The rules state that -60 is the greatest negative modifier you can face and +60 is the greatest positive. They are unclear on two points 1. whether or not skill raises and the talented talent are calculated into the +60 limit and whether or not the max is -60+60 = 0 or -60 +120 = +60. In any event the book states that plotting a course without the astronomicron is a hellish -60 task. This got me thiking.

Dark Age of Technology

Warpsbane Hull +10% Navigation Rolls

Two Assistant Navigators +20% Navigation (+1 level of success of successful see page 232).

Exceptional Charts +20%

Ancient Almanac Astrae Dvinitus (i.e. Nav Comp) +10%

= +60%

Going beyond charted Space

Without charts might want to be on a cruiser for the +5% bonus from a ship masters bridge. Add in a Talented Navigator (this is an exploration mission after all) and you got -5%.

And in the present timeline, if you can't get good charts a Runecaster is a great idea (though it's a xeno artifact).

Conclusion: The Astronomicon makes ships much cheaper to build (warpsbane hulls not mandatory) and cuts the required number of navigators. The real question is, if you offset the penalty for not being able to see the astronomicron (or nearly offset it) do you use the standard navigation rules instead of requiring that the navigator make the roll?

Dal Thrax said:

For skill advances and the Talented talent, they should be considered part of the 'baseline' value; the modifier is applied after this.

For maximum limits, I'd work out all modifiers first, and then cap it at +/-60 once that's all resolved.

Dal Thrax said:

It's a given that it should be possible to travel the warp without the Astronomicon - afterall, other species manage it all the time, and humanity achieved it both with and without Navigators long before the Emperor established the Astronomicon.

Beyond that, as I read the relevant section, it says that anything that might offset the penalty for charting a course without being able to see the Astronomicon applies only at GM's discretion, so those bonuses aren't a given. Beyond that, the way I read it is that you make a test to chart a course one way or another. If you can find the Astronomicon, then you take the test (an Ordinary (+10) Perception Test; though personally I rule all awareness and perception tests for Navigating the Warp as being psyniscience tests instead; it just seems more appropriate), with +/-10 on that test per degree of success/failure respectively. If the Astronomicon can't be found, then that same test to chart a course becomes Hellish (-60) instead. The only thing that changes, then, is the difficulty of the test to chart a course.

A Navigator should always look for the Astronomicon anyway; it is always easier to navigate by it than it is to go without, even if you've got an array of tools, etc, that could reduce the penalty they would otherwise suffer for navigating without the Astronomicon.

Well canocially the default Rogue trader setting is at the very limits of the Astronomicrons reach (about 5000ly) with significant portions of the setting possibly being beyond it (or with the beacon blocked behind standing warp storms). Considering that navigational problems are perhaps the main reason the sector in not part of the Imperium, I suspect many rogue traders are going to be interested in Navigational aids.

I'm pretty sure that a Warpsbane hull (armored hull) and a Runecaster (xeno artifact) will apply to navigation roles regardless of the ability to see the astronomicron (in fact this could be one of the major uses of a runecaster). That gives +30, unless you're willing to overule the teamwork rules that puts the player at +50 to a navigation role (or -10 overall modifier). That really isn't looking all that bad.

Dal Thrax said:

I'm aware of that. Of course, a good chunk of the Imperium (out towards Ultramar) is beyond the reach of the Astronomicon as well, because Terra isn't in the centre of the galaxy, so there's a lot more of the Eastern Fringe outside the beacon's range than there is of the northern, southern and western reaches of the Imperium.

Dal Thrax said:

It's still worse than having the Astronomicon visible, though, which is of course the point of the Astronomicon in the first place - it makes Warp Travel easier.

The BFG rulebook mentions smaller astronomicons used as beacons for ships in tircky warp-passages. Not sure how canon this still is, but a few astropaths focused on one thing might extend for a couple of light-years.

It makes sense that astronomicons existed before The Emperor, as is it heavily implied that He created the navigator gene. Unless (Like the Golden Throne) they were originally intended for a different purpose, The Emperor had no reason to make them.

Navigator's make use of the Astronomicon, but don't actually require it (though they really do like it), as the Navigator gene allows them to see the Immaterium, which the Astronomicon is a lighthouse into, providing a point of reference. So the Emperor had reason to create both, independently and seperately. A lighthouse is useful without a telescope, and vice versa, but both are infinately more useful together (to stick to the nautical analogy).

St. Jimmy said:

Heretic! Blasphemer! (just kidding...)

There is only one Astronomicon. Before Him, there weren't any. (The Emperor/Astronomicon simply allowed humanity to spread through the Galaxy at a much faster rate, allowing the Great Crusade to take place. Remember humanity had already been to the farthest reaches, but it took a loooonnnngggg time for them to get there).

There are outposts (like in the novel 'Blind') called Astropathic Relay Stations, where a bunch of Astropaths (called a choir) re-broadcasts the Astronomicon to extend the range. Like a Repeater on a TCP/IP network. But they have to be inside the Halo.

All the Astronomicon allows Navigators to do is jump farther and safer per jump, that's all. They can still navigate short distances without it. For really short jumps along a known route, you don't even need a Navigator. Your ship's cogitator can steer you. (Hold on while I make the calculations for Light Speed...- Han Solo)

Now say 100 'Hail Celestines" and sin no more!