From: "Tom Krajci" 
To: "'hermit'" , 
Cc: 
Reply-To: "Tom Krajci" 


>From: klowther{at}cisnet.com

>> 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?

It CAN be the final arbiter.  It does not necessarily have to be.
Considering all the variables at play in outdoor star testing...and the
lousy weather many of us suffer under...you had better be real patient to
set it up right, and have mother nature cooperate too.

If you're gonna work that hard...make your indoor test setup well
understood and well controlled.  Then you can laugh at the weather, ignore
the issue of collimation, secondary mirror quality, etc.

All 20 of my mirrors were made without star testing.  They are all pretty
good mirrors.  Mel has star tested my 16 inch f/6 and I don't remember him
saying any bad things about it...but (as is typical in star testing)...the
couple times he's looked through the scope the seeing was not good enough
to really check the optics carefully.

>..."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.

The errors they allow to pass through their 'quality control' are errors
that can easily be caught in indoor testing.  They are keeping prices down
with a short time span of figuring spent on each optic.  Setting up an
outdoor star testing section of their production line would increase price,
and slow production.  Much of the buying public is not demanding that. 
Therefore we, as a collective set of consumers...let them get away with it.

You get the telescope manufacturing company you deserve.

>> 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.

I, and others, have previously mentioned that this 'gray scale' issue with
with focault testing is an inherent problem.  They eye is not a very good
'photometer'...especially when comparing apertures in a couder mask that
are some distance apart.  The eye is a much better judge of
*location* of shadows than *intensity* of shadows.  That begs the
question:

What simple, accurate optics tests, available to amateurs...use the
principle of measuring shadow location instead of shadow intensity?  The
answer to this question may improve your testing technique because you will
test using your eye's strength, not weakness.  (This is why I used the wire
test whenever possible...such as on my 16 inch f/6.)

(Note:  if you use a decent electronic camera setup you sidestep this
weakness of the eye...but I strongly urge you to read Suiter's article on
this approach.  You will avoid reinventing the wheel.)

Keep hammering away at the theory, and we'll improve the basis/foundation
of amateur optics testing.

Tom Krajci
Tashkent, Uzbekistan


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