Interactive sky chart centred on 20 23 18.6 +40 18 05, with constellation stick figures overlaid. Locate shows the whole constellation with the target ringed; Field zooms to the close-up. Drag to pan, scroll to zoom, click any star to identify it. Imagery: DSS colour survey via CDS Aladin Lite. Constellation figures © Dominic Ford (GPLv3).
A vast emission nebula complex surrounding Sadr (γ Cygni), the star at the heart of the Northern Cross. The glowing hydrogen is split into bright lobes by intervening dark dust lanes — most strikingly the long curving channel that gives the brightest section its butterfly-wing appearance. Sadr itself lies in the foreground at around 1,800 light-years; the nebula sits far behind it at roughly 4,900, spanning well over 100 light-years across. One of the richest wide-field narrowband targets of the summer Milky Way, often framed alongside the open cluster NGC 6910 and the nearby Crescent Nebula.