Re: ATM Off axis Parabolas

["Andrew Schott" <aschott@cfl.rr.com>]

Always with the negative vibes!  Now, if I build it, I'm too old to use it!

Gee, thanks Bob. ;)

----- Original Message -----
From: "Bob May" <bobmay@nethere.com>
To: <atm@shore.net>
Sent: Monday, December 31, 2001 1:03 PM
Subject: Re: ATM Off axis Parabolas


>
> The eye will correct for the spherical error and it's that change of
> curvature that generates the counter astigmitism.  It makes it easy to
have
> the 0 curvature error at the center as this is where the basic focusing is
> defined.  As you go further from that point along the astigmitism axis,
the
> focal length gets shorter/longer and the normal youthful eye corrects for
> that change of focal length automatically.  In older people, the eye
doesn't
> change as much and thus you will notice that they tend to center the
target
> of their viewing much more than a younger person will.
> Bob May
> http://nav.to/bobmay
> bobmay@nethere.com
> NEW! http://bobmay.astronomy.net
>
>
>