There are two reasons to remove the focuser assembly:
If you are pulling the main mirror or,
If you are trying to correct image shift.
The main mirror in your C-8 slides up and down a central tube. The lubrication on this tube and the mirror hub can become unevenly distributed and this will cause image shift. By removing the focus assembly, you can grab the focus push rod and slide the mirror assembly up and down the tube to redistribute the lubricant.
To remove the focuser assembly:
Tilt the telescope UP so that the main mirror can not fall forward as you proceed. The mirror will not fall out of the scope, but it can be jarred by falling against the split-ring clip at the end of the tube!
Remove focuser knob by loosening the set screw.
You will find a brass sleeve under the focus knob Turn this sleeve until the focus screw extends out past the end of the sleeve. On this screw you will find a C-clip. Remove the clip with a pair of needle nose pliers.
Unscrew the brass focusing mechanism from the lead screw projecting from the rear of the telescope.
At this time you can grab the lead screw projecting from the rear of the telescope and move the mirror up and down the central tube. This will serve to re-distribute the lubrication and will help eliminate any mirror shift you might experience. Do this slowly since you do not wish to ram the mirror against the clip at the end of the tube! 5 or 6 slides from one limit of motion to the other should suffice to spread the lubrication.
Here is a picture of all the parts that go into the focuser assembly. Reassemble the focus mechanism in the reverse order of disassembly.
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