How did Palpatine learn Yoda was on Moraband?

Question

At the end of Clone Wars TV show, Yoda is sent to Moraband by Force Priestesses, as part of his trials for learning Force ghost ability. There he encounters ghosts of ancient Sith, and they tell him:

There is no life after death. Only nothingness awaits you, Jedi. Your fear feeds our hunger for power. They will know you are here. We will tell them. You will die and be nothing.

Official explanation is that these ghosts are not real, because Sith truly cannot live after death. Instead, they are just illusions, presumably created by Priestesses to test Yoda.

But later we learn that Palpatine is really alerted to Yoda's presence on Moraband. He and Dooku then try to "break" Yoda and fail. Yet, the question remains: how did Palpatine learn that Yoda is on Moraband if Sith ghosts were not real? I doubt Force Priestesses would cooperate with him (maybe I'm wrong :) )

Answer 1

Through Dooku’s connection to him

It is because Dooku had a strong connection to Yoda (having served as his apprentice for many years) that he could sense the presence of Yoda:

PALPATINE: Only the presence of someone significant to you would allow you to sense this ripple through time and space.

DOOKU: My old master, Yoda.

PALPATINE: Yes. Master Yoda has come to Moraband, although why, I do not know.

_{The Clone Wars, “Sacrifice”}

The implication is that it was Dooku who sensed Yoda’s presence on Moraband. That said, a previous scene seems to indicate that Palpatine told Dooku to return to Coruscant before Dooku was able to communicate with him, though the scene still heavily implies that Dooku has sensed Yoda’s presence (as explicitly confirmed later).

Perhaps Palpatine sensed Yoda’s presence separately, whether through his strength in the Force or the presence of the dark side on Moraband, or both, or perhaps he merely noted the perturbation in his apprentice through the Force (if Dooku is connected to Yoda, Palpatine is doubtless connected to Dooku). This latter possibility is borne out through the assertion that “only the presence of someone significant to Dooku” could allow him to sense Yoda’s arrival. If this is the case, for Palpatine to have sensed it directly seems improbable.

Of course, Dooku could not have sensed Yoda’s arrival just anywhere, even with that connection. Only a planet so strong in the dark side of the Force would have triggered his senses.