[ATM] mirror cells and parabola...

[Jim McPherson]

Hi Norm,
        Have you looked into PLOP to design a mirror cell? It will do 
all the math for you if you tell it what kind of mirror you have. I 
highly suggest it.

As to figuring. You will absolutely need to parabolize a 12" F/5 mirror! 
A spherical surface will not focus light coming from anywhere but the 
eye piece. Any other light (including light from stars) will NOT focus, 
it'll just kind of merge around the focal point but never come together. 
A parabola will actually focus light from the heavens into your eyes. 
The difference will be dramatic in the view from the eyepiece. A few 
nanometers difference here or there may not sound like much but the eye 
is more sensitive than you may think. As a WAG I would assert that a 
spherical 12" F/5 mirror would have less resolving power than a decent 
80mm scope. Sustaining 12x per inch would be difficult that leaves you 
at 144x Max. While a nicely made 80mm refractor can do 50x per inch and 
work at 150x.

Hope that helps.

-Jim

Norm Prince wrote:
> The twelve inch project is moving right along...have tool.. will
> grind..Horace has been handy to exchange ideas with on tile tools...(tips
> hat).
>
> But thats not why i'm typing.  I'm trying to think ahead a bit, and it
> occurs to me that i might need a pretty fancy cell involving some fancy math
> for what i'm seeing as a pretty darn thin chunk of what appears to be a
> pretty soft chunk of glass.  I've dug thru the archives some, but that is so
> tedious, and would be time better spent doodling up some sketches, or even 
> grinding for that matter.  If anyone would be so kind as to throw a dog a
> bone as to how/where to dig up some more fundamental info on this subject i 
> would be eternally greatful.
>
> I've been thinking about figuring too, and running some numbers...it seems
> to me that parabolizing an f/5 doesn't really buy me much.  Well at least as
> far as my eyeball is the limiting factor in the system.  The difference
> seems so miniscule that my eye wouldn't know the difference, tho i could be
> doing the math wrong as far as the Raleigh standard is concerned....  Does
> the correction help in other ways??? chromatically...etc.?
>
> -norm prince-
> Georgia, USA (land of bad seeing)
>
>
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