Why Are Most Large Telescopes Reflectors, Not Refractors

question 39

Multiple Choice

Why are most large telescopes reflectors, not refractors?

• A)Large lenses deform under their own weight, but mirrors can be supported.
• B)Large mirrors need only one optical surface, achromats four surfaces to grind.
• C)Reflectors do not suffer from chromatic aberration like refractors do.
• D)Large, very clear lenses are harder to cast than more tolerant mirror blanks.
• E)All of the above are correct.