If you notice a faint glow around Leo, up to Gemini, you aren’t imagining it.

It’s the Zodiac Lights.

The 12 constellations of the Zodiac run along the Ecliptic – the plane of the Solar System. That plane is filled with all of the left over dust and what not from the formation of the Planets. On very dark, i.e., Moonless, nights, you can see the sunlight reflected off of that dust in the form of a faint glow. And since the Ecliptic is pretty high up this time of year, and the New Moon isn’t for another week, this is a good time to see the Lights.