On Friday, June 12, 1998 12:03 PM, Jay Curtis wrote:

> I will have photos of the procedure tonight if anyone wants them,
> or would like to post them.
>
> JSC


I'll keep your e-mail address at hand for future reference and referrals.
By the way, how did the focuser upgrade work for you? How long
did it take? Do you like it? Was it as easy as I described? Please
post details on your methods and experiences as others may be
interested or need help as well.



>
> --
> Printed with 100% Recycled Electrons ...
> http://www.curtislumber.com ICQ 2947473
> http://www.curtislumber.com/llama ICQ 2456886
>
>
> -----Original Message-----
> Sent: Thursday June 11 1998 6:17 PM
> Subject: Re: [M]: RE: Improving SCT Focus Action
>
>
> In a message dated 98-06-11 11:05:58 EDT, you write:
>
> << Though the Meade SCT focus mechanism is quite adequate when
> adjusted properly, the focus mechanism feel may be improved with a
> few simple modifications and $3.54 plus tax for the necessary parts.
> For those that are mechanically challenged, this is NOT a complex
> procedure. Essentially, we are going to replace the nylon thrust
> washers with steel roller thrust bearings. Purchase the following
> parts at a bearing supply house (Berry Bearing or equivalent).
>
> (2) 1/2" ID roller thrust bearings (Torrington # NTA-815)
> (1) 1/2" ID 0.030" thrust washer (Torrington # TRA-815)
> >>
>
> I know this is a meade list but I also have a C-8 as well as a Meade as
> was
> wondering if this will work for a Celestron as well?


Here is a method I would use to adjust the focus action on a Celestron
SCT such as the 5" use for a guidescope on a Larger Meade SCT.
Celestron uses essentially the same focus mechanism on all their SCT's.
IMPORTANT! Check the final adjustment before proceeding as properly
aligning the Celestron focus assembly improves focus action considerably
and is likely all the adjustment you will need.

The Celestron SCT focuser uses a bearing retainer to house two sealed
ball bearings. A threaded brass barrel runs through both bearings. On
one end, a single set-screw holds the focus knob. On the other end is
a 1/2" wrench sized jam nut which is used to fix the inner races to each
other. There is no backlash adjustment. Generally, double ball bearings
whose races are fixed produce little to no backlash. The threaded barrel
pushes and pulls a non-floating focus rod (screwed into and stop nutted
to the focus arm).

To further loosen the action, you must remove the focus mechanism.
Loosen the focus knob set-screw and remove the focus knob. In the center
of the threaded brass barrel is the focus rod stop screw. Using a Phillips
screwdriver, remove this screw. There is likely a washer and aluminum
spacer under this screw. Next, remove the three bearing retainer screws
and slide the bearing retainer off. Finally, unscrew the focus mechanism
from the focus rod, removing it from the telescope.

Soak the bearings with the threaded brass barrel in solvent agitated by
an ultrasonic cleaner or other vibrating means. We want to dissolve the
heavy grease. We could remove the bearing jam nut and remove the
threaded barrel, but I believe heat would be required to soften any Locktite
used between the inner bearing races and the threaded brass barrel.
When the bearings turn freely, replace the grease with 20 weight oil
around the bearing shields while turning the bearings. Re-assemble in
reverse order. The lighter oil should free the focus knob action
considerably. Grease the focus rod and screw the focus mechanism
back on the focus rod.

Final adjustment is made by moving the bearings about under a loosened
bearing retainer to line them up with the fixed focus rod. Do this while
turning and moving the focus knob (moves the bearings under the bearing
retainer) while noting the smoothest focus knob action. The object is to
center the focus mechanism under the fixed focus rod. Finish by centering
the focus knob in the area of the finest focus action. Tighten all three of
the bearing retainer screws.


> Fred
>
>


--
Michael Hart
Husen Observatory

View index by [date] [author] [subject]
Previous message: Re: [M]: OT Iridium flares, Clark Williams
Next message: [M]: RE: PEC training with ST-7, Nigel Puttick
Next message in thread: [M]: RE: RE: Improving SCT Focus Action, Jay Curtis
Previous message in thread: RE: [M]: RE: Improving SCT Focus Action, Jay Curtis