accuracy(?) in astrography (was: RE: [FT universe] was [URL] ...)

The Man, Oerjan, writes:

>> Ah Oerjan, but I had heard suggested that the approach from a star to
>> a star was:
>> leaving - small jumps to clear gravity well of star
>> large intermediate hop
>> arriving - a series of small, more accurate jumps as you close in
>
>Um... I read it (the FB FTL description) more as "accuracy is a
function
>of jump range and presence of gravity wells" - you need to begin and
end
>each journey with a series of short jumps *because* the accuracy is
shot
>by the presence of the gravity well. You try making a long jump right
up
>to the FTL limit of the gravity well, you risk going a bit too far and
>get destroyed - or, almost as bad, get thrown somewhere else entirely.
>
>> So if you made your last jumps small, accurate ones, you could
>> place/find such a cache.
>>
>> N'est pas?
>
>May work, yes. I'm not sure how accurate deep-space astrography is -
this
>is another limiting factor in the jump accuracy, and probably the most
>important here. Indy, comments?

Well, your accuracy is only as good as your detection capability,
assuming
your jump engines can put you in a spot that is relatively small (say,
within a few hundred kilometers of where you want to be). I mean, if you
know *exactly* where something is, and your jump engines can put you
close
to a given spot, you're golden, n'est-ce pas? (oh, geez, now Tom's got
me
doing it!).

To put all this in perspective, go find a huge room, like an auditorium
or an
indoor sports arena. Scatter around this room a dozen baseballs or
something
similar. Those'll represent star systems. Now take a grain of sand,
representing your deep-space cache. Place it somewhere in the room, not
anywhere near one of the balls. Go away for a week. Come back and try
and
find it again. If you had the foresight to make an accurate map of where
the
grain of sand is relative to all the detectable stars, you should be
able to
get back to it again (this assumes your jump technology is such that
it'll
allow this kind of accuracy). Otherwise...

Anyway, Oerjan asked about accuracy in astrography. The accuracy is only
as
good as what you can see/detect. There's plenty of undetected 'dark
matter' out
there (comets ejected from solar systems, burnt out stars, etc) to play
havoc
with things if they come close enough. And the move we study the
universe at
large, the more we learn and refine our sky maps. Accuracy is dependent
on
the detection technology of the time.

Now most of you know the stars won't have moved very much relative to
one
another in a course of 1000 or so years, so once you've got them
pinpointed,
they really won't move very far in the course of a given campaign. For
example,
our own sun is heading in the general direction of Vega, which lies ~27
lightyears away, at a butt-kicking speed of 12 miles/second.

We may actually get there one day...

Mk
------------------------------------------------------------------------
---
If the conquest of a great peak brings moments of exultation and bliss,
which in the monotonous, materialistic existence of modern times nothing
else can approach, it also presents great dangers.  It is not the goal
of
*grand alpinisme* to face peril, but it is one of the tests one must 
undergo to deserve the joy of rising for an instant above the state of 
crawling grubs.
				       -Lionel Terray, 1965