Photographing the galactic core of the Milky Way requires a specific combination of astronomical and meteorological conditions: the sun must be deep below the horizon (astronomical twilight, below -18 degrees), the moon must be absent or very dim (below 10% illumination is excellent, below 30% acceptable), and the sky must be nearly cloudless (below 15% cover).
Inverza also checks that the galactic center is at least 10 degrees above the horizon - below that altitude, atmospheric extinction makes the core too dim to photograph effectively. The scoring weighs galactic altitude, sky darkness, moon interference, and cloud cover.