Re: Dobsonian mount - azimuth bearing question

"Starboard" wrote:

> For the most part, the bearings are smooth. But, when using higher
> powers and tracking an object overhead, the azimuth bearing seems
> slightly jerky. It's smooth while you are slewing, but, if all you want
> to do is just nudge it a tad, you must first overcome the friction
> between the nylon (or Teflon, not sure what it is) pads and the black
> Formica underside of the upper platform mount.
>

Errol, You are fighting leverage (and possibly other things - but first
let's look at leverage). When a Dob. Style Scope is vertical, rotation
becomes more difficult because you no longer have a lever working in your
favor (hence "Dob's Hole"). Simple no cost solution (given it works well at
all other times) is to just wait until the object moves to a lower position.
As to lubrication options try to avoid ANYTHING that could collect and
store dust and/or "grit" as they will slowly both grind away and in doing so
embed crud into the bearings that will over time make the whole situation
worse!.
A simple test to see if your bearings are working properly is to set your
Scope at say 70 of 80 degrees above horizontal and pull it at a 45 degree
angle. If the force required is equal in both vertical and horizontal you
are better off living with it than making one better than the other.


Crazy Ed

.

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