Re: [ATM] squaring truss tubes and collimation

["Mel Bartels" <mbartels@bbastrodesigns.com>]

>    "As long as the focuser operates along the secondary optical axis"
>    Exactly.

A flat diagonal has no optical axis (it may have an arbitrarily defined 
geometric center).  Therefore, statements like 'squaring on', and focuser at 
'90 deg', have no reality.

The single and only condition that must be met is that the imaging axis (the 
camera, the eyepiece) be coincident with the primary mirror optical axis. 
(The word 'collimation' is inappropriate as it means parallel to, or 
aligned: both insufficient as viewed from the condition of coincidence.)

Rotating cage adds the extra mechanical complication in that the cage's axis 
of rotation must be coincident with the primary mirror optical axis.  But 
the secondary and focuser positions, as long as the single and only 
condition that I just stated is satisfied, are not constrained.

Mel Bartels 

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