If you're writing any kind of scientific paper in LaTeX, it will save you time in the long run if you use a reference manager. My tool of choice is Jabref.
Many journals require you to submit references with abbreviated journal names, the style of which may vary from journal to journal.
Fortunately, Jabref provides an easy means of toggling your Bibtex catalogue journal entries between full and abbreviated form - simply navigate to Tools -> Abbreviate journal names.
It's also possible to use your own custom list of journal abbreviations (Options -> Manage journal abbreviations). Since I couldn't find any ready made lists of abbreviations for astronomers, I created a repository at http://github.com/timstaley/jabref-astro-abbreviations.
It's pretty minimal at present - I've only provided an incomplete list of abbreviations in the MNRAS style. But I thought I'd raise a flagpole, in case anyone else finds themselves wanting this functionality. It's a start. Fork me!