California Nebula

About the object

The California Nebula in Perseus, a long band of glowing hydrogen whose outline really does resemble the state on a map. The gas is lit by the nearby hot star Xi Persei, one of the hottest stars visible to the eye. The nebula is large, almost five Moon diameters long, but very faint in visible light: the eye cannot see it even under a dark sky, while a dual-band filter and long exposures pull it out even from the city.

Distance: about 1,000 light-years, apparent size in the sky: 2,5° × 0,5°, constellation Perseus.

How it was shot

Everything here was shot with a DWARF Mini smart telescope from a balcony in a city in Ukraine: light-polluted sky, only the eastern half of it visible, and a roof overhang that cuts off the south. 3 nights (1 night in August and 2 in September), 3 sessions, 190 frames with exposures of 90, 120 and 180 s, a dual-band Hα/OIII filter that passes only the glow of hydrogen and oxygen and blocks most of the city light pollution. The stack holds 5 h 1 min of light; the longest night, 22 August, gave 2 h 10 min. The goal for this object is 4 h, and it is reached. First night 23 August 2026, last one 21 September 2026.

California Nebula in the night log: 22 August, 16 September, 20 September.

How it went

California became a test of long exposures: 90, 120 and 180 seconds in one night to see where the device starts losing frames to tracking and light pollution. The nebula turned out to be rewarding: hydrogen in dual-band shows up even with the Moon out. The three-night frame gathered enough light to show the whole band, and the object is closed in the challenge.