From: Guy Brandenburg 
To: "Jerry B. Hillman" 
CC:  atm{at}shore.net
Reply-To: Guy Brandenburg 


I doubt that a sonotube tube could be the source of that much flexing.
There has got to be something else that is moving - perhaps the laser
collimator is moving in the focuser? That would cause a large change. See
if it can wiggle. Also, have someone else look at your setup and give some
suggestions - it is hard to diagnose a problem like this from a distance
without photos and so on.

That is my 2 cents. Anybody else?

Guy Brandenburg

Jerry B. Hillman wrote:
> Hi all,
> When I tested my new telescope design for flexibility I put a laser
> collimator in the focuser, collimated it with the tube assembly horizontal,
> I then moved the tube to vertical while watching the red dot in the center
> of my mirror.  It didn't move enough to measure.  I then tried the same test
> with my 10" sonotube.  As I moved the tube towards vertical, the laser dot
> started moving down.  At vertical, the laser dot was a full 1 1/2" below
> center.  Moving the tube back to horizontal returns the red dot back to
> where it started. I know the focuser can't be moving. It is bolted down.
> The secondary holder is reinforced with a plywood ring next to the mounting
> points.  The mirror is secured and can't move, so that only leaves flexure
> of the tube. Is this something I can fix, or is it just due to using a
> cardboard tube. I am tempted to rebuild the 10" to match the
16.5" I just
> built.
> Also, couldn't this cause astigmatism? I have seen very slight astigmatism
> lately.
> Clear skies, Jerry
>
>
>
>

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