ATM accuracy of centering primary mirro

[PFAFF2@delphi.com]

>
> I have centered my primary as good as possible. But I do not know if it is 
> exactly centered. It is possible that the mirror is placed 1 millimeter or so 
> out of center. What is the tolerance? I have a 12 inch f/6 newtonian; tube 
> inside diameter 15.2 inch.
> 
> Jan
> 
 
Accurate tube centering is no great importance unless you have a
rotating tube set up. And even then if you get the optical axis
parallel to the tube it will still work. It is more important
to get the focuser squared on to the optical axis. Use a site tube
to do this. A better way now is use a laser in the focuser.

Heck  most tubes are not even round to within .050"

Let see in your case 15.2" tube minus 12.5" mirror = 2.7"
divide by 2 = 1.35" mirror to tube wall clearence.
Now we could off center mirror by as much.35" and still have 1.00" clearence.
1" is still good mirror to wall clearence for tube currents.
( ok flame me on the tube current clearence but I just making a point:-))

Regards
Bob Pfaff