[ATM] Re: ATM Digest, Vol 12, Issue 24

[artbianconi@blast.net]

I agree wholeheartedly Ken. ATM's are so smitten to seeing things 
measured in angstroms or wave fractions they think everything in 
the system has to be to similar tolerances.

And, as for the multi-point systems, I've shown them to 
machinists who build prototypes at Lucent (Bell Labs) and who are 
amongst the most skilled I know. They confirmed my suspicions 
that greater the number of fulcrums in a machanical cell, the 
greater the likelihood of assymetrical responses.

Art

> 
> --- artbianconi@blast.net wrote:
> 
> > I can assure you that if anything Solidworks has
> > become more powerful, not less as your statement 
> > erroneously suggests.
> > 
> 
> Hmmm... Seems I missed that one or we have a mix-up on
> identities...?
> 
> My statements are to illustrate that accuracy in
> computation is great - but only to a point!
> 
> That point is where the accuracy of computation
> exceeds the possibility of constructing the item given
> the technology, skills, and materials on hand. 
> 
> DESIGNING a mirror cell with PLOP (or a calculation
> tool 1000 times more powerful) is "KEWL" as the kids
> say. But... having a "PERFECT" mirror cell in the
> computer is a LOT DIFFERENT from what an ATM with hand
> tools is going to end up with in the scope.
> 
> Designing a cell to micron accuracy and building it to
> 1/16th inch accuracy will still give you a scope that
> performs better than observing conditions 95% of the
> time. Design the cell with PLOP but give me the answer
> in 1/100th of an inch (two decimal places) and I'll be
> happy. Any more accuracy is wasted expense and effort
> and certainly not worth worrying about.
> 
> If you want to design the cell to sub-nano whatever,
> please do but don't tell the beginner that his scope
> isn't going to be anything but a piece of crap unless
> it has gone through the PLOP or better optimization
> process. That just isn't true. Many scopes are made
> out of plywood and AstroTurf and they can produce
> images as good as (or better) than scopes with PLOP
> designed cells that are made and used in the real
> world.
> 
> BEGINNERS: If you want to use PLOP for a design tool,
> that's good as a starting point but don't get too hung
> up if you can't seem to make the attachment points
> exactly right or the pads are non-uniform in size,
> thickness etc. You can still end up with a usable
> scope even if you use plywood and AstroTurf cells in a
> cardboard tube. And... most of the time you couldn't
> tell the difference. I still remember the views
> provided by a 10 inch homemade mirror that was mounted
> on 3 nails driven through a piece of plywood for a
> cell. Wouldn't trade those memories for anything and
> will surely miss them when they fade away as a lot of
> other memories have done these days. Don't fret the
> small stuff, especially the stuff you can't control.
> Go build a scope and then another.
> 
> You can always make your next scope better.
> 
> Ken Hunter
> 
> 
> 
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