From: J-Engineering 
To: CSC 
CC: Atm 
Reply-To: J-Engineering 


Hi All,

The improvements to my "focusser mounted" Foucault tester and
approach include: 1)  Cleaning up the knife edges using CeO and a piece of
flat glass. 2)  Adding a "sticky backed" refrigerator magnet to
the slit holder surface 3)  Using a 30 to 50 micron slit and using a 10x
loupe to check the slit image in the
return
4)  Obtaining brighter LED's from Digi-Key.com Nice selection with outputs of 7200
millicandela for yellow, 2400 millicandela for green. 5)  Added a digital
caliper to the draw tube to measure position 6)  Made sure the mirror was
as clean as I could get it in a reasonable amount of
time.

For this 8" spherical mirror, and using a 3 zone mask,  the averaged
(8 sets, sd=0.07)
knife edge positions in mm are:
0.0000 (inner)
0.108
-0.070 (outer)

Putting these numbers into Sixtests results in a plot of 12 units maximum above the
y=0 reference line, and 6 units below.

Does this mean this is a 1/(12/560) or 1/46 wave on the surface, or 1/23 wave on the
wavefront?  What I'm looking for is a check on the interpretation of the numbers, not
so much a judgment on defects under the 3 zone Couder mask.



CSC wrote:

>         I recommend the knife edge test, Snip.....

--- BBBS/NT v4.00 MP