does anyone know how to use a spherometer

[faintfuzzies]

I bought a spherometer so i can watch my progress grinding a mirror at home. But I have no idea how to use it or how to figure out how to use it.

does anyone know how to figure this out and how to Figure out where on the dial a F5 would be.

I would like to learn the formula to figure all this out


Thanks

Lou

[bruce d]

Lou it will give you the radius of the curve in the mirror- would that be the same as the focal length? I think it will only be useful to you for rough grinding as i don't think the device will be accurate once you parabolize the figure, but that's maybe all you want it for.