Foucault test question

Started by wress, 10/01/2002 02:03PM
Posted 10/01/2002 02:03PM Opening Post
Please help me understand something. I've read that the actual center of curvature for a mirror is the average of the distances from your eye to the mirror and the light source to the mirror. Theoretically, if you place your eye at the same distance they are the same. The question is, how do you ensure that your eye is placed consistently in the same position for each reading? It seems that since you are taking very precise measurements, a small movement of your head could result in a huge error. Am I missing something? Thanks in advance and clear skies.

Bill
Posted 10/01/2002 11:32PM #1
Thansk Ed. The reason I'm asking is that I just finished building a "slitless" tester using directions from the Stellefane website. They didn't provide directions for its use but it is set up such that the light source and the knife edge move together. So far I've only used it with a Ronchi grating, and it works well with that. The strange thing is that when the light source and knife edge are stationary, I can move my eye forward and backward from behing the viewing window and see the text book shadow patterns vary on the surface of the mirror. Do you or anybody else know of a good reference book that explains the use of the slitless configuration. I have only read about the classic tester that has a stationary light source and a moving knife edge. I'm about ready to build another tester.