Phalanx? Are fleets deployed from a moon to a planet show up in the phalanx?
Or maybe gather more Intel. If you have been spying on someone for a week, try to include the log in times. There is usually a 3 hr sleep time. Then attack just before his usual log in time. If he had fleet saved on recycle or transport mission, his fleet would be returning by now. It would be hard to try a ninja.
The problem is when when you have timed your attack when he had an all nighter.
If he is online gauge, the distance of his nearest planet and his engine levels. Compare this to your own. Will he be able to move a fleet to his planet earlier than your fleet can attack it? If he has a moon, does it have a jump-gate.
Does he have an ACS depo? Does he have any allies nearby? Do you think they are online?
Most people also have a single main fleet and some small raiders. Have you seen his main fleet parked on a planet? Is it in this Galaxy?
Intel... Knowledge is Power.
I'm still a newbie so don't take this things too seriously.