From: "CSC" 
To: "Atm" 
Reply-To: "CSC" 


Yeah.  If you are inside of focus, showing maybe 10 rings or more, then the
brighter group of rings indicates a low zone or an area of shorter radius.
The placement of those brighter rings is equivalent to the position on the
mirror, assuming you've got a generally fairly close figure.  Typically the
edge shows a brighter ring, and any rings surrounding the shadow of an
obstruction (not relevant on the bench star test) will be brighter.

Use the Foucault or Ronchi to locate the zones more easily.


Colin
From: owner-atm{at}shore.net [mailto:owner-atm{at}shore.net]On Behalf Of
J-Engineering
Sent: Friday, March 14, 2003 1:23 PM To: atm{at}shore.net
Subject: ATM Testing a spheroid (again)



Hi All,

Several have suggested using a non-lasing laser diode in a star test for
testing a spheroid.

I have since set that up, and with the help of Suiter's Star Testing book,
I'm trying to figure out what the test is telling me.

Things look pretty good except I see a couple of adjacent  rings that are
brighter than the rest. Out of ten rings, they are the fourth and fifth
ring from the center as seen inside focus.  Does this observation tell me
where the problem is or just that there is one?  In other words, can the
star test tell you which non-edge zones need attention and what correction
to the surface is required?

--
Ray

--- BBBS/NT v4.00 MP