Question

What are the difficulties in using large and ground based optical telescopes?

• A. Chromatic aberration
• B. Large lenses are very heavy and tend to get distorted
• C. Cannot be used during the day time
• D. Very noisy

Answer 1

Answer: (A), (B), (C)

The correct options are
A Chromatic aberration
B Large lenses are very heavy and tend to get distorted
C Cannot be used during the day time

Difficulties faced by making and using ground-based optical telescope are:
1. Objective lens of the telescope should be large so that it captures maximum possible light. However, large lenses are very difficult to make, are very heavy and tend to distort.
2. The length of the telescope is very high (proportional to the size of the lenses).
3. The images formed by lenses have errors of colours. This is called chromatic aberration.
4. Optical telescopes can be used only during the day. Even in nights, city lights and cloudy weather can make their operation difficult.
5. Light rays reaching the earth undergo bending due to refraction by atmosphere. This bending keeps changing because atmosphere is not constant and the apparent position of the heavenly bodies keep changing.