RE: ATM Speaking of Dob Bearings

[Adam Perkins <scopeguru@yahoo.com>]

"Bertapelle, Ken" wrote:
>The
> situation you
> want to achieve is one where the scope responds to a
> very light
> touch to move it, but then stays put, with no
> backlash, when to
> take your hand away.


Hi,
I'd argue that much more important that low overall friction in dob
bearings is not as important as having the STARTING friction be very
low.

My small dob was purposely designed to be a little bit stiff (I used
large brearings).  When kept within reason, a stiff set of bearings
does indeed help with balance problems, I don't use any counter
weights.  The thing that absolutely cannot be tolerated is a bearing
that sticks as it BEGINS MOVING.  

Ebony Star and Teflon have the desireable trait of taking almost the
same amount of force to BEGIN sliding across each other as it takes to
CONTINUE sliding.  Many otherwise "Low Friction" surfaces have a higher
starting friction, forcing you to apply so much pressure that when your
bearing does begin to move, you have too much force applied, and you
overshoot.

Kriege and Berry's books also covers this.

Clear Skies

Adam Perkins
Covington, Louisiana

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