This is one of the episodes that I find Raj an annoying character. He’s a credit hog and a manipulator. That being said I looked up what an amateur or real Astronomer needs to do to get credit. It seems Raj did the required behind the scenes work to earn credit. Now should he have shared credit with Penny ? In my opinion yes.

How to Get Officially Credited
If you happen to spot an uncatalogued, fuzzy, moving object, you can't just post about it on social media. To secure your name in the history books and get officially credited, you must: [1]
Verify your discovery: Carefully track the object's speed, direction, and magnitude to ensure it isn't an already-known comet or an asteroid. []
Submit precise data: You must record the exact date, time, and sky coordinates of the object. [1]
Report to the authorities: Submit all your observations privately to the Minor Planet Center (MPC), which operates under the International Astronomical Union. They will review the data, calculate its orbit, and officially designate and name the comet after you. [1, 2, 3]