Artist's comment:
A screenshot from the Moonrise animation, with princess Celestia raising the Sun.
A couple tidbits about the animation process, in case you're interested:
Animating her mane and tail was a challenge. Early on, I attempted to use a ripple effect in After Effects to generate them; that didn't work so well, and I eventually settled on a less lazy approach. I used temporary circles as guides for the waves in her hair and carefully drew every 4th frame or so. I then connected those frames with shape tweens, but then turned all the tweens into keyframes and manually adjusted them. The resulting blob was copied and recolored and masked many times to generate the spectrum of colors in her hair.
I find that very slow motions, such as Celestia's wavy hair or a basic pony walk cycle, are actually harder to animate than quick motions, like a running cycle. If a frame in an animation cycle is a little bit off, the jitter is much more noticeable in a slow movement than in a quick one.
To save time, I used Celestia's mane and tail animations as a base for Luna's.
The horn aura was generated in After Effects using a bunch of simple chokers and turbulent displace effects.