Have you noticed the sweet new dragon? I bet you want me to tell you how to hatch a Solar Eclipse Dragon now... ok, here goes. The best (fastest) combination is Blazing + Lava, so chosen because both of those dragons are easily acquired, and they have the lowest average breeding time. If you are curious about why that matters, check out my post on best breeding combinations.
# Update: It has been proven that Blazing is not required, so Air has been substituted (slight time advantage). Better breed quick!
Breeding Pair: Air Dragon + Lava Dragon
Breeding Time: 48 hours or 38 hours 24 min with upgrade
Availability: Till November 19th
Type: Sun/Moon
Price: 2250 Gems (like you'd really pay that)