18
Manual: Baader Planetarium TriBand-SCT
looking in the direction of the Schmidt plate) pushes the main mirror towards the
Schmidt plate, a right turn pulls the mirror towards the tube back plate.
Now there must inevitably be some space between the outer diameter of the sky
baffle and the inner diameter of the sleeve; otherwise you could not move the sleeve.
This minimal difference in diameter (which is sometimes greater and sometimes smal-
ler due to temperature differences) is responsible for the so-called mirror shift. If you
turn the focus screw back and forth (left and right), the main mirror tilts minimally (due
to the play in the diameters of the guide sleeve and sky baffle) in its position relative to
the optical axis. During visual observation, this tilting is noticeable by a slight change
in the position of the object of observation in the field of view and is not too tragic.
The situation is different in photography: If the position of the telescope tube chan-
ges slowly in the course of the exposure time,
it can happen that the main mirror suddenly
changes its position and tilts slightly. This
results in a change of position of the object of
observation in the field of view.
The slight tilting of the main mirror can
easily be avoided if you "focus correctly". The
picture on the right is intended to illustrate
this. "Wrong focus" is when the focus position
is adjusted by turning the focus screw to the
right. The mirror is pulled back and the play
between the sky baffle and the guide sleeve
is at the bottom left. If the tube now slowly
moves to a more vertical position due to the
tracking, the mirror can suddenly slide back a
little under its own weight.
In the case of "correct focusing", tilting of
the mirror is impossible. If you turn the focus
screw to the left (counterclockwise), it pushes
the main mirror forward. The play between the sleeve and the sky baffle is now at the
bottom right. The mirror mount is practically clamped onto the Sky Baffle with the
guide sleeve. This prevents the mirror from tilting.
Attaching Accessories
Caution:
For mounting accessories, only the three pairs of pan head screws
1
,
2
and
3
in the illustration on page 19 may be loosened on the rear tube cell, but
not the other countersunk screws. For mounting accessories, you may need slightly
longer screws (8/32 UNC, 1/2 inch). Do not use screws that are too long, as they may
damage the main mirror. There are one or two screws
4
on the front tube cell which
are used to attach an accessory bar (together with the pair of screws
2
). We offer
matching screws under order number
# 889001
if no matching screws are included
with your accessories.
Play
Play
Push
Pull
Focusing
clockwise
Focusing
counter-
clockwise
Mirror can
move
Mirror is
locked
