Defining Imperial astrography, or, "What's in a main?"

[Black Globe Generator]

Traveller identifies a main as a string of star systems separated by J-1, but I don't recall seeing a definition of how many systems consitute a main. Likewise terms like "arm" and "cluster" appear in different books, but I've never seen these defined with any degree of precision, either - for example, does a clump of a half-dozen J-1 worlds also constitute a main, or is this more properly a cluster, or is it both? I'm a bit confused.

Can anyone recommend a source with more detailed definitions of some of the astrographical terms used in Traveller?

 

[KrasnyKot]

Well, a main is somewhat defined as a group of worlds/star systems which are separated by no more than J-1. While not exactly defined this way, as far as I know, it implies a string of worlds.
A halfdozen systems would IMHO constitute no main as I think of it as a major trade route of sorts. I would prefer the designation armorfinger for such a short string of star systems. Or if they appear in a lump I'd call that a cluster, of course.
Just my Cr.02

Originally posted by Black Globe Generator:
Traveller identifies a main as a string of star systems separated by J-1, but I don't recall seeing a definition of how many systems consitute a main. Likewise terms like "arm" and "cluster" appear in different books, but I've never seen these defined with any degree of precision, either - for example, does a clump of a half-dozen J-1 worlds also constitute a main, or is this more properly a cluster, or is it both? I'm a bit confused.

Can anyone recommend a source with more detailed definitions of some of the astrographical terms used in Traveller?

 

[Black Globe Generator]

Originally posted by KrasnyKot:
Well, a main is somewhat defined as a group of worlds/star systems which are separated by no more than J-1. While not exactly defined this way, as far as I know, it implies a string of worlds.
A halfdozen systems would IMHO constitute no main as I think of it as a major trade route of sorts. I would prefer the designation armorfinger for such a short string of star systems. Or if they appear in a lump I'd call that a cluster, of course.
Just my Cr.02

I'm right there with you, KrasnyKot - I've used the working assumption that a main is a string of J-1 worlds that crosses at least three subsectors, and a cluster consists of at least four worlds with at least one world have no less than three J-1 companions.

I'd like to know how others have approached this, and if there are any OTU references to consider. Any other astrocartographers out there care to weigh in?

(And thanks for the reply, KrasnyKot.

)

 

[RandyT0001]

IMTU
A main is a string of worlds, primarily linear in arrangement, seperated by J1 and stretching across at least two sub-sectors. Usually mains have a significant number of worlds in them.

An arm is a string of worlds seperated by J1 that branch off a main into a new direction. Named arms connect the main to an important/rich/hi-tech/populous type of world. Arms have at a minimum of three worlds in it, not including the intersecting world on the main. Shorter links than three worlds are called spurs.

A cluster is a group of at least five worlds inter-connected by J1 but not connected to a main. The worlds of a cluster can occupy two or more different sub-sectors but are not primarily linear in arrangement. Most clusters are (somewhat) circular in arrangement.

Trees are strings of worlds connected in a linear arrangement that are shorter than mains but have arms that cross them. They can look similar to X's, Y's, I's, K's, F's and E's but are not limited to this. The longest (or the one with the important/rich/hi-tech, etc world on it) string of worlds of a tree is the stem. The offshoots are called branches. Trees might also contain small clusters in them called knots.

 

[Black Globe Generator]

Canon gives us rifts, which are areas mostly devoid of star systems (i.e. sparse density).

We also have void, as in Outrim Void - I take that to mean areas of sparsely scattered stars, that is, more than half of the worlds are J-2 or better apart. A possible alternate name for this might be drift, if that term hasn't been used elsewhere in astrography.

 

[Mickazoid]

There's another important association with the term 'a main'... it's a 'main' trade route.

IMTU, besides the astronomical term for the spiral arm of a galaxy (in which MTU is set) an 'arm' is often a astropolitical distinction. I prefer to use the terms 'clusters' and 'strings' of worlds.