Can any one tell that how the Telescope mirror is getting parabolic shape while grinding?
As the grinding tool and the glass are flat.
The action that you take while pushing the tool across the blank causes the curve. You don’t take full strokes across the blank and you rotate the tool frequently. Those two steps alone cause the tool and blank to generate a curve. It’s actually very had to grind an optically flat mirror.
http://www.scopemaking.net/mirror/mirror.htm
How to Clean your Telescope Mirror
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