How and when to use the Piscis Austrinus card?

[Gooras]

I tried it before I mark the stars on any constelation, but when turn was over stardust is not returned... Are the Grand stars excluded from the Piscis Austrinus card effect?

[Alternauta]

I wonder the same thing. It's not obvious when to use this card as you can't use cards after star observation.

[Kayvon]

It's in the rules. You can only use abilities on your unexhausted Constellations at the beginning of your turn.

If you merit any stardust, it's credited to you automatically afterwards and included as a log message.