From: "Dwight K. Elvey" 
To: atm{at}shore.net
Reply-To: "Dwight K. Elvey" 


Hi Jack
 Actually it is just the other way around. It isn't
really critical that it be exactly square fore and aft. This can be easily
compensated for by slight tilt and placement of the secondary. Where as,
the side tilt will always end up with the primaries optical path not being
aligned with the OTA. Contrary to what others may tell you, you can bring
the telescope to optical alignment with all kinds of tilt of the focuser
assembly. Mechanical alignment may be another issue for vignetting. It is
important to separate mechanical and optical alignment. Their requirements
can be quite different.
 It is important that the focuser moves square to the eyepiece
but that is usually not adjustable. Dwight


>From: "Jack Schmidling" 
>
>It is understood that a focuser must be square fore and aft but is it
>necessary to square it radially or does the secondary rotation take care of
>that?  If yes and no, how does one go about doing this?
>
>js
>
>
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