Celestron StarSense Explorer 12" f/4.9 Dobsonian Telescope - Manual (Page 15)

ENGLISH I 15
b. If one set screw becomes too tight or too loose, make
adjustments to the other set screws to compensate.
2. Continue adjusting the set screws until the primary mirror
appears centered within the secondary mirror (Figure
19). When you are fi nished, make sure all three of the set
screws are snug.
Edge of
secondary
mirror
Refl ection of
primary mirror
Refl ection of
secondary mirror
Figure 19: Continue making tilt adjustments to the secondary mirror until
the primary mirror refl ection is centered as shown in the drawing above.
3. Next, adjust the tilt of the primary mirror until the refl ection
of the secondary mirror is centered within the refl ection of
the primary mirror.
For the 8” Dobsonian, use the 2.5mm hex key and Phillips
head screwdriver to tilt the primary mirror. There are three pairs
of collimation screws. Each pair works together to adjust the
tilt.
a. Adjust one pair of screws at a time. Start by loosening
one of the screws in the pair and tightening the other
(Figure 20).
Figure 20: For the 8” Dob, there are three sets of push-pull screws in the
mirror cell that adjust the tilt of the primary mirror. Loosen one screw in the
pair and tighten the other to adjust the tilt.
b. If the mirror tilts opposite the desired direction, loosen
the screw that you previously tightened, and tighten
the other screw in the pair.
c. Once you have adjusted one pair of screws as much as
you can, move onto another pair of screws.
d. Continue adjusting until the refl ection of the secondary
mirror is centered within the refl ection of the primary
mirror. When you are fi nished, the view through the
collimation cap should look like Figure 16.