Re: [ATM] Mirror Cells - Springs vs. Push/Pull

[Daniel Fundo <fundo@bellsouth.net>]

<<   Also there must be some sort of allowance for the angle change or
tip-tilt of the bolt during collimation. That is what the  flexure
machined  into the bolt if for. To allow for tip-tilt but be axially 
and radially rigid.  >>

We have been down this road before!  How much adjustment do you need to
align the mirror?  The short answer is: enough to accommodate the
inaccuracies you build into the OTA.  I checked the spacing between the
mirror cell and the back plate of my 12.5 inch the last time we had this
discussion.  I had to pull out the calipers to measure it...0.011 inch
difference around the circumference, IIRC.  If this old TI calculator is
correct, that's an angle of 4.2 minutes across the 9 inch spacing on the
alignment sets.

Now.........I have a lot of experience building things.  I tend to be a
perfectionist when I work on my own stuff.  I measure twice and cut
once.  I don't think I can make a hole tight enough, without having to
pound the bolt through, that wouldn't accept that much "slop"!!

If you can't build an OTA from the materials we commonly use around
here, namely wood, aluminum, plastic,  using common workshop hand and
power tools, and keep everything within 1/8 inch of parallel and square,
then you're in the wrong hobby.

*****-----
Dan F.
Former Secretary/MAS
Memphis, TN
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