How Do Telescopes Magnify? School Level.

I'm looking for a good description of how telescopes magnify using
diagrams. No equations. I'd like to use it for 6-10th graders and some
lay people. From my physics books long ago, they would show an object
that passes through a lens (objective), and then into and out of an
eyepiece. Each stage would show the object as a vertical line (usually)
at various heights. I want to give this to some educators in about 2
hours who are conducting a class on telescopes. They seem baffled by the
idea. Well, if not at this time, then in a future week. By then I'll
probably have time to describe it to them.

I'm on Google looking, but nothing like what I want seems to be available.

On 12/16/09 3:05 PM, W. eWatson wrote:
I'm looking for a good description of how telescopes magnify using
diagrams. No equations. I'd like to use it for 6-10th graders and some
lay people. From my physics books long ago, they would show an object
that passes through a lens (objective), and then into and out of an
eyepiece. Each stage would show the object as a vertical line (usually)
at various heights. I want to give this to some educators in about 2
hours who are conducting a class on telescopes. They seem baffled by the
idea. Well, if not at this time, then in a future week. By then I'll
probably have time to describe it to them.

I'm on Google looking, but nothing like what I want seems to be available.

Try:

http://hyperphysics.phy-astr.gsu.edu...aydiag.html#c1
http://image.tutorvista.com/content/...ing-power.jpeg
http://www.vikdhillon.staff.shef.ac....nification.gif

"W. eWatson" wrote in message
...
I'm looking for a good description of how telescopes magnify using
diagrams. No equations. I'd like to use it for 6-10th graders and some lay
people. From my physics books long ago, they would show an object that
passes through a lens (objective), and then into and out of an eyepiece.
Each stage would show the object as a vertical line (usually) at various
heights. I want to give this to some educators in about 2 hours who are
conducting a class on telescopes. They seem baffled by the idea. Well, if
not at this time, then in a future week. By then I'll probably have time
to describe it to them.

I'm on Google looking, but nothing like what I want seems to be available.

Does it have to be a diagram?

Can you just get a long focal length lens and use it to form an image on a
piece of tracing paper.
The get a short focus lens and use it to magnify the tracing paper image.

You can then remove the tissue paper and show that you have really made a
telescope!

That is an excellent idea, and will illustrate the idea perfectly.

On Dec 16, 2:05*pm, "W. eWatson" wrote:
I'm looking for a good description of how telescopes magnify using
diagrams.

On my own web page, at

http://www.quadibloc.com/science/opt01.htm

you may find something helpful.

John Savard

OG wrote:


I'm looking for a good description of how telescopes magnify


Does it have to be a diagram?

Can you just get a long focal length lens and use it to form an image on
a piece of tracing paper.
The get a short focus lens and use it to magnify the tracing paper image.

You can then remove the tissue paper and show that you have really made
a telescope!

I like the practical approach to education too.

However telescopes don't magnify the image. The sun is about a million
miles in diam and in a telescope the image is about 1cm. A telescope
reduces the size of the object. What it does that we want is increase
the angular size of the image subtended at the eye over that of the object.

Joe

--
Joseph Mack NA3T EME(B,D), FM05lw North Carolina
jmack (at) wm7d (dot) net - azimuthal equidistant map
generator at http://www.wm7d.net/azproj.shtml
Homepage http://www.austintek.com/ It's GNU/Linux!

On Dec 16, 9:33*pm, Joseph Mack wrote:
However telescopes don't magnify the image. The sun is about a million
miles in diam and in a telescope the image is about 1cm. A telescope
reduces the size of the object. What it does that we want is increase
the angular size of the image subtended at the eye over that of the object.

"W. eWatson" wrote in
:

I'm looking for a good description of how telescopes magnify using
diagrams. No equations. I'd like to use it for 6-10th graders and some
lay people. From my physics books long ago, they would show an object
that passes through a lens (objective), and then into and out of an
eyepiece. Each stage would show the object as a vertical line
(usually) at various heights. I want to give this to some educators in
about 2 hours who are conducting a class on telescopes. They seem
baffled by the idea. Well, if not at this time, then in a future week.
By then I'll probably have time to describe it to them.

I'm on Google looking, but nothing like what I want seems to be
available.

Lens Combinations: Telescopes (click the hyperlink "astronomical
telescope" in the text).
http://www.mtholyoke.edu/
~mpeterso/classes/phys301/geomopti/twolenses.html

Exploratorium activity - How to make a telescope
http://www.exploratorium.edu/explori.../activity.html

A series of handouts I put together in 2006 for this purpose. Includes
online resource references.
http://fisherka.csolutionshosting.ne...htmatkit/MakeT
elesProject.html

These demonstrations work best with a bag of cheap lenses, eyeglasses,
hand-held magnifying glasses and/or a small make-up mirror as opposed to
ray tracing diagrams. You can use a two-hand held magnifiers, a hand-
held magnifier and a telescope eyepiece.

- Canopus56

On Dec 16, 7:33*pm, Joseph Mack wrote:
OG wrote:

Can you just get a long focal length lens and use it to form an image on
a piece of tracing paper.
The get a short focus lens and use it to magnify the tracing paper image.

You can then remove the tissue paper and show that you have really made
a telescope!

I like the practical approach to education too.

However telescopes don't magnify the image. The sun is about a million
miles in diam and in a telescope the image is about 1cm. A telescope
reduces the size of the object. What it does that we want is increase
the angular size of the image subtended at the eye over that of the object.

On Dec 16, 1:05 pm, "W. eWatson" wrote:
I'm looking for a good description of how telescopes magnify using
diagrams. No equations. I'd like to use it for 6-10th graders and some
lay people. From my physics books long ago, they would show an object
that passes through a lens (objective), and then into and out of an
eyepiece. Each stage would show the object as a vertical line (usually)
at various heights. I want to give this to some educators in about 2
hours who are conducting a class on telescopes. They seem baffled by the
idea. Well, if not at this time, then in a future week. By then I'll
probably have time to describe it to them.

I'm on Google looking, but nothing like what I want seems to be available.

Hi
Most of the suggestions jump right into
ray tracing with lenses. I think that isn't
really what you want to do.
Here is my suggestion:

1. Start with a pinhole projection. A real
demonstration is best here. This demonstrates
the concepts of projected image size, intensity
loss and ray tracing.
2. Bending light with glass. Best if done with
a block of glass and showing a beam traced through
the block.
3. Show how a lens is like a lot of pinholes that
bend the light depending on where the light goes
through the lens. Show focal point.
4. Show how the eyepiece is like a magnifying glass
to look closer at the projected image.

Dwight