Astronomy/telescope

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Expert: Steven LJ Russo - 2/8/2004


Question
hello, I was given a few dozen homework questions by my professor and I am stuck on just this one question, can you can help me out? here it is:

Why are most large telescopes reflectors, not refractors?
1. Large refractors do not transmit enough light.
2. Large lenses deform under their own weight, while large mirrors can be supported.
3. It takes too long to make refractors.
4. The lenses in refractors often crack

thanks a lot  

Answer
Hi Steve:

The reason is that since glass is a VERY slowly moving liquid, over time, it will deform.  No problem for a reflector, as it can be supported from below.  But a refractor lens can only be supported on its edges.  So the largest refractor ever built is the 40 inch in at the Yerkes Observatory in Green Bay Wisconsin, while the lergest single mirror is the 236 inch in Russia, and the 200 inch in California.

Steve

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Steven LJ Russo

Expertise

As a space science educator in a planetarium, my work centers around teaching people about the night sky and the solar system. I have a strong background in those areas, plus the history of NASA and spaceflight, and meteorology.

Experience

Experience in the area. I have been an amateur astronomer for 47 years, and have been teachng space science in planetariums for 34 years. For 15 years I was a radio and television meteorologist, and for the past 20 years I have been a space science writer for two newspapers in New York State. I am a member of the Middle Atlantic Planetarium Society and the International Planetarium Society. I have had a number of articles published in several astronomy journals, including "The Constellation" and the "Planetarian". Education/Credentials. I hold a B. S. from Wagner College and an M. S. from State University of New York at Oswego. Awards and Honors. I have been awarded the "Fellows" award from the International Planetarium Society for more than 20 years of continuous service in the planetarium field.

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