There are two ways to go, really. If you are interested in nebula, and faint objects like that, you need a lot of light gathering power but not as much magnification. If you are interested in the planets and higher resolution, the focal length of the primary is the most important. For nebula, a Dobsonian is a good way to go, also called "light buckets". For planets, a Maksutov (or "Mak") is a good way to go. For planets, you need a good quality tripod as well, motor driven is nice but not essential. If you can give your preferences and a budget, I would try to recommend some choices for you. You could step up a little to a larger refractor, like a 75mm achromat, that would be better for both uses.