Since about 1900 all new telescopes that have been constructed for state-of-the-
ID: 1554752 • Letter: S
Question
Since about 1900 all new telescopes that have been constructed for state-of-the-art astronomy are reflecting telescopes. No old refracting telescopes are currently in use for anything other than some planetary studies. Why has the reflecting telescope become the only contender? [Hint: astronomers want to see dimmer and dimmer, more and more distant objects.]
1. The mirror can be as large as you want.
2. Mirrors can be made more easily than lenses can be made.
3. Mirrors have fewer optical defects than lenses.
4. It is just a way of paying tribute to the greatness of Isaac Newton.
5. The tubes of large refracting telescopes need to be so long that they are difficult to support.
Explanation / Answer
The answer is option 1.
This is because we can make a much bigger aperture in a reflecting telescope as the size and weight is a limiting factor in making a telescope. In refracting type of telescope, very large lenses are very heavy but it is very easy to build a large size thin mirror or a segmented mirror.