RE: [ATM] strange (collimation?) problem

["Koehler, Steve" <Steve_Koehler@securecomputing.com>]

Jan,

> BIG DIFFERENCE as compared to inside focus: secondary shadow not centered
> but very clearly offset to one side. When I centered the secondary shadow
> during the startest in the outside focus pattern, it became decentered
> inside focus and was then also clearly off collimation as seen in the
> cheshire.

I think this simply means that your optical axis is not parallel to the axis of
your OTA.  However, I would expect the secondary shadow to be off center on each
side of focus, but in opposite directions.

I have been puzzled by the instructions to do star collimation by centering the
secondary shadow.  It seems to me that this will not work very well with an
offset secondary, for example.  I have been meaning to run some simulations to
play around with this, but haven't gotten around to it, yet.

-- Steve Koehler
   steve_koehler@securecomputing.com

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