Re: [ATM] marking the center of a circle

[Joe <nss@mwt.net>]

Nils Olof Carlin wrote:

>>That will give you the center of a circle, but will it give you the
>>center of the mirror?
>>The center of the mirror must not necessarily coincide with the
>>center of the glass.
>>    
>>
>
>With machine figured mirrors, well centered during figuring, I believe the 
>centers coincide closely in practice. With "hand"-figured mirrors, not quite 
>as surely, though I have yet to hear a report of significant difference (a 
>center spot being significantly offset from the glass center seems much more 
>likely!).
>  
>

I would think the chance of the center of revolution being different 
than the physical center of the mirror having a greater chance of 
happening in a machine mirror than a hand made one. due to how do you 
hold a mirror by hand in the EXACT same place all  the time?
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