Question

If you want to make a very dim object appear much brighter in an image photographed through a telescope, which of the following factors are important?

a. diameter of the telescope and the length of the exposure
b. length of the photographic exposure only
c. diameter of the telescope only
d. length of the telescopic tube only

Answer 1

a. diameter of the telescope and the length of the exposure

Both the size of the telescope as well as the length of the exposure are important. It should be clear that each helps to maximize the number of photons collected, which makes the image appear brighter.