The California Nebula (NGC 1499) is an emission nebula located in the constellation Perseus. It is so named because it appears to resemble the outline of the State of California. It is almost 2.5° long on the sky, yet extremely difficult to observe visually. It's located about 1000 light years from earth in the Orion spiral arm of the Milky Way galaxy (where our Solar System is also located).

The California Nebula contains a hot blue-white star named Menkib (bottom center), by far the brightest star in this image. Menkib is one of the hottest stars visible in the night sky; its surface temperature is about 37,000 Kelvin (about 66,000 degrees Fahrenheit, or more than six times hotter than the Sun).

Menkib, which is receding from us at about 20 kilometers per second, is part of an association of very hot stars that were born from the California nebula only a few million years ago. These massive and luminous stars are lighting up the nebula, as well as heating and ionizing it. In visible light, the ionized gas glows red, while in infrared light we see the heated dust.

I spent five nights capturing the image, 21 hours total of data acquisition. There are 8.5 hours of Hydrogen Alpha data and 6.25 hours each of SII and 0III data. Seeing was quite good all three nights, as there is very little transparency to see through the nebula. The image was color assigned using Hubble Palette, preliminary processing and calibration was done with APP and final processing was done with Pixinsight and Lightroom.

OTA: William Optics GT81 using 0.8x Flat6A-81 reducer
Mount: Celestron CGX-L
Camera: ZWO ASI2600MM Pro
Gain: 100
Cooling Temperature: -10 degrees celsius

Filters (Chroma 3nm):
Sii 🟢 25 x 900s
Ha 🔴 34 x 900s 
Oii 🔵 25 x 900s
21 hours total data acquisition

Auto-guiding: ZWO ASI174MM Mini and ZWO M48 OAG
Control: ZWO ASIAIR Pro
Calibrated in Astro Pixel Processor⁣ with darks and flats
Processed in Pixinsight and Lightroom

Location: Bortle Class 4 skies near downtown Flagstaff, Arizona