[ATM] Re: ATM Digest, Vol 17, Issue 10

["Arjan te Marvelde" <arjan.te.marvelde@hetnet.nl>]

Yeah, formulae were right, but I filled in the wrong x value in the sphere
one.
I said it could be wrong, didn't I?
It's just like my daughter, she does understand math but screws up tapping
it in on the calculator.

Cheers,
Arjan


> This sounds reasonable to me- it is in the right "order of magnitude"-
Arjan
> must have just made a mistake somewhere with some term. Anyone can do that
> (I am so stupid with math that no one would want to trust me with
> calculations for a trip to the moon- we'd smash on the rocks).-

> Arjan wrote:
> > > Equivalent formulae (equal paraxial ROC = R) would be:
> > > sphere:     x^2 + (y-R)^2 = R^2, or y = R - sqrt(R^2 - x^2)
> > > parabola:  y = (x^2)/2R
> > >
> > > so for x = radius = 5.5m and R = 33, the sag would be
> > > sphere:    929.8 mm
> > > parabola: 458.3 mm
> > >
> > > This deduction may, of course, be wrong.
...
> > .sagitta (Y, r, -1)
> [1] 458.3333
>
> ... and the sphere:
>
> > .sagitta (Y, r, 0)
> [1] 461.5612
>
> So, the difference is 3.228 mm

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