From: Don Bates 
To: atm{at}shore.net
Reply-To: Don Bates 


--0-1552520504-1051722477=:8124
Content-Type: text/plain; charset=us-ascii
Content-Id:
Content-Disposition: inline


After exactly 5 months of steady work, I am ready to call it a day for my
10" f6.6 plate glass primary. This was my first time to work with a
thin plate (3/4") piece of glass. My goal was to create the best
surface I could using a mirror that would reach ambient temperature as
quickly as possible for planetary observing. Here is what I got for the
last set of readings:

TEX - 1/28.0 wave at zone 2
Couder - 1/28.0599 at zone 2
6 Tests - 0.997 Strehl / 2.5 RMS

Needless to say, I take these with a grain of salt due to the variability
of the knife-edge test. But, star test indicated similar discs on both
sides of focus, with distinct rings. Ronchi pointed to a slight
turned-edge, but I'm still not sure on that one. All in all, I would say
the surface is as good as I can make it. My web cam images indicate a
smooth surface with no problem zones. Combined with my ultra-flat Quartz
secondary and baffled tube with fan, the detail on Mars this summer should
be very nice indeed.


I would like to thank all the folks in the Group that gave me such good
advice. This is a strange and frustrating hobby, but if you make it to the
end of the road, there is a real sense of accomplishment. I don't think I
will make another one (my wife is still complaining about the rouge stains
in the carpet)but hopefully this mirror will last a lifetime. Things I
learned:
1) Use larger unglazed tiles for the grinding surface. 2) Buy more pitch
than you think you could ever use because you WILL use it.
3) Dental stone is hard to find and kind of pricy, but make an excellent
tool that will survive the grinding/polishing process.
4) Don't try to scrape and re-use pitch, it will turn into a nasty
substance that will stick to your mirror. 5) Make sure you get a good fit
across the entire surface of the mirror when making your pitch lap. Don't
expect the middle to work its way into contact. If it doesn't make contact
in the middle right after pouring, do the lap all over again. 6) Digital
cameras are excellent for taking pictures of the surface during the
foucault test. You can see more detail in your digital pix than with the
naked eye.
7) Once your lap get too thin (1/16 inch) bite the bullet and pour another
one. Yes, its a hassle, but you are wasting your time with a thin lap, and
will probably create a nasty problem with the surface. 8) Gugolz pith is
nasty, awful stuff. Although many ATMs swear by it, I had nothing but
trouble. Stick to a good quality pure Burgandy pith. The clear amber stuff
is particularly nice.
9) No matter how you slice it, Pitch and Rouge are nasty substances that
are guaranteed to get you in trouble with your significant other. But just
like making mud pies as a kid, it is kind of fun to make a mess once and a
while...

Clear Skies and Perfect Parabolas,

Don R. Bates


__________________________________
Do you Yahoo!?
The New Yahoo! Search - Faster. Easier. Bingo. http://search.yahoo.com
--0-1552520504-1051722477=:8124
Content-Type: text/plain; name="BatesfinalTex.txt"
Content-Description: BatesfinalTex.txt
Content-Disposition: inline; filename="BatesfinalTex.txt"


        TEXEREAU MIRROR TEST SHEET

           Comments: Bates 254mm Final Figure   Optical diameter: 9.75
  Readings per zone: 4
Radius of curvature: 131
                f/D:  6.72
   Diffraction disc: 0.000177031

 1 ZONE                1          2          3          4
 2 h(x)              2.4375     3.4471     4.2219     4.8750
 3 h(m)              1.2188     2.9423     3.8345     4.5484
 4 hm**2/R           0.0113     0.0661     0.1122     0.1579
 5 hm/4f             0.0047     0.0112     0.0146     0.0174
 6 D1                0.5687     0.6313     0.6685     0.7210
 7 D2                0.5687     0.6313     0.6685     0.7210
 8 D12               0.5687     0.6313     0.6685     0.7210
 9 D12 -  0.5601     0.0086     0.0711     0.1084     0.1609
10 Lamda c          -0.0027     0.0050    -0.0039     0.0029
11 Lamda f * 1e5      -1.26       5.66      -5.66       5.12
12 Lamda f / rho     -0.071      0.320     -0.320      0.289
13 u * 1E6             0.19      -0.86       0.86      -0.78
14 Wavefront           0.00      -0.77       0.00      -0.41
        Reference parabola: y = -0.0170886 * x**2 + 0.571338
        passing through (  2.44,  0.00) and (  4.22,  0.00)

Maximum wavefront error = 1 / 28.0 wave at zone 2

Results for individual sets of readings:
        Reading set 1: 1 / 19.6 lamda, Max Trans Abberation=0.38
        Reading set 2: 1 / 21.9 lamda, Max Trans Abberation=0.22
        Reading set 3: 1 / 15.3 lamda, Max Trans Abberation=0.73
        Reading set 4: 1 / 19.3 lamda, Max Trans Abberation=0.51

--0-1552520504-1051722477=:8124--

--- BBBS/NT v4.00 MP