Nebulae from a balcony

Nebulae are the most rewarding targets for a city. Most of them glow in the narrow lines of hydrogen and oxygen, and a dual-band filter passes exactly those lines while blocking most of the street-light glow. That is why the Rosette, the Heart or California show up better from a balcony than any galaxy.

The price is time: under a city sky every nebula needs four to eight hours of total exposure, gathered over several nights. Below are all the nebulae of the challenge: captured, in progress and those still waiting for their season.