There is something called image averageing or stacking for better overall noise reduction. I took this photo at 6400 ISO on my Canon 600D which is overkill but when you average 50 photos and use median alignment you will get almost noise free image with a lot of details. When I was taking, for example, Orion Nebula just by using lens, tripod and camera, I had to use around 500 exposures to get nice results at the end. :)There are software for this, it's called Sequator and it's completely free.