Need help combining gradients...

Hello all, I am new to this forum, and a beginner in photoshop.
Today I was trying to replicate the gradient effect i saw on a poster, which I thought wouldn't be that hard, but I was wrong.
I was drawing the earth and atmoshere at the bottom of the MUSE Resistance tour poster (See image attached)
Basically i drew the white planet, then the light gradient on a layer below it using the elliptical marquee and the darker gradient on a layer below the light gradient. The problem is I cannot get the two gradients to blend into each other like they do in the picture. I have tried using "foreground to transparent" gradients and layer masks unsuccessfully :mad: :confused:
Any suggestions on how to replicate the gradient accurately?

Why not use the gradient tool and do it all in one shot? After you get your elliptical marquee drawn, select your gradient tool. Sample the light blue for one end, the dark blue in the middle, and black on the other end. Then choose a radial gradient, and click and drag. Keep playing with your gradient sliders and the length of your gradient line when you click and drag until you get what you want. My guess is you'll have to use the transform tool to enlarge the gradient layer beyond the edges of your art to get that subtle curve, but otherwise, its a pretty straight forward job for the gradient tool.

My suggestion is that try blurring the LIGHT GRADIENT. Go to FILTER MENU, BLUR , GAUSSIAN BLUR and experiment with the Radius. If this helps visit me at http://www.becomeaphotoshopper.com/4-overview-steps-in-painting-hayley-williams/
Thanks :p