DIY Focuser bearing kit for 8"LX90ACF

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Piet Le Roux South Africa
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DIY Focuser bearing kit for 8"LX90ACF


Post by Piet Le Roux »

I have been thinking of doing this mod on my LX90 for some time but the focuser bearing kit for LX90/LX200 scopes are a bit expensive. The original recommended bearings for this modification are 2 Torrington NTA-815 1/2" thrust bearings and a TRA-815 thrust washer. On Amazon I found this bearing in sets of 3 (3 bearings and 6 washers) under Uxcell TC815 for less than 10$ and ordered some for doing my mod. With my LX90 model I had a bit of work to do because the bearing and washer on the focuser knob side did not "ride" on the 0.5" part of the brass bushing so I had to remove about 3mm of the black aluminium retainer. I did this by sanding it on black silicon carbide waterproof paper on a piece of level marble stone. But it is difficult not to go skew by hand so when you get close, insert the bearings without lubricant with a fair amount of tension. Work the focuser outside the scope until it starts to seat, the markings will indicate where you have to apply extra pressure when sanding, for final sanding I used 400 grid. Work the focuser with lubricant and extra tension until the aluminium, that you sanded, has a mirror like Finnish where it makes contact with the bearing, then remove and clean everything to remove bits of metal and re-lubricate. Normally you would tension the focuser by turning the focuser clockwise till it stops at the end of its travel, then with set-screws released continue to turn the focus knob clockwise until it feels snug (this will remove all of the backlash in the focuser mechanism). With the set-screws still released, turn the focus knob counter-clockwise about 1/16th of a turn but with the bearing mod you leave it snug with a bit of tension. The result is that focusing feels buttery smooth with no play.

Here are information and illustrations : ... cuser.html ... ermod.html
Main Equipment : Tele Vue 27mm Panoptic, 7&13mm Nagler, Big Barlow : 8" Meade LX90ACF with Meade 2.0" Enhanced Diagonal : Camera Fuji XT100
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