Question

You have been awarded one hour on a 2m telescope equipped with a detector of 45% net quantum efficiency. This system will yield 100 photons per second from your target star. You are given the choice of upgrading to either

(a) a detector with twice the efficiency or

(b) a telescope with twice the aperture.

Which would you choose? Present a numerical justification in your explanation

Answer 1

(a) will be the choice of upgrading in this case. According to the formula of the Quantum efficiency we have:

The current set up has an efficiency of 45% which when replaced with a detector that has twice the efficiency we have twice the number of electrons being collected as the number of incident photons is constant. While in case of increasing the aperture to twice it's size we are only increasing the number of incident photons but the number of electrons being collected remains same which doesn't improves the net quantum efficiency. Thus (a) is the right choice.