[ATM] Small Dob Question: Alignment features needed for accurate encoder GOTO's?

[Scott Carson <scottcarson@austin.rr.com>]

I'm building a relatively small 8 inch Dob (truss tube) to gain 
experience and am planning to add encoders.  Hoping to get some design 
advice / recommendations regarding mount "alignment" features to ensure 
accurate encoder GOTOs.

My GEM GOTO scope experience suggests that a GOTO Dob mount (any GOTO 
mount) must be mechanically "accurate" for successful GOTO's.  But my 
typical woodworking tolerances seem to be 1/32" versus maybe 0.005" for 
my typical metalworking projects.

So, I'm hoping to get some advice / recommendations regarding Dob mount 
"alignment" features that I should consider to ensure accurate encoder 
GOTO's. 

For example, are the altitude bearings typically accurate enough 
(perpendicular to the azimuth axis) with careful building (approx. 1/32" 
tolerance?) for successful encoder use?  Or should I consider adding 
adjustable altitude bearings so the altitude axis can be aligned 
perpendicular to the azimuth axis when setting up the Dob, ie, make the 
individual altitude bearings (teflon pad assemblies) that could be 
raised or lowered to accurately align the altitude axis to the azimuth 
axis.

Does the rocker box need to be "aligned" (adjustable?) on the ground 
board to achieve accurate alignment of the scope optical axis with the 
mount azimuth axis? 

If these "alignment" features are needed / recommended, do you have any 
suggested designs for adding these alignment feature(s)?

 From your experiences, do you have other "adjustment" features that I 
should consider to improve the final mount "pointing" accuracy when 
using encoders? 

Appreciate any advice and/or recommendations you can provide.

Scott

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