Will this mod improve the focus control of a new LX200 12" and 8" scope.
I've heard the 12" have a slightly different focus control with a spring
inside the tube.

Mike

-----Original Message-----
Sent: Tuesday, July 31, 2001 4:43 PM
Subject: [M]: RE: Focus bearing modification


Hi Philip.

Thank you again for your comments. For a relatively simple product,
it's hard to believe that we had a full man-month of engineering invested
in it before we released it. There were many many fine details that
needed to be addressed, and based upon inputs such as yours we
continue to improve this product.

The long arm Allen wrenches are on order and will be substituted in
the kits later this week when received. And as soon as you and I
(working together) identified the source of your problem the kit
instructions were revised to more strongly warn against damaging
the brass focuser insert. We also explained in detail just why it's
so important not to leave pliers marks on the brass focuser body.

Although we'd sold a good number of the EZ Focus Kits you
were the first person and only person that I know of to encounter
this problem. With 4 pages of detailed instructions you'd think
we'd had covered everything.

Details on this kit are available at:
http://www.peterson-web.com/SkyDiv/ez_focus_kit.htm

Regards,

Pete Peterson


-----Original Message-----
Philip Peake
Sent: Tuesday, July 31, 2001 11:51 AM
Subject: [M]: Focus bearing modification

Some comments which may be of interest to people thinking of making this
modification:

I decided to try out this modification mainly hoping it would remove some
of the backlash in the focus control.

Not being able to find a local distributor of the thrust bearings I decided
to take the easy way out and order the kit.

I have to say that ordering was easy, and I soon received my kit, which
contains everything promised including some quite clear documentation on
how to perform the modification.

The only part I have any issue with is the warning about using pliers and
paper or cloth to hold the brass body of the focusser while unscrewing it
from the aluminum knob.

The warning really isn't strong enough !

The brass used is very soft. Even holding the brass body with some padding,
it is all too easy to distort it at the edges, particularly because the end
being held is thin, and difficult to grip.

Mine ended up with some small dents in the edge which were enough to raise
bumps on the top and bottom of the flange against which the thrust bearing
runs.

When I assembled the bearings and tried turning it, it all moved easily
but there were definate bumps to be felt while turning - this was the
small, really difficult to see bumps raised on the brass flange.

It took some time with a fine stone to remove these bumps.

Once that was done the focusser assembly turned rather smoothly and easily
compared to its original state.

After re-assembly, I was a little dissapointed. The movement was easier
but now there was some "gritty" feel when focussing ... pulling the focusser
assembly out again, it turned smoothly. Pushing the mirror assembly back and
forth with the retaining bolt revealed a definate "gritty" feeling to that
movement.

I swept it back and forth a few times, and it got better, but I still won't
call it really smooth.

The tension on the thrust bearings also makes a big difference, to little
tension and the mechanism is sloppy, too much tension and the bearings
begin to feel "gritty".

After some thought I decided to see if I could make the focusser move even
more
smoothly by experimenting with different grease.

Eventually, I found that I got best results by using a PTFE grease intended
for lubricating guns (Tetra Gun Grease). This results in a really silky
smooth focusser.

I also removed the focus screw, cleaned off the existing grease on that
and used the Tetra gun grease to lubricat that thread, as well as the hole
and bar on the mirror assembly to which it attaches.

This seems much smoother than using the Meade recommended grease.
I can still feel some 'grittyness" as the mirror moves back and forth, but
that is definately not due to the focusser now.

This grease is not cheap, but I do suggest trying it out with this
modification. My results are certainly better.

Also, if there is *any* feeling of bumps or grittyness in the focus
assembly when not fitted to the telescope. Take a long hard look at the
brass flange and see if there are any small areas of distortion caused
when dissasembling (hopefully, most people's focussers will come appart
somewhat more easily than mine did !).

One final remark on the kit: the allen key provided is too short to make
removing the retaining screws easy. I ended up using one of my own, about
an inch longer ... much easier.

Philip

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