Re: [FH] FTL, astronomy

"laserlight@quixnet.net" wrote:
> 
> Quoth I:
> > No pulsars close by, are there?  I'd like we'd use nearby bright
stars eg Sirius--the closer they are, the easier it is to judge your
exact position.
> > (If you're trying to get the right driveway, you might estimate from
the end of the block--not from the Eiffel Tower, as even though it
stands out well, it's a bit too far away).
> 
> Quoth Indy:
> >Nice analogy, but for space navigation, doesn't quite work. Star
> brightness is irrelevant to distance, so if you pop into an unknown
> area of space, it won't work at all trying to figure out whether that
> bright star you see is nearby and not.
> 
> I was thinking of triangulating from multiple stars.	Pulksars would
be more idetifiable, I suppose, especially if you're travelling long
distances.  Siruis is not going to hard to find in you're in
human-occupied space in the GZG verse, though is it? Call it 20 parsecs
or so.

20 parsecs is a lot! 64+ lightyears. Sirius is going to dim noticeably
in
that distance. At 10 parsecs Sirius is a 1.4 mag star. Double the
distance
and it is going to get Sirius-ly lost in all the other stars. You can
calculate it out (oops! WARNING!! math formula approaching!!!) by
plugging
in the numbers:

	 m = M - 5 + 5 * log (d)

Where M is the absolute magnitude (1.4 in the case of Sirius), d is
the distance in parsecs, and m is the apparent magnitude.

The next problem would be trying to determine what stars around you are
"nearby", and how you would go about doing that. The most
straight-forward
way would be parallax by taking measurements from 2 widely seperated
locations. That involves (usually) taking a measurement, moving the ship
somewhere (like 1 AU or more is good), taking another measurement, then
calculating. The moving thing is going to take all your time. And if you
are pressed for time, or rather immobile...