The apparent magnitude of objects in the sky determines their brightness when we see images of them through a telescope.  No money in the world can buy you more brightness when looking at objects in the sky.  The brightness of an object when looking through a telescope is what it is.  There is a cheap way to cheat yourself into brighter images when photographing the sky though, but more on that later.

Telescopes have a larger aperture than our eyes so you might expect they collect more light and hence show brighter images, and they do!  But telescopes also magnify images and therefore spread the light over a larger image giving you exactly the same brightness but in a bigger image.

DeepSkyVideos has a great video showing how Andromeda now faintly visible in the night sky, will be crashing into the Milky Way in 4 billion years from now.  As Andromeda will get closer, the surface brightness does not go up as the light will be spread out over a bigger area.

Exposure & Stacking Images

When you look through a telescope, you only the image you see.  In astrophotography, you can take images with longer exposures.  The camera for the time of the exposure collects light before visualizing the result in an image using the accumulated light.

Not only can an astrophotographer take images with longer exposures, with special software, but an astrophotographer can also overlay many images over each other.  This increases the amount of collected light per area even more.  Such images can be taken sequentially the same night, but also over many months.

But for now, I am trying to figure out what telescope to get myself.  More on these techniques once I will investigate astrophotography myself.