Meade LXD 75 Instruction Manual page 41

Tip:
A useful tool for making
collimation easier is to make
a hole in the plastic cap that
comes with the eyepiece to
protect it during shipping.
Use a drill to make a 1/8"
hole in the center of the cap
and place it over the eye-
piece holder for use during
the collimation procedure.
Fig. 31b: The four collimation screws
on the diagonal mirror housing.
knurled knob
thumb screw
Fig. 31c: The six collimation screws
on the rear of the primary mirror cell.
b c d e
Fig. 31a: The view you will see while collimating a Schmidt-Newtonian telescope.
shipment of your telescope. It is only necessary for you to confirm that the telescope
has not been badly jarred out of collimation, and to perform the final fine-tuning of Step
4, below.
Fig. 31a shows a correctly collimated Schmidt-Newtonian telescope, as it appears
when viewed through the focuser with the eyepiece removed.
To check and, if necessary, set the optical collimation, follow these steps.
1. Observe through the focuser and orient your body so that the telescope's primary
mirror is to your right, and the correcting plate end of the telescope tube is to your left.
The diagonal mirror will appear centered as shown (2, Fig. 31a). If the diagonal
appears off center, then adjust the 4 collimation screws on the plastic diagonal mirror
housing.
2. If the reflection of the primary mirror (3, Fig. 31a) is not centered on the surface of
the diagonal mirror, adjust the 4 collimation screws on the plastic diagonal mirror
housing to center the reflection.
As described above, the 4 collimation screws (Fig. 31b) on the plastic diagonal mirror
housing are used for two different adjustments during the collimation procedure.
Important Note: Do not force the 4 screws past their normal travel, and
do not rotate any screw or screws more than 2 full turns in a counter-
clockwise direction (i.e., not more than 2 full turns in their "loosening"
direction), or else the diagonal mirror may become loosened from its
support. Note that the diagonal mirror collimation adjustments are very
sensitive: generally turning a collimation screw 1/2-turn will have a dra-
matic effect on collimation.
3. If the reflection of the diagonal mirror is not centered within the reflection of the pri-
mary mirror, adjust the 3 collimation screws located on the rear of the primary mirror
cell.
Note: There are 6 screws (Fig. 31c) on the primary mirror cell. The 3
knurled knobs are the collimation screws, and the 3 smaller thumb screws
are locking screws. The locking screws must be loosened slightly in order
to adjust the collimation screws.
Proceed by "trial and error" until you develop a feel for which collimation screw to turn
in order to change the image in any given way.
b
Focuser drawtube
c
Diagonal mirror
d
Reflection of primary
mirror
e
Reflection of secondary
mirror (darkened due to
back lighting)
f
Primary mirror clips
g
Reflection of observer's eye
f g
4 1