From: "Herb Kasler" 
To: "Jerry B. Hillman" , 
Reply-To: "Herb Kasler" 



Jerry,

Yous null zone is pretty mushy in the middle. I think you always have a bit
of that problem, but in your case it seems espercially bad. Looks to me
like one of two things is the case. Either your mirror is really flat in
the middle, i.e. close to spherical, in which case you'll get a giant null
zone in the middle, or you need a narrower slit and wire. I used a 50
micron slit and a human hair. Wider slits and wires gave noticably poorer
results. The hair was especially useful because it gave a very sharp line
due to refraction effects on the transmitted light. I also ended up doing a
hybrid test, where I used a knife edge for the inner zones and a wire for
the outer ones, overlapping them by three zones in the middle, where both
tests gave precise measurements. It did seem like the KE gave me a much
better reading on the inner zones. However, I didn't lose it as far out
from the middle as you seem to be. It was only my 50 and 80mm zones that
gave me ral trouble with the wire.


Later,

Herb.
>
> Hi all,
> I just posted a series of pics on my web site that shows my first attempt
at
> capturing wire test pics.
> http://www.convertabarn.com/wire_test.htm
>
> I need to learn how to do this.  I think it will be much easier to get
> accurate readings but I need a little guidance.
> Clear skies, Jerry
>
> BTW - The slit is .003" and the wire is .003"
>
>

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