As far as keeping your nav computer locked on to an astronomical object while you're actively checking out other ships and USSes? Not that I know of.
I have found, however, that the GPS (leftmost tab on the leftmost pane) is pretty useful for quickly re-selecting your intended navigational target in-system. Also, if you have a course plotted out of the current system, there will be an icon (it's a route icon, which resembles a "W") on the next system in your course, even if you change your current target. I stumbled across that while scanning planets in deep space. Makes ranking up Exploration much more pleasant than I expected.