Namek and moons

[Vad]

No, I mean there'd have to be a moon, but I thought it was some form of unique energy that came off of the moon, as well as the Saiyan's artificial moon, that allowed them to transform.

Maybe I was wrong, but I thought that's what it was. If that's the case, I don't think you'd have to see the moon, just look in the general area where it sits in the sky in it's full state.

It is. It's a wave of energy that makes a Saiyan transform into an Oosaru. GT introduced that area of story. DBZ didn't delve into why the Saiyan transformed into the ape, just that it was the pinnacle of power and it happened either by false or full moon.