Denise Turner

McDonald Observatory

N 30 40.794', W 104 01.496';

Elevation 6240'

 

HOW DOES A TELESCOPE WORK?

Telescopes do two things that enable us to see distant objects:

 

When Galileo made the first telescope so many years ago, he used lenses to gather and focus light from the object he was observing.  Galileo's was a refracting telescope.  Unfortunately, using lenses caused a chromatic distortion (rainbow-like halo) around the object being viewed. 

 

This distortion in Galileo's refracting telescope caused Sir Isaac Newton to begin looking for a way to improve on the telescope.  He came up with an idea to use mirrors instead of lenses.  Using mirrors to gather and focus light eliminated the distortion seen in Galileo's telescope.  Many telescopes today use mirrors; these telescopes are called reflecting telescopes.

Simply put, a reflecting telescope uses a curved, primary mirror at one end to gather incoming light.  A smaller, flat, secondary mirror is located near the open end of the telescope and it reflects the light from the primary mirror into the eyepiece, which is located to one side.  The eyepiece contains a lens that spreads out (or magnifies) the light so that it takes up a large part of our retina.  That magnification is why our eyes are able to see something that is so very far away.

 

  

Before I went on this expedition, I had "learned" how a telescope works a number of times.  Trouble was, I never really understood...until I got to McDonald Observatory.  Dan Lester and Marc Wetzel did give us lots of information - not unlike the rapid-fire workshops where I had "learned" before.  And with them, I continued to have only inklings of understanding.  As we went into each telescope, though, and asked our many questions, I slowly came to be less overwhelmed and more awed.  Maybe the information had come too fast in the past and I hadn't had time (or opportunity) to fully process it all.  Maybe it's just a me-problem.  Whatever it was, spending an extended amount of time learning and experiencing made all the difference for me.  Getting up close and personal with those huge, marvelous instruments over a period of days AND hearing all the information from Dan and Marc was an incredible experience.  And to top it all off, we were given a telescope to take home for ourselves!!!  What a wonderful surprise that was!  Going out that evening and learning to use my telescope might have been the experience that cemented all that knowledge in place for me.

*Note: The telescope we were given is an Orion StarBlast.  #9814 4.5" Altazimuth Reflector Tabletop Telescope.  This telescope is an excellent beginner's telescope - even I was able to use it with ease, and I had never even touched a telescope before.  Thank you Shell Oil!

 

Thank you so much to everyone involved in making this experience possible.  This type of learning is so beneficial to teachers...how can we explain a concept or instrument to students unless we truly understand it ourselves?  Again, thank you,....