From: "Kenneth L. Hunter" 
To: atm{at}shore.net
Reply-To: "Kenneth L. Hunter" 


An easier way to do this would be to download my spherometer spreadsheet from:

http://groups.yahoo.com/group/atm_free/files/Sphero/

Get the Sphero.zip file, unzip it, and from there it's easy!

Ken Hunter



"Dwight K. Elvey" wrote:

> Hi
>  I don't think your calculations are correct? For an
> 8" F8, my calculations say that a 3.5" diameter spherometer
> should read a little shy of .012". Here is my calculations:
>
>  8" f8 has a focal length of 8" * 8 = 64". This
> is a ROC of 2 * 64" = 128"
>
> Using right triangles and 3.5" I get the equation:
>
> (128 - x)^2 + (3.5/2)^2 = 128^2
>
> This expands to:
>
> x^2 - 256*x + 3.0625 = 0
>
> I used one one of the net quadratic equation calculators to
> get:
>
>  x = 0.01196
>
> See:
>
> http://www.math.com/students/calculators/source/quadratic.htm
>
> or use:
>
>  x= ( -b +- sqroot(b^2-4ac) ) / 2a
>
>  on your own calculator.
>
> Later
> Dwight
>
> >From: "James P Crombie" 
> >
> >The .006" was with the 3.5" spherometer, if you
calculate it out it
> >translate to about .048" across the 8" of the mirror. 
So I have another
> >.002" to go for an f8
> >
> >Frank Q wrote:
> >
> >>Hi All
> >>
> >>An excellent effort.
> >>
> >>I have a question -- My recollections of grinding an 8" f/5 is that
> >>I could excavate much more than 0.006" in a few hours - does
> >>anybody else find this or is my memory rapidly failing?
> >>
> >>(I used 80 grit and a full sized plate glass tool)
> >>
> >>Cheers
> >>Frank Q
> >>
> >>----- Original Message -----
> >>From: "James P Crombie" 
> >>To: "Atm List" 
> >>Sent: Wednesday, July 23, 2003 3:38 PM
> >>Subject: ATM Mirror Grinder pictures
> >>
> >>
> >>
> >>
> >>>Hello all
> >>>I did another couple of hours with the mirror grinding
machine and got
> >>>the sagita to .006"(this is with a 3.5"
spherometer not overall ) or a
> >>>ROC of  166" .   I thought I would start with
something easy like an 8"/f8
> >>>
> >>>http://www.jamescrombie.com/temp/closeupmirror1.jpg
> >>>http://www.jamescrombie.com/temp/wideview1.jpg
> >>>http://www.jamescrombie.com/temp/mirrorgrinder1.avi    (note 1.7mg)
> >>>http://www.jamescrombie.com/temp/mirrorgrinder2.gif    
(same as above
> >>>but will open in browser window)
> >>>
> >>>--
>
>>>--------------------------------------------------------------------------
> >>>
> >>>James P Crombie
> >>>
> >>>Summerside      Machinist
> >>>Prince Edward Island      Amateur Astronomer
> >>>Canada      3D Designer
> >>>
> >>>E-mail      jpcrombie{at}pei.eastlink.ca
> >>>Astronomy webpage      http://www.jamescrombie.com
> >>>Rhinoceros 3D webpage      http://www.jamescrombie.com/rhino/
> >>>Mirror Grinder page          http://www.jamescrombie.com/pics/
>
>>>--------------------------------------------------------------------------
> >>>
> >>>
> >>>
> >>>
> >>
> >>
> >>
> >>
> >
> >--
> >--------------------------------------------------------------------------
> >
> >James P Crombie
> >
> >Summerside                  Machinist
> >Prince Edward Island        Amateur Astronomer
> >Canada                      3D Designer
> >
> >E-mail                      jpcrombie{at}pei.eastlink.ca
> >Astronomy webpage           http://www.jamescrombie.com
> >Rhinoceros 3D webpage       http://www.jamescrombie.com/rhino/
> >Mirror Grinder page          http://www.jamescrombie.com/pics/
> >--------------------------------------------------------------------------
> >
> >
> >
> >

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