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Headed out from Earth within the Solar System, Sol and Earth both may be used as reference.

When traveling in interstellar space with stellar systems themselves traveling at varying velocities even within the Local Cloud; it probably gets even more discombobulating at the scale of the Bubble ... and beyond - How would one navigate?

Say, we developed interstellar travel and were able to send a probe on a round-trip to a neighbouring system. The probe wouldn't be able to rely upon a history of it's outward trip because the systems would have moved a little during the journey. The same would probably apply to a beacon because of the lag involved. What could one use as a navigation reference? Is there an interstellar map with system velocities and stuff maintained somewhere?

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You would use the stars as your reference. Of course, some stars are more suited to this than others. For example, the Voyager Golden Records had pulsar maps, that in theory some alien civilisation could use to locate Earth (what could possibly go wrong?). So, stars with unique and easily recognisable characteristics make good 'landmarks' (in particular, pulsars).

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Wouldn't their position change over time too? –  Everyone Jul 13 '12 at 4:01
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@Everyone: I think you need to think a bit about the scale of things in these cases. How fast various stars are moving and how far away they are. Also consider that it will generally be possible to keep a constantly updating the database with fresh operations. Further, where do you want to go? If it is not to some visible (in some band) feature or to a spot defined in relation to such a feature I'd love to hear why. –  dmckee Jul 13 '12 at 4:21
    
@dmckee: There isn't a destination in mind just yet; it's merely a probable prerequisite for far space operations. A database update would also necessarily be limited to radio-speed; hence local. –  Everyone Aug 24 '12 at 8:02
    
The ship need not depend on database support from afar. They can carry their own instruments, and in any case on time scales less than many thousands of years you can get a very good approximation to the motion of the nearby objects before you leave. Nor will you pick just, say three stars to navigate by. You'll have a whole catalog of the buggers. Time and space scales matter, and your question seem to presuppose that things in the galaxy will move in a unpredictable way on time scales so fast that they can surprise the travelers. –  dmckee Aug 24 '12 at 14:55
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For interest, you could also use pulsars. I belive the idea here is that pulsars have unique and well-defined pulse times along with being bright, so you could use them as natural GPS satellites.

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