system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do we have such clear photos of galaxies that are a billion light years away?

I've just finished reading a book that was basically pictures of galaxies, stellar bodies, nebulas etc. from within our own solar system all the way to the intergalactic space a billion light years away. I know that they're taken with super powerful telescopes and that a lot of the photos are filtered under infrared and x-ray and all that but how does this all work? How are the telescopes able to do it? What kind of processing (if any) goes into the final version of the photos we see in books? How can we see things that are so far away?
gpt
Do an experiment for me.

Go to a random webpage that you've never seen before, glance at it for a split second, and close your eyes. Chances are you remember the general look of the site, but are fuzzy on the details.

Now open you eyes, and really study the page. Spend a minute or more just memorizing it, noting the specific layout, colors, words, font, everything.

Telecopes take really long exposures. Instead of doing a really fast "snap" shot, like a camera, they stare at a spot in the sky, sometimes for WEEKS at a time. They collect all of the super faint light; light that even the huge telescopes can barely see. They then take these weeks of light, and combine them all in to one image. They merge it all together to form a bright image; a picture that is thousands of times more clear and bright than a quick "glance" or "photo" would be.