Will copy what I said a few comments down since it seems to be confuzzling.
"It's not a cannon, it's a dish with a bubble of water in it that refracts the light into it's colorful spectrum, then collects it.
Meant to be a science-fiction-y way to explain how they make rainbows."
"Science fiction is fun. Take real priciples, but have a few over-the-top elements for craziness.
A city that is pulling up water from below the clouds, using the magnified heat of the sun to boil that water for steam to then suspend the city? Use steam jetted ramparts (reference my architecture picture) as a propulsion source for the pegasi to travel around their city? Collect lightning via lightning rods and wind large air funnels and air compressors?
They're cool way to look at it, yet completely impractical. All what steampunk is about."
Also figure I'll add that as far as science fiction goes, the mass effect is easily my favorite made up science (even though I don't care that much for the games). Steam power is right behind that. Just watch steamboy, very cool idea there.
I would say the addition of Rainbow Dash in the foreground makes this cooler, but that sounds lame from the whole 20% cooler thing.
The platform makes a nice streampunk.
This would be an interesting theme to work with, although I might be inclined to include some Da Vinci designs to the overall structure like they did for some aerial units in the game, Rise of Legends.