Tools
1. The vacuum pan. I will describe this in a separate post.
2. One inch micrometer to measure the wedge of the corrector plate. We want to keep the wedge to less them then .001" Enco sells imported micrometers for as little as $10.00.
3. Dial indecater that reads to .0001". The corrector plate will be deflected in the range of .002" to .007". Enco has one listed for $39.95.
4. Convex grinding tool to grind the plate. I used a tile and plaster tool. The tool was generated by grinding the back of my primary mirror blank against it. To generate my larger 16" tool I glued a 1/2 inch plate glass disk to a plaster disk and ground it against the tool. Remember the tool will be convex in the range of .002" to .007" almost flat. Use the spherometer to check this accuratly. You can stop fine grinding at about grit 500.
5. Special spherometer which has to be made to made to fit the plate diameter. The spherometer should be large enough to just set inside the edges of the plate. I built what I call a hybrid two footed spherometer. A third leg at 90 deg. from the center like a (T) shape is added so it will stand up leaving both hands free.
l--l l l Top view l l Spherometer l l l l Made of 1/4"X3/4" steel bar stock l l -------------- -------------- l ( O ) l ------------------------------ ^ Dial indecator
( ) ( ) Front view l ------------------------------- ------------------------------- ll ll ll ll ll ll ^ ball bearing on each ^ rear leg foot
You can replace the dial indecater with a micrometer head and have a great two footed spherometer to measure the sagitta of most any mirror. For this you will have to measure the distance accuratly between the balls. (Advanced Telescopes Making Techniques Vol 2 p100).
6. Your lungs. No you do not need a vacuum pump to pull the little vacuum that will be needed.
My next post will cover the vacuum pan. Just stay tuned to this channel Bob Pfaff