From: Aplanatic{at}aol.com
To: atm{at}shore.net
Reply-To: Aplanatic{at}aol.com


Hi Tom,

I must (mostly) disagree.  See below.

> Let's see.  We don't have a good working Robo1...it does not compare
> accurately with known, well performing standards...so we'll make another
> unproven device against which to test it.  Huh?!?

As I see (and remember) it, James wished to test several possible sources
of error by building a new device.  One was related to the camera and the
other to the precision of the X-Y stage.  I personally would have first
measured and analyzed these sources of error to see if they were important
and worthy of improvement.  Each to his own method, as long as it's an
honest attempt.

> >In an effort to eliminate the hardware as the culprit, Robo2 has been
> >completed and tested against Charlie's mirror....
>
> >At this point, the obvious next step is to star test the optic, and see
>
> >what we see.
>
> Here you choose not to use a quantitative test method as a double check,
> but a qualitative one.  Again...Huh?!?

Yes, I also wonder if the star test will add any new knowledge to this
study. Personally, I've never been able to make quantitative assessments of
mirrors using it.

> >As it stands now, Robo doesn't agree with Couder Mask testing nor
> >interferometry done at RoC w/o nulling optics.
>
> It has stood this way for months.

Errr, hmmm.... James went to the trouble and expense of obtaining an
interferogram of the mirror.  This data has just recently arrived (on our
time scale of things.)  This is new knowledge, as I see it.  What I haven't
seen to date is a careful comparison between Robo, interferometry and
standard Foucault.

> I hope and pray mightily that you have not used Robo1 as the sole source
> of testing in order to fabricate any mirrors....unless of course, you
> clearly and unequivocally informed your end users that they are getting
> mirrors that are tested and certified (and I use those terms *very*
> loosely here) with an unproven method.  (Who would want such mirrors?)

James has honestly presented his Robo problem to this list.  I see no
reason to believe that he wouldn't share this with his fellow amateurs at
his ATM lab. Is it our business to ask?  Not in my book of etiquette.

> Yup, you are ready to take on Suiter.  I can see you are entering the
> battle of wits far less than half-armed.  I have no sympathy for you.
> The school of hard knocks is in session, and you are going for an
> advanced degree.

An ugly statement.  Are you bashing, or do you intend for this to have some
positive effect on James?  Or is your statement intended for consumption by
the rest of the list?  Or are you just steaming?  Hard for me to tell.

> Your signature line almost sounds like an excuse for sloppy,
> uncontrolled results where performance is not the final arbiter of
> technique.  But at least you are having fun...no?  ;-)

Yes, a careful and controlled experimental and theoretical environment is
always beneficial.  As I see it, James 1) discovered an unexpected problem
with his robotic Foucault test and 2) has been trying to find out why it
does this. To this end he has (perhaps in a less than perfectly controlled
manner) 1) asked for assistance, 2) made a new tester, 3) had an
independent lab measure a "standard", and 4) been very honest
about the results.  Not yet worthy of a graduate degree, perhaps, but not
bad, either.

> You are hereby filtered. 

You're free, Tom, to read or not read whatever you like.  No need, really,
to tell the rest of us.  I suppose "being filtered" is a
pronouncement of banishment, eh?

> Sadly, your enthusiasm and endless tinkering will, in my opinion, lead
> some folks down the proverbial garden path...in an undisciplined manner
> of acquiring techniques and skill.  It may inspire people to pursue
> their curiosity...but at the expense of little or no discipline.
>
> This gives the word "amateur" a bad connotation.

I think James' experimentation is a very positive aspect of being an
amateur. Hopefully after all this is over and digested we will know whether
a maskless Foucault test is valuable or not.  Or, even better, we will know
how to correctly use and interpret a maskless Foucault.  That would be a
very valuable contribution indeed.  Along the way, we may develop and
understand other wonderful things, like fringe analysis, Zernike
polynomials, and an appreciation that people are not all alike, and
contribute different and valuable things according to the bent of their
nature.

Dave Rowe

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