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• Note the side of the focuser your eye is on. If you are looking down the focuser at
the bottom or 6 O'clock, and then on the Outer Edge of that Central Black
Doughnut you will see a VERY THIN dark ring at 12 O'clock to that Black
Doughnut. This is a reflection from the secondary baffle.
• Now as you move your eye around the focuser, being sure to keep your eye at the
edge of the focuser looking straight down the focus tube not in the center, moving
from 6 o'clock to 7-8-9 etc the space between the outer edge of the Central Black
Doughnut will remain the same.
• As you learn what to look for here, you can move the focus tube OUT to make the
adjustment even more critical, but harder to see when learning.
If the thin ring is not evenly spaced from that central black doughnut, then you will
need to adjust both Push/Pull screws at the back of the telescope until it is. These are the
same set of screws on the far outside of the optical tube on the rear that you used for the
Star Test procedure above. Then use the above Star Test method for final critical
collimation.
Secondary Mirror
If you have taken out or need to take out the Secondary, remember not to lose any of
the washers between the mirror holder and the center of the spider vanes. When
retightening the set screw remember to first tighten all 3 "pull" Phillips screws equally
(one turn each until holder is stable). Then tighten the 3 "push" set screws equally until
they are all just snug.
• Point the telescope at an evenly illuminated wall being sure it is well away from
the sun. This point should not be in the path of the sun for the duration of this
process.
• Rack the focuser all the way in and insert the Centering Eyepiece. You will see a
dark ring in the center of the view, if it is off centered, you will need to center it
using the collimating adjustments on the secondary mirror holder.
• Once you believe this is close or perfect, then extend the focuser as you are
watching. The dark ring outside the primary should be equal in all directions, and
then as you adjust the focuser back, the dark ring will disappear all at once.
• You are seeing the very edge of the primary mirror complete the field. If you do
not see this, adjust the secondary until this happens.
• To adjust, be sure to loosen one push screw before you tighten any others as the
secondary mirror can be over-tightened and cause distortion of this flat optical
plane.
Adjusting the Focuser
Remove the Secondary Mirror making sure not to lose any washers and mark the
orientation. Do not remove the spider assembly; the secondary will come out if you
carefully slide it between the spiders.
• Rack the focuser all the way out, if you have any extensions you will want to use
them or the Star Diagonal Flip Mirror, with the mirror out of the optical path.
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