The luna's secret continued

Go to the Gate (you unlock this when you unlock the Garden, the last dome you unlock) and you will be back in the place where you first got the ability to spin. You will find a Red Luma at the top of that kind-of castle thing that will let you use the Red Star to collect 100 Purple Coins. Some are in the air, some are on the ground, don't rush because it's not timed. Get them all and you will get a Star and you will be able to use the Red Star in the Observatory.



Hope it helps!!!!!

The soar mario is a red star that you can use when you unlock the top floor

You need to get to the Gate, which is unlocked after completing the 5th dome, the Engine Room. Go to the path on your right of the Engine Room until you get to where there is a house on a mini-planet with a 1-Up Shroom underneath it. Go inside the house and you will notice it looks familiar the first time you went there. Go on the platform where you met Rosalina and talk to her. Then a red Luma will talk to you and you will start a mission of collecting purple coins. The good thing is that there is a Red Star, so use it to fly to the purple coins. It would be a good idea to spin since spinning works to collect coins in air and on ground, but only on this level. Collect all 100 purple coins and the Red Power Star and the Red Flying Star is now availble to you in the Observatory.

The little star's secret is that you can get a red star by collecting 100 purple coins, after you've beat the Engine room. Rosaline will be somewhere else to talk to you, and will send you to another planet to collect the purple coins.

Go to a place called "the gate" that leads to gateway galaxy, available after unlocking "the garden" and select the mission "gateway's purple coins" When Mario enters the galaxy, Rosalina will meet. A Red Luma notices how much Rosalina trusts Mario, so he gives Mario the challenge of collecting 100 Purple Coins scattered around the planet to earn his trust as well. There are seventy coins on the planet and thirty in the air. Mario must use the new Red Star power-up(that's the luma's secret) that gives him the ability of flight to reach the thirty purple coins in the air. Completion of this mission will award Mario with the game's sole Red Power Star. One collected, it allows for use of the Red Star power-up in the Comet Observatory. Sadly, it cannot be use in other places apart from the obserbatory. It would be awesome, don't you agree?
Hope this helps!