Just done eating her New Years Feast with Celestia, Luna was excited to relax and perform her duties of raising the moon. Tonight was a special occasion though. Tonight was a lunar eclipse. An extra special time where Celestia and Luna had to be in perfect harmony with one another in order to cast just the right shadow on the moon. This proved to be one of Luna's favorite nights. Not only do ponies gather to watch the moon slowly cast itself in a shadow, but she gets to spend some quality time with her sister as they work together.

Celestia's food coma had other plans in mind though. With no other options to move the sun into the proper position, Luna had to take flight and manually eclipse the moon. Certainly not one of her easiest flights. See if she helps out during the next solar eclipse.

Here you go. Enjoy! And with a cheesy little scenario/backstory I just thought of on the spot!