Aurora Borealis Sky Technique

I wanted to give a try at a really beautiful technique I saw recently.  I didn't know exactly how it was created, but I thought I would try layering colors from light to dark to get that beautiful northern lights look.  My first attempt looks a little more like an alien abduction, but it's cool too.

So, on the 2nd try I wanted to go with some different colors added in to give the illusion of colors streaking across the sky.  I think it's pretty fun!  What do you think?

I started by using Shimmery White card stock and lightly sponging in Sky Blue, and then layering in Marina Mist, Dapper Denim and Night of Navy.  I also added in a Archival Black to deepen the shadows.  The stamp set I used was Lovely as a Tree, and also a couple sentiments from the Rose Wonder Stamp set.  In a way, I wanted to not have any sentiment on these cards, but the more I looked at it, the more I loved the technique, but also thought it was a bit blank.  Sometimes it's hard to know when to stop.