Re: [ATM] Tester question

[Ben McIlwain <cydeweys@gmail.com>]

Francis J. O'Reilly wrote:
> Guy,
> 
> I am very impressed with your combination tester, perhaps the most
> interesting part was the optical alignment function, that is the
> light which is reflected back to the tester light source to assure
> that the apparatus is properly aligned. My weakest area in testing
> has always been setting up the tester. Your idea makes the alignment
> a sure hit every time.
> 
> To that end I am making a tester that is similar to yours for my
> home. Can you advise me as to the type of light source that you use
> for the alignment light? I'd also like to know where it was purchased
> if you remember.
> 
> Thank you and best regards to you and yours for a blessed holiday
> season.

Well, I've used the Ronchi tester at the workshop enough to know how it
works, so here you go.  The alignment light is nothing more than an
off-the-shelf red laser pointer, which you should be able to get easily
for less than $10 at many stores.  We use a clothes pin on the power
button to keep it turned on.

The laser pointer fits into an appropriate diameter hole cut into the
end of a roughly ruler-proportioned piece of wood.  The other end of the
wood is secured with a rotating mount, so the laser pointer can be swung
into position to point through the top opening in the diffraction
grating for alignment, then rotated out of the way so you can look
through the grating for the Ronchi test itself.  It's a nice and simple
setup that works very well.
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