From: hermit 
To: Tom Krajci 
CC: atm{at}shore.net
Reply-To: hermit 


Tom Krajci wrote:
>
> From: hermit 
>
> >When possible, you should drop that part and do final figuring using
> the >star test any how.
>
> I fail to see the utility in taking your nearly-finished mirror out of
> the controlled testing environment of your basement/workshop/garage
> (where you are in control of all the variables in a small, manageable
> space)...and take it outside, where many variables are outside your
> control (weather, adding a secondary mirror...have you checked its
> surface figure?...atmospheric problems with real stars or across fields
> with artificial stars...collimation errors, etc., etc.)
>
> You call this an improvement?

I did say "When possible".

>
> I call it the abandonment of a controlled testing environment for a far
> more dubious testing environment.

It is that dubious testing environment" that the final product is used under.

>
> I recommend using the star test as a means to verify/certify/calibrate
> your indoor test results.  But you can only do that when you carefully
> control the variables in the great, wild outdoors.  (So if you're gonna
> sweat bullets to control parameters in the outdoors...move indoors where
> it's easier to control everything.  Work smarter, not harder.)

So you are saying that the star test IS the final
"verify/certify/calibrate" step?

>
> I'll ask an obvious question here:  how many major optics manufacturers
> (small and large volume) use star testing regularly as part of their
> figuring process?  Zambuto?  Pegasus?  And the list goes on and on.
> (Some do, but that's a minority.)

I'll answer a question with a question having looked through quite a few
commercial scopes.  "How many major optics manufactures do you wish
DID take the time to "verify/certify/calibrate" using the star
test.  Like Celestron and Meade maybe?  I think they would be considered
more major than Zambuto and Pegasus.

>
> Why do people have problems with indoor testing?  Simple.  They have not
> taken a methodical approach to their testing theory and technique.

Maybe they have trouble judging gray scales?  Personally, I've determined
that I would save more time if I star tested earlier in the process.  It
takes me about an hour before I am satisfied enough with my gray scale
guesses to put them into TEX.

>
> Why is Robo-Foucalt going through such long growing pains?  A lack of
> methodical approach to testing theory and technique.  (Lots of
> enthusiasm, but....)  Check out the article Suiter wrote a few years ago
> on foucalt testing with electronic cameras, software, etc.  Thank him
> profusely for laying down a solid theoretical basis...you only have to
> perfect your technique because Suiter did the first half of the job for
> you.
>
> How did I make 20 mirrors with reasonably good figures...without
> resorting to star testing at any phase of their work?  Simple.  I was
> methodical about testing theory and technique.
>
> Mirror testing is like computer programming - garbage in...garbage out.
>
> If you insist on mirror testing without a solid basis in theory and
> technique...you test mirrors at your own peril.
>
> You have been warned.
>

If you send your mirror off to be coated WITHOUT first star testing it, you
are placing your wallet in peril.  YOU HAVE BEEN WARNED!

Ken

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