[ATM] baseline roc on a mirror with lost data..

[Dan]

Thanks Richard,

That was my original idea, just wasn't sure if it would queer my numbers (my 
effing tape measure probably wont get to within the .008" that I need 
though, as that is the ke movement of the averaged center zone r), as I 
wanted to use the "average" r of the center zone, but as others have pointed 
out I reckon I can just call that zero and go from there, as the ke movement 
must be the same in either direction no matter what fixed point I use as 
Dale stated.

Norm

-----Original Message----- 
From: Richard
Sent: Thursday, April 19, 2012 2:03 AM
To: 'Dan'
Subject: RE: [ATM] baseline roc on a mirror with lost data..

Why not measure the big radius R with a tape measure?   The difference
between the zones of your parabola will be too small to show on the tape
measure; but you can accurately measure the DIFFERENCE between zones with
your effing eff tester.

-----Original Message-----
From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf Of
Dan
Sent: Wednesday, April 18, 2012 5:14 PM
To: atm at atmlist.net
Subject: [ATM] baseline roc on a mirror with lost data..

Hey Yall,

Its been a long time since I posted for various reasons but now I find
myself in a terrible place.

I took a loooong time off on the 12" f/5 I am making, and in that time my
computer went belly up with all the spreadsheets and data with it. (lectures
about backing up your data aside..........)

so, my question is how do I find a Zero point Roc in order to process my
Couder results given that the average r for the center zone is not
zero?...that is to say..how do I come up with a Zero from an Roc that I
cannot measure as a sphere since I have already started parabolizing, and no
longer have a sphere, with the additional caveat that all my original data
is lost? (and that I still want to achieve the desired goal...a 12" f/5)...I
can't exactly say that what I ground and polished is EXACTLY what I was
shooting for...it could be anywhere from an f/4.9 to a f/5.1 and those are
silly numbers (and for that matter I couldn't care less...I'm going for
mighty close..not exact..I'm aiming only for Rayeidh Standard)...they could
be BIGGER!!!!!! deviations...uhg.

anyone?..please help!

Your faithful enthusiast, and biggest dullard lurker that tries!

Norm

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