--- In VacuumX@..., "Ron" <ron_white@s...> wrote:
Hi gang
Hi to Ken / James / Les
Congrats to Ken
I just found your group I haven't started to put together a vacuum
system yet but it is on my list and I'm collecting info.
I am an ATM guy I have ground polished and destroyed 2 mirrors a
12"
and a 16" I purchased both at the same time from ASM they were
supposed to be ceramic low expansion and all of that and the price
was great. Both were laminated from ?" thick pieces of black
glass.
the 12 " I ground ok but it was astigmatic so I reground it and was
polishing on a machine, the power went out in my shop and the
mirror
stuck to the tool and when the power came back on $$%^&*( oh
well.
When I saw how the glass was laminated together I know why it kept
bending on me. When I ground the 16 "F4 I didn't have any problem
with astigmatism but I ground thru the first layer of ?" glass
there
were a lot of voids in this blank from not being fused properly so
it
was an ugly mirror. I had a lot of problems with scratches I think
from the pieces of glass chipping up from the void areas. When I
finally got the scratches under control I couldn't repair a bad
zone
at the transition area between the laminations it was as if the
glass
bond area had stress or was harder than the surrounding glass.
Because the glass was black I couldn't check it with polarized light
The best I got to was 1/3 PV. Would have been 1/8 PV if I blacked
out a big doughnut in the bad zone area
After way to many hours of playing with this blank I decided to
cut
my losses. I threw out the glass so I wouldn't be tempted to play
any
more.
You should relate this tale to the guys at the ATM List
(atm@...) and the ATM_FREE group on Yahoo also. I think you
must have received some of Andre's early glass. There were reports
that he's improved over time...
I just finished building a furnace so I can fuse my own glass
blank.
The furnace cost me about the same as a good 20"blank. I fired it
up
yesterday for the first time. I'm waiting for a controller to come
in
for it.
Sounds like fun...
The next projects will be:
A trepan setup to cut glass disks.
A new grinding machine,
See my web page for ideas ( )
An interferometer the testing is almost done I need to make a 20 "
Plano mirror and a 4" spherical un coated f2 reference a beam
splitter and all of the hardware to hold it all together.
A box, a piece of window glass at 45 degrees, a green filter and
lightsource if you are going to be doing contact testing.
And then a vacuum setup.
Oh yea, let's not forget an awesome telescope:
Later
Ron
PS Ken do you know how I could do a 50% transmission silver
coating for the beam splitter.
James Lerch is the Silvering expert... Why size does it need to be? I
have a few half coated flat mirrors from a supermarket scanner about
2x4 inches or thereabouts.
Ken Hunter
