[Spaceships] The value and realism of +24 if Silhouetted Against Deep Space . . .

[munin]

How large does the size-to-distance ratio have to be before the obscuring or lensing of background stars are useful ways to detect objects?

[Ulzgoroth]

Originally Posted by munin

How large does the size-to-distance ratio have to be before the obscuring or lensing of background stars are useful ways to detect objects?

Well, in principle at least not any larger than the background star, but you've got to be lucky enough to have it actually cross in front of one while you're watching.

One could figure out how big it has to be before it usually will obscure some, but I'm not going to try that now.

[kreios]

Echoing myself from Discord, we can use the WISE mission and 2016 WF9 as calibration.

WISE is a 660kg spacecraft, which we can approximate as 1t (and therefore SM+2), mounting a 10-system-sized telescope (effectively normal-sized for SM+4, therefore TL-5, therefore +3 bonus).

If we assume maximum time spent (30 minutes, +5), that WISE instead of scanning the whole sky 'zooms in' despite lack of an actual target (another +3), we get another +8.

Distance to target is at least 0.341AU (-63), size is at most a kilometre (+16).

Therefore, the total modifier is +16 (SM) +5 (time) -63 (range) +3 (sensor) + 3 (zoom) +24 (in space) +10 (in plain sight), for a final modifier of -2 [1], which does sound like a reasonable order of magnitude.


[1] And potentially a bit worse, since I'm assuming maximum size and minimum distance. Then again, you're probably dealing with skill levels of ~14-15.