You are designing a telescope to map far away stars. Given that our galaxy is 10^5 light years across and most stars are ~10 light years apart,
a)what diameter aperture do you need for mapping these stars? (assume that you are using visible light).
b)how large would the aperture have to be to distinguish binary stars (only 10^-7 light years apart)?

Question

You are designing a telescope to map far away stars. Given that our galaxy is 10^5 light years across and most stars are ~10 light years apart, 
a)what diameter aperture do you need for mapping these stars? (assume that you are using visible light).
b)how large would the aperture have to be to distinguish binary stars (only 10^-7 light years apart)?

anonymous · Answer

You haven't phrased your question well.

anonymous · Answer

I am given the formula $$M=\theta _{1}/{ \theta_{2} }$$
From my notes this is also equal to $$f_{a}/f _{b}$$ where f is the focal length of the lens in the telescope.
I do not know where to go from here.

anonymous · Answer

I believe what you want to use is the small-angle approximation to get an idea of the angular size of your separation. Then maybe use an angular resolution equation (airy disk) to try and solve for what diameter telescope would allow you to resolve such an angular separation for a given wavelength.

anonymous · Answer

Ok.