· Sagitta = approx 1/14"

· Template fits

· Have gone back and forth between #60 and #80 carbo to make tool and blank fit.

· Tool had annoying depression in center left over from rise (ironically).

· With strong chordal and W strokes, I've worn down the tool so that virtually all of the depression is gone.

· Tested RC and focal length with light reflection.

· Last night, it was about 114" inches (RC).

· Tonight, it was about 108 - 109".

· Will run tool on top with #80 for a few wets, then make another test.

· I believe that after this, I am ready for fine grinding, starting with #120.

· Clean off tool and entire work area.

· Put away #60 and #80, leaving no trace of them in work area.

· Use #120 to make tool and blank fit better.

· Completed about 12 wets with #120.

· Tool and mirror look good.

· Light test showed RC at around 1-9", so I did more grinding with tool on top.

· Later, the test showed RC at around 112-113" - a good value, 112" being just right.

· Probably will do about ten more wets with #120 before going to 220.

· Note: Berry's book says you should do about 40 wets with #120; whereas Howard's book says you should do only about 10-12, or roughly an hour.

· Basically, play it safe by erring on side of more wets.

· Expect to be grinding with 220 by Friday.

· Completed #120

· Radius of Curvature is about 111".

· Started #220 today

· After two wets (10 min. ea.) the pits from #120 are starting to show.

· Went for beer run.

· Started #320.

· Good size pits from #220 hanging around

· Completed #320

· Most pits are small and uniform.

· Cleaned work area, prepared for #500.

· RC is close to 112", near perfect.

· Tool and mirror fit is excellent. No binding at all.

· Mirror has velvety texture.

· Started with #500 carbo.

· Surface looks good.

· Spent Saturday/Sunday looking over Foucault Tester designs. Went to D. Donnelly's house. Great garage, lots of tools and building materials. Dick has a precise carriage for knife edge; it can be used with micrometer and should make the Tester work well. May be able to fit my micrometer with carriage; if not, will have to make a micrometer with knobs and tightly knurled screw.

· Have to build Foucault Tester ASAP.

· Built Foucault Tester using microwave spectrometer carriage, 6" dowel, angle bracket, aluminum baking tins and plywood. May need some improvement as things progress.

· Continued with #500. Surface looked great except for one intractable pit. It was a deep pit, perhaps from a piece of #220. I tried half a dozen wets and that pit was the only one remaining, a blight on the face of an otherwise perfect surface.

· To remove the pit, I backtracked to #320. Completed 8 wets as of this writing. Pit is shrinking, but stil there. I'm going back for another 2 or 3 wets, even though it is 11:20pm. I must get rid of that pit before proceeding back to #500 and beyond!

· Did 18 or more wets with #320. Pit is getting smaller, but it is a nasty bugger. Probably need six more wets to eliminate it, then, on to #500 again. Whew! Exhausted.

· During lunch, came home and did about 4 wets with #320. No more #320 left! But that gnarly pit is gone! It took as much work to get rid of that pit as it did to grind out the central depression with #s 60 and 80.

· Cleaned up tool. Recleated. Old cleats disintegrated due to pressed wood decomposition. Used three dowel slices. They're hard and solid. Tool looks good.

· Cleaned up work area. Then did five wets with #500. Baby soft feel is back. No discernable pits. Looking good. Plan on doing at least five more before going to #12 micron.

· Need to get tin for lighthouse on Foucault Tester. I hate the aluminum baking tins I now use. They're too flimsy.

· Based on ronchi tests, I did a cold press to prepare for a polishing session. I will do a long W stroke to figure the paraboloid. May have to do more than I initially thought. I think I have a turned edge, but I don't know if it is a bad thing at this point.

· Did two long W strokes, one about 5 minutes, other about 10 minutes.

· Seem to have a turned edge.

· Going to polish with tool on top.

· Foucault Tester is jiggly as a blob of jello.

· Ronchi tests jiggly as hell. Seems to take long time for me to remain still enough to perform the tests. Oh for a shop with an optical bench!

Conclusions:

· Testing apparatus sucks.

· Wiggling, wobbling, awful thing.

· No doughnut

11/21/92 09:46 PM

· Doughnut

· Did about 2 minutes of long W stroke, then cleaned mirror in cold water.

· Set it on rack, tested it, saw paraboloidal doughnut.

· Seems finished. Will check tomorrow, but I think this may be as close as I'm gonna get

· for this mirror.

· Might check it again tomorrow night, but foucault tester is so lousy I don't think I can use micrometer tests.

· Ronchi test showed a paraboloid, but light slit may have been to wide to get clean lines. I widened the other night.

· I hope I'm finished, if the shape changes, it's because of the temperature.

· See Epilogue further down.

· I modified the Foucault tester and the modification made all the difference. What did I do? Well, there were two problems: one, the movement of the carriage from left to right was done with my hand. I would try to inch it left, then right, as needed to manipulate the knife edge, cut into the cone of light, etc. This introduced a great deal of error into the situation, for the human hand is not very good at making precise movements of a few thousanths of an inch. Further, this problem aggrivated problem two: the wobbly stand on which I put my tester.

· To solve problem one I bought a joint connector (forget the exact name) which essentially is two eye bolts connected via a bridge with screw holes at each end. It is the kind of thing used to tighten a rope or wire. One of the eyebolts would attach to a wire which would in turn be attached to the leg of the carriage. Instead of using the other eyebolt for the knob, I bought a wingnut bolt, same size as eyebolt, to use for the knob. I then mounted this on the tester. One leg has an elastic band pulling it to the left; the other leg (right leg) has a wire attached to it and running through the eyebolt. On the far right of the eyebolt joint is the wingnut screw, which when turned left or right, moves the carriage left or right. This allows me to make very small, yet precise movements of the carriage/knife edge along the azmith. I also put a washer between the forward/reverse knob, the one that makes the knife go toward and backward from the mirror.

· I was just down stairs on the floor doing some preliminary testing. It is a bit uncomfortable on the floor, but at least there's no wobble! I positioned the tester such that the knife edge can move inside and outside the radius of curvature. I tried cutting the cone of light outside the RC, at RC, and then inside RC. I can manipulate the shadows such that they no longer bounce all over the place. In short, I CAN PERFORM A COMPLETE TEST ON THE MIRROR!!!!!!!!!

· I saw the upside down bowl, the doughnut, and what appears to be a paraboloid. Me happy!

· I loaded the micrometer at RC to zero. I can now conduct precise tests, measuring up to 250/1000s of an inch, well within the tolerances I need.