Re: ATM Power formula

["Richard Schwartz" <richas@earthlink.net>]

A microscope and a telescope are fundmentally different.   In a telescope,
parallel rays enter, and parallel rays exit (and go into your eye).   In a
telescope, the power is defined for slightly off axis rays as the departure
angle divided by the entry angle.

But in a microscope, the entering rays diverge from a very close point.
They are transformed into parallel rays that enter your eye.

So what exactly you mean by the "power" of a microscope, I am not sure.
Comparing a displacement of a point source to an angel of divergence is like
comparing apples to oranges.

In all optical devices, the wavelength of light is a limiting factor.   You
are not going to see much detail smaller than the wavelength of light times
the f-ratio in the focal plane.   The wavelength of light is about 20
microinches  (aw, nuts, I did it again; make that .5 microns).  So in an f/5
telescope, you are limited in the focal plane to details of about 2.5
microns, or 0.0001 inches, if your wife has a good figure and the seeing is
OK.

In a microscope, the objective lenses are highly engineered devices that are
typically f/1.   So the finest detail you are likely to see is about 0.5
microns, or .000020 inches.

Note that McCarthy, the creator of LISP and a noted figure in artificial
intelligence technology had a past life where he developed a scanning
optical microscope that could push this limit.

. . . Richard (on a slow ATM day)

----- Original Message -----
From: "Kevin M Whitefire" <kwhitefire@juno.com>
To: <mayen1@mwt.net>; <atm@shore.net>
Sent: Tuesday, December 12, 2000 12:59 PM
Subject: Re: ATM Power formula


>
>
> What is going on in a Microscope?  we are talking
> about a very short focal length here of the primary.
> And I mean how about close focus?  the higher power
> objective lens used the even closer it gets to the
> object being viewed.  I don't know why but this has me
> all confused as to what is going on.
>
> What I think is going on in a microscope is this:
>
> In a telescope, the surface of the objective is covered with a layer of
> air about 600 miles thick, where in the microscope, it might be a few
> millimeters thick.  Air disturbing the microscope isn't quite as bad as
> in the telescope, where it looks like you're looking through a fun-house
> mirror in many cases.  I've seen excellent seeing only in the American
> Southwest, before one enters California by interstate 10.  The 50x per
> inch might be usable here, or I might get brave and push it even higher.
> However, I live in Eastern Iowa, and if there's no cloud cover I might
> get to use my richest field eyepiece and see some lunar features with my
> 8" Newt.  I might be able to see the Pleiades or get a poke at the
> Hyades, or if I'm really lucky, M42 with a moment or two of clear
> viewing.
>
> Well, it's not that bad.  I might get a couple of nights of clear sky a
> week, and an hour or two of dead air to look through out of those.  Light
> pollution isn't that bad here, but the air does boil a lot.
>
> Kevin of Eastern Iowa
> Seeker of the Darkness
>
> "When Reason defies Reasoning, sit down, shut up, observe, and take
> notes.  There will be a test on this material."
>
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