----- Original Message ----- From: <[EMAIL PROTECTED]>
To: <pentax-discuss@pdml.net>
Sent: Thursday, January 13, 2005 4:56 PM
Subject: Re: Astrophotography (was Re: *istD EOL...)
I find telescope eyepieces work pretty much as intuition suggests; a "stronger" eyepiece increases the magnification of the image. A far more interesting question, to my mind, is why that isn't the case in photography.
Bob Blakely mused:
Ok, the analogy using "light levers" didn't work. Let's try again...
Nothing is working opposite to expectations. One lens, the objective lens,
is working in one direction with light coming in from the distant object at
the *distant* focal point to the image on the other side of the lens at its
*close* focal point. The other lens is being used the other way around with
the light from the image going from the *close* focal point to the more
distant focal point and eventually to your eye.
Regards, Bob...
From: "Tom C" <[EMAIL PROTECTED]>
> OK, I understand the math and don't disagree, but why does a longer > focal
> length eyepiece (a set of glass lenses in a tube) give lower > magification,
> when a longer focal length camera lens (a set of glass lenses in a > tube)
> yields a higher magnification?
>
> It would seem at first blush that if you have a telescope with a given
> focal length producing x magnification and you then viewed that image
> through 2 eyepieces of different focal lengths, that the eyepiece with > the
> longer focal length would yield the higher magnification. What makes > it
> work opposite of what one (I) would expect?
>
> I know this is a basic optics question that I'm just not too > embarrassed
> to ask.
