You’ll never imagine 😉
While some people pay $55 millions to get a week (source) on the space station, I explored gas giants, gas clouds, entire suns, planets, neutron stars and black holes with my mind’s eye 😀
It pays to have a beautiful imagination and the sole answer for how that is done, is being able to picture with your mind’s eyes, what you read in a book and expand from there. It also helps to not forget your inner child ^^