Sorry to be joining this discussion so late, but somehow the development of these detection radii on the galaxy map totally slipped my notice. Maybe i should have stayed active is the stealth/detection discussion longer, but it got mathematically arcane enough that i didn't have anything to contribute and lost interest.
But currently we have a situation were we have clever rules, but no good way to show the player how effective his detection actually is, without the clunky expedient of switching through different views that "assume X stealth". This IMHO is not a UI problem. This is a problem with game mechanics that have gone beyond what a UI can reasonably support. Unless there is a non-obvious solution to displaying this detection info... but i really doubt that there is.
I've suggested that a gradient be used so that a region of space in which you could see a ship of stealth 80 would be much more vividly coloured than a region of space in which you can only see a ship of stealth 10. This would make it extremely easy for the player to detect "gaps" in his detection where moderately stealthy ships could remain undetected. I've been told though, that this would be very difficult to code, though I think the extra utility it would give the UI would be worth it.
IMHO is not a great solution, but it may be about as good as is possible. It's going to be a lot more confusing when you get a bunch of overlapping detection ranges.
And what about the detection ranges of allies, or enemies who are thoroughly infiltrated by your spies? Are we going to have a rainbow mush of overlapping detection circles?
My recommendation would be to only show one empire's detection range at a time. The player can switch at any time between seeing his detection, and the detection of other empires (based on his visibility of their detectors). A small icon on the fleet and ship panels could be used to indicate which empires are known to have visibility of the particular fleet/ship.
I'd be posting in a design thread, but i wasn't able to find where these mechanics (for the galaxy map) were discussed.This thread
was the one that discussed stealth and detection mechanics for the galaxy map, and it's still open, though I'm not sure how likely it is for the decisions which were made based on that thread to be revisited.