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Why aren’t Celestron C6 focusers as good as their older C’s?

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Why aren’t Celestron C6 focusers as good as their older C’s?


Anyone that has used an older C5, knows that the focusers were….special. The C6’s, while seemingly universally excellent optically, have a fairly stiff and inconsistent focus feel.


Having just found myself the coincidental owner of both scopes, I set about to find out why.


On the older C5’s, the focus rod is supported on 2 stacked ball bearing races and provided that the retainer ring is not overtightened or decentered, the focuser could just be rolled with a finger. Super light and easy – sublime.


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The C6 focuser mechanism has a rubber focuser knob that is pushed over the focus shaft extension and extends into the bore of the trim ring. There is no adjustment possible on the knob itself to move it in or out.(ie: no set screw) and the more the retainer ring is tightened, the more interference there is between the molded rubber focus knob and the retainer ring. It can be frustratingly stiff.


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The answer. Get a razor blade and trim the rubber cladding back from the retainer ring by about 1/8”. Just enough to let the cladding clear the retainer ring.  The rubber knob can be ‘worked’ off the focus shaft extension so cutting a neat 1/8” ring off the end is easy. Just push it back on and voila! – you now have a nice, light focusing action.


You could just work the rubber cladding off by 1/8” as an alternate, but I’d want as much of the cladding in contact with the focus shaft extension as possible.


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Incidentally, while you have the rubber knob off, you will notice that the C6 does indeed use a bearing race for its focus shaft. Why engineering thought it would be good idea to degrade this nice smooth action by introducing rubber on metal friction….who knows?


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In any case, having done this, your C6 focuser will now be as light and easy as a C5. It does not affect the focus in any way but positively.


The feel is great, and it doesn’t introduce any backlash or play.


And you can’t tell any mods have been made after you push the rubber cladding back on.


So, Gentlemen and Gentleladies – get your knives out. (just not for me please)


  • Zackaryk1, mclewis1, Snickersnee and 20 others like this


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