Some Diagrams of How the Light is Gathered :

A Refracting Telescope uses lenses to bend the light :

A Reflecting Telescope uses a mirror to gather the light :

A Cassegrain Telescope has a Secondary Reflector (mirror) to move the focal point :

Ground-Based Optical Telescopes
 

Kitt Peak National Observatory - winter scene

The 4 meter (diameter) telescope at Kitt Peak :

The mirror of the 4m telescope :

A newer and much larger telescope is the Gemini 8 meter in Hawaii :

An even larger telescope is under construction in Arizona.  This is the Large Binocular Telescope (LBT), which has two 8.4m (331 inch) mirrors that work together to form an image with the combined aperture of both (effectively a 468 inch mirror).   Go to the LBT web site.   The University of Minnesota is a partner in building and operating the LBT.  University faculty and grad students will do observing projects with the LBT as soon as construction is complete.

Radio Telescopes

The NRAO Green Bank Telescope :

The size of the GBT compared with US landmarks :

How a Radio Telescope works :

The Arecibo Telescope has an aperture of 22 acres, by far the largest in the world:

for more Arecibo images see this NAIC images or the main NAIC home page.

The NRAO Very Large Array (VLA) interferometer :

Another view of the central part of the array :

The VLA antennas can be moved as far as 25 km apart :

The Very Long Baseline Array (VLBA) has the highest resolution of any telescope ever built :

Here is one of the antennas up close (in North Liberty, Iowa) :

Space-Based Telescopes

At some wavelengths we cannot do astronomy from the ground because the atmosphere is opaque to that form of electromagnetic radiation.  This is particularly severe in the infrared, ultraviolet,  X-rays and gamma rays.  To observe these forms of radiation we must put telescopes in space.

Here is a chart of what fraction of radiation coming from space passes through the atmosphere, for different wavelengths :

Optical :

The Hubble Space Telescope has a relatively small mirror (2.4m = 94 inch), but it gets better resolution than any ground based optical telescope because it is not limited by scintillation in the earth's atmosphere.  Here it is being unloaded from the Space Shuttle :

The Chandra X-ray Observatory :

The Compton Gamma Ray Observatory:

The Space Infrared Telescope Facility :