I have CC2 and Campaign Cosmographer. Unless I'm mistaken, Cosmographer is officially for CC2 and not CC3. However, it is indeed another pack of add-ons and templates, which you could probably port into CC3 with some trouble. There are some space map related functions, which wouldn't work in CC3, I presume.
Cosmographer, by the way, is more or less tailored with Traveller specifically in mind. Many of the templates are actual Traveller sector maps, subsector maps and so on, and the iconography for representing systems on the maps is right out of Traveller.
I've looked at AutoRealm - it's pretty basic, and appears at a glance to be much less powerful than CC. CC does have a substantial learning curve, however. I have the benefit of some years of experience, so I'm comfortable with it.