NGC7822 star-forming complex in the constellation Cepheus is located about 3,000 light-years away from us. It contains Berkeley 59 star open cluster (in the upper right part of the nebulosity) that contains one of the hottest stars discovered within that distance. This is BD+66 1673 star – an eclipsing binary system containing an O5V type star with a surface temperature of about 45,000 K and a luminosity of about 100,000 times that of the Sun.

I have already imaged this area twice in the past, but both times only with a hydrogen alpha filter. This time I have used three narrowband filters that correspond to the hydrogen, oxygen, and sulfur elements. Plus some data was captured with RGB filters to show more or less natural colors of the stars. The actual NGC7822 (also known as Sh2-171 in the Sharpless catalog) nebulosity color is totally false – it was post-processed in a way to enhance and reveal the contrast between the areas containing different elements.

It is not yet clear which star is responsible for the illumination of that emission nebula. The bright star inside the bright nebula part (a little bit to the left of the center) is a foreground star located about five times closer to us than the nebula.

Sh2-171 nebula HSO palette
Sh2-171 nebula HSO palette
Image technical data:

Date: July-September 2022
Location: Nieborowice, Poland
Telescope: Tecnosky 90/540 Owl triplet
Corrector: TS FF/FR 0.8x
Camera: QHY268M
Mount: EQ6
Guiding: ASI290MM + Evoguide ED50
Exposure: about 20 hours through Ha, Oiii, Sii, and RGB filters
Conditions: Bortle 6, transparency medium-good, seeing medium