre-adjusted, i.e. that,
for example, the position of the parts corres-
ponds to the nominal values/specifications.
Checking/adjusting the laser
Requirements
The adjustment screws are located 120 ° offset at the top of the housing.

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Secondary spider
The secondary spider usually only needs to
be checked after installation. Under certain
circumstances, such a check may be neces-
sary if bright stars on photographs taken with
the telescope do not show normal cross-
shaped, but deformed or double spikes.
For the first step, we assume that the primary
mirror is centered in the tube.
1. Check - e.g. with a metal ruler or a thread
stretched over the tube aperture - whether
the opposite struts are in line. If this is not
the case, the position of the secondary
holder in the tube is probably also incor-
rect.
2. Measure whether the secondary holder
is centered in the tube, i.e. whether the
distance between the holder and the tube
wall along the four struts of the spider is
identical. If this is not the case, you must
correct the distances by carefully loose-
ning or tightening the opposite screws by
the same amount.
Do this in small steps and always check all
four distances after each adjustment.
You may have to repeat the two steps several
times.
Secondary mirror offset
The primary mirror of the Newtonian tele-
scope forms the incident (parallel) light (a) into
a cone (b). In this cone sits the secondary
mirror (c), which deflects the light at a right
angle towards the focuser. The secondary
mirror should be as large as necessary (to
avoid losing light from the cone) but also as
small as possible (to avoid too much obstruc-
tion).
The size of the secondary mirror (small axis of
the ellipse) is oriented to the diameter of the
cone. If the center of the secondary mirror is
placed exactly on the optical axis (d), the re-
sult is that the front end (e) protrudes beyond
the light cone, while at the rear end (f) part of
the light does not hit the mirror.
By mounting the secondary mirror a little off
center on the holder and shifting the holder
a little towards the telescope aperture, both
problems are solved. This so-called offset is
already considered in complete telescopes
and does not have to (or cannot) be adjusted.
During the adjustment it is only to be consi-
dered that it can happen (in particular with
inexpensive telescopes) that the secondary
mirror is not centered in the focuser because
of the offset.
e
a
f
b
c
d

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opposing inner side of the tube
HS edge (reflection in the secondary mirror)
secondary mirror reflection in the main mirror
camera in OAZ view (reflection secondary-main-secondary)
secondary mirror spider (reflection via main and secondary)
inner focuser edge
secondary mirror edge
secondary mirror side surface
What can be seen in the focuser?
When the focuser is fully retracted and
the eye (or camera) is close to the focuser,
you will see the view below.
Offset
Focuser
The center axis of the focuser should be
aligned perpendicular to the optical axis. The
two axes should meet as closely as possible
at the correct point on the secondary.
The best way to check and adjust the focuser
alignment is with the secondary removed.
Usually this procedure is only done when the
telescope is being assembled. If the focuser
is to be changed,
it is a good idea
to adjust the
telescope be-
forehand so that
the new focuser
can be correctly
aligned with the
existing system.
If a new align-
ment is necessary
(without secondary mirror), the position of
the center of the focuser bore must first be
determined (position on the circumference of
the tube and distance from the front edge of
the tube), and then a mark must be made on
the opposite inner side of the tube.
For this purpose, with the OAZ removed, a
measuring tape can be placed around the
tube from one
edge of the OAZ
bore to the other
and the opposi-
te spot can be
determined. If the
mounted focuser
has a symmetrical
base plate, its
corners can serve
as reference
points.

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Preparing the secondary adjustment
After mounting the secondary, a rough
adjustment is necessary. Because the re-
flections of the main mirror can be irritating
when looking into the focuser (left), it is useful
to place a sheet of paper between the main
mirror and the secondary mirror. This way,
the secondary mirror stands out well from
the background (tube wall) as a matte white
surface without disturbing reflections (right).
The determined position can be transferred to
the front edge of the tube with a stop bracket
and the mark can be applied to the inside at
the correct distance from there.
A piece of masking tape and a suitable pen
are sufficient. It is useful to make the mark on
the outside as well, in order to know the cor-
rect position for any future adjustment work.
When the focuser is mounted, the adjustment
laser is inserted into it and the focuser is ad-
justed with the adjustment screws so that the
laser dot hits the reference mark.

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Excluding sources of error
· Tilting of the laser in the focuser
Insert the alignment laser into the focuser
and secure it carefully. Observe the laser
spot on the primary mirror. Loosen the clam-
ping screw and tighten it again. The laser
dot should not move or move very little and
should be in the same position after each
clamping. If this is not the case, your focuser
has a slightly too large inner diameter, which
can cause the laser to tilt. A strip of thin
adhesive tape on the barrel of the laser can
prevent tilting.
· Clearance in the focuser
To prevent clearance in the focuser from
affecting the adjustment, the focuser must
be fully retracted and locked in place.
· Checking the mechanical stability
Rotate the tube around the longitudinal axis
while observing the position of the laser
dot. Also bring the tube into an oblique or
vertical position. Rotate the tube around the
longitudinal axis while observing the position
of the laser dot. Also bring the tube into an
oblique or vertical position. The laser dot
must not change the position on the main
mirror.
Because small deviations are difficult to de-
tect, you should repeat the procedure with
the adjusted telescope. Then the laser dot is
within the center mark of the primary mirror.
The causes for a position-dependent devi-
ation can be an insufficiently tensioned se-
condary mount, one or more loose screws,
a too weakly designed spider or a deflecting
tube. The latter two fundamental problems
can lead to permanent errors during adjust-
ment.
Secondary mirror coarse adjustment
For coarse adjustment of the secondary,
a Concenter eyepiece is suitable, e.g. the
Concenter eyepiece 1.25” or the Concenter
eyepiece 2”. Insert the Concenter eyepie-
ce into the focuser and secure it in place.
Now look into
the focuser and
check the position
of the secondary.
Most likely, the
secondary will not
appear perfectly
round at first, nor
will it be centered
in the Concenter
eyepiece.
Rotate and move the secondary until the mir-
ror is positioned (after tightening the screws)
as shown in the picture on the right. If neces-
sary, you may need to loosen the adjustment
screws a little to move it towards the tele-
scope aperture.
If necessary move
the focuser a
little bit inward or
outward to match
the circles in the
center eyepiece to
the diameter of the
secondary mirror.
to the diameter of
the secondary.

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Adjusting the secondary mirror
The secondary mirror is adjusted exclusi-
vely with the three adjustment screws; the
centrally located fixing screw must not be
loosened again.
The aim is to align the secondary mirror to
the primary mirror in such a way that the laser
spot hits the primary mirror in the center.
Turn the adjustment screws only a little at first
to determine in which direction the laser spot
is shifted in each case. It is useful to alterna-
tely tighten one screw and loosen another to
achieve the desired movement. This prevents
excessive pressure on the secondary holder.
If one adjustment screw needs to be adjusted
to a greater amount, it is necessary to loo-
sen the other two screws minimally to avoid
distortion and/or damage to the secondary
mirror holder.
The laser dot must hit the center mark of the
primary mirror exactly. Once you have achie-
ved this, check that all adjustment screws are
tight.
After this step, check with the Concenter
eyepiece to make sure that the secondary
mirror still appears round and centered in it.
Especially if the secondary had to be adjus-
ted strongly, it may be necessary to repeat
the coarse and fine adjustment.
Before adjustment Correctly adjusted secondary mirror

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Main mirror alignment
Now the adjustment is completed.
Tip: Rotate the laser so that the aperture with
the matte screen faces the back end of the
telescope.
This will allow you to view the matte screen
while adjusting the primary mirror.
Usually there are three pairs of screws on the
main mirror cell. In the telescope shown on
the right, the adjustment screws have a star
grip, while the locking screws have a hexagon
socket head.
Loosen the locking screws a little and then
proceed as with the secondary mirror: first
determine the respective direction of move-
ment, then adjust. The laser dot visible on the
matte screen of the alignment laser must be
aligned with the central hole.
If this is the case, the locking screws must
be tightened carefully. Do not do this in one
pass, but tighten the screws one after the
other. Make sure that the laser dot does not
move anymore.
Before adjustment Correctly adjusted primary mirror