Re: [ATM] Hill or hole?

[Dale Eason <atmpob@yahoo.com>]

I think it is obvious.  Do a proper foucault test with
measurments.  It will tell right away which way it is.
 In this case you don't have to be very accurate
either probably only need a three zone mask.

How were you planning to control your figuring?

Dale Eason


--- David Bevel <dhcb@bellsouth.net> wrote:

> Hi All,
> 
> 
> 
> I have been wondering about an issue I have
> concerning Foucault images for a
> 
> while now and thought I would see what you folks
> have to say about my 
> conundrum.
> 
> 
> 
> I have a mirror that has a problem. I have either a
> hill or a hole but not 
> sure which.
> 
> Looking at images I have seen on various sights that
> provide examples of a 
> hole and a hill
> 
> and having reviewed the remarks that accompanied the
> images I wonder how one 
> can tell
> 
> what you have unless you know for a fact what either
> condition looks like in 
> reference to
> 
> which direction your knife edge comes from  as it
> approaches the mirror. I 
> would think your
> 
> image of the mirror produced with a knife edge that
> moves left to right 
> would be a mirror of
> 
> one  produced with a rig that brought the knife edge
> in from right to left. 
> In essence a mirror
> 
> defect could appear as a hole to one test rig and a
> hill to the other.
> 
> So lets say I have image taken with a left to right
> moving mirror and my 
> image shows a deep
> 
> shadow on the left side of the hole/hill and a
> brighter area on the right 
> while the rest of the
> 
> mirror outside the hill/hole is bright on the left
> and darker on the right. 
> What have I got?
> 
> I also, hope I don't have any prints of the image
> upside down.;) Now for you 
> highly intelligent
> 
> deep thinkers this may be blatantly obvious but to a
> fellow who gets 
> headaches doing a simple
> 
> tax return uh, No!
> 
> 
> 
> Thanks in advance,
> 
> 
> 
> Dave Bevel 
> 
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> 



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