Spherometer
A spherometer has been built in order to measure the radius of the mirror accurately and to make sure that it has ground spherical and does not have zones. Three legs were turned from brass in the lathe. Thread were cut at the one end and a ball bearing was soldered inside a hole on the other end. In hind sight it would have been better to have had screwed the three leg extensions on their sides instead of their widths since the spherometer would have been a lot stiffer. Now there is probably a measurable amount of sag in the middle due to the weight of the spherometer.
Here is photos of the spherometer:
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