NGC 6871
NGC 6871 and the Tulip Nebula – islands of light in dark Cygnus
A thin veil of red light stretches across the star field, interrupted by branching dark veins, broad shadows and tiny, almost black tips. At lower left, the Tulip Nebula, Sh2-101, provides a bright accent; higher in the frame, the young cluster NGC 6871 emerges from the crowded stars. This field, about 3.85° wide, shows a layered stretch of the Milky Way in Cygnus rather than a single nebula with a clear boundary.
A tulip of glowing gas. Sh2-101 concentrates its light along a bright, curved rim. Hot stars, including HD 227018, supply the ultraviolet radiation that excites the gas. In this image, the pale inner arc and red outer envelope contrast with the dark dust strands immediately above them.
Young stars with powerful winds. NGC 6871 is an open cluster: a loose gathering, without the tightly packed appearance of a globular cluster. Studies using Gaia data place it in a wider group of young clusters. Its marked core contains WR 133 / HD 190918, a binary with a Wolf-Rayet component. The two stars remain unresolved here; the system hints at the very different evolutionary stages concealed behind similarly small points of light.
An ordinary-looking point with a famous companion. The position of Cygnus X-1 lies below the Tulip. In visible light, its marker identifies the companion star HD 226868. This photograph does not image the black hole itself, and the shock front known from much deeper exposures is not securely detected here. Farther down lies η Cygni, a K giant rendered strikingly bright and cool-toned in this processing.
The dark areas are part of the subject. Dust absorbs and scatters background light, creating regions with fewer visible stars and sharp silhouettes against the red glow. The close-ups include LDN 852, Barnard 146, DOBASHI 2269 and LDN 865. Their catalogue names refer to different parts of the field, not necessarily separate clouds at the same distance. In this orientation, north is to the right and east is up.
Where in the sky
The rectangle is this image's real field of view, with its measured rotation — not a symbol. Constellation figures and star positions come from SIMBAD.
6 entries sit within 26° of each other here — click a field to jump to it.
Crops
Tulip Nebula
Sh2-101 – the glowing Tulip
41.1′ × 32.1′·19h 59m 55.13s +35° 19′ 25.2″
A bright, curved rim encloses the pale interior of Sh2-101. Dark dust strands cross the red surroundings above it. HD 227018 lies within the marked nebular field and is one of the hot stars exciting its emission. This close-up concentrates on the Tulip; the companion star of Cygnus X-1 is just below its lower edge and is marked in the full image.
η Cygni
η Cygni – a bright foreground star
29.5′ × 24.3′·19h 56m 17.15s +35° 04′ 34.3″
The conspicuous point is η Cygni, classified in SIMBAD as a K0 giant. Its broad, softly fading glow stands out against the tiny background stars. The blue-white appearance in this HOO version is not a reliable natural stellar colour: the filter response and processing also shape it. The circle identifies the star, not a separate nebula.
NGC 6871 · WR 133
NGC 6871 – young stars and WR 133
38.8′ × 38.4′·20h 06m 01.91s +35° 48′ 07.9″
A loose group of bright stars emerges from the red veil: NGC 6871. The marker in its core identifies WR 133 / HD 190918, whose Wolf-Rayet and O-type components merge into a single point here. 27 Cygni, a separate catalogue star, appears farther towards the upper right of the close-up. The three markers distinguish the cluster area from individual prominent stars.
LDN 852
LDN 852 – dark fingers against red gas
36.0′ × 31.2′·20h 06m 20.51s +35° 10′ 28.7″
Slender dark fingers reach into an unevenly glowing field. The catalogue position of LDN 852 falls within this branching dust region. Its tips show the contrast between obscuration and the red background particularly well; farther out, the structures blend softly together. The circle locates the catalogued area rather than following its jagged silhouette.
B 146 · LDN 857
Barnard 146 and LDN 857 – hooks of dust
57.1′ × 54.9′·20h 03m 18.63s +35° 45′ 19.2″
This close-up links a broad dark band with narrower, hook-shaped extensions. Barnard 146 lies near the distinctive dark tip, with LDN 857 farther towards the lower right. Red light remains visible between them. The two catalogue positions help organise the scene, but their apparent proximity alone does not establish a shared distance.
DOBASHI 2269
DOBASHI 2269 – the great dark bay
1.08° × 0.93°·20h 03m 34.81s +36° 58′ 09.6″
A broad bay with relatively few visible stars opens between red nebular rims. The catalogue position of the dark cloud DOBASHI 2269 lies in its upper part. Farther down, the obscuration narrows into a curved band. The contrast between the nearly black interior, thin red strands and richer star fields gives this close-up a strong sense of depth.
LDN 865 · DWB 13
LDN 865 and DWB 13 – dust beside emission
1.18° × 0.83°·20h 04m 17.17s +37° 55′ 16.5″
In the right-hand part of the full image, finely branching red filaments meet softer dark patches. LDN 865 marks a dust-dominated region; the catalogued H II region DWB 13 lies farther to the right. Low surface brightness can reflect both obscuration and weaker emission. The markers distinguish the two catalogue objects without assigning the entire close-up to one nebula.
LDN 862 · LDN 863
LDN 862 and LDN 863 – along the upper cloud edge
1.27° × 0.38°·20h 07m 20.69s +36° 49′ 04.9″
This wide strip follows the upper edge of the image. Dark indentations alternate with red brightenings between LDN 862 and LDN 863, beside the position of DWB 5. The shallow framing emphasises subtle transitions along the edge. The overlaid circles provide search areas while the actual contours continue irregularly beyond them.
Acquisition and processing
Acquisition. Ten selected exposures from 5 September 2026, each 300 seconds long, provide 50 minutes of total integration. They were taken with the ZWO ASI2600MC Air on the RedCat 71 at 349 mm, gain 100, offset 50 and −10 °C, using a dual-band Hα/O III filter. All ten light frames were registered, locally normalised and integrated in the documented run of 9 September.
Calibration and processing. Calibration used a master bias, a dual-band flat and a library master dark scaled to 300 seconds. PiMagic received Hα = R and O III = ½(G + B), extracted from the integrated colour image. The documented workflow includes gradient correction, separate star and nebula layers, sharpening, noise reduction and nonlinear stretching. This entry uses the selected final AVIF version.
Reading the colours. In the HOO mapping, red represents the hydrogen-weighted channel, while green and blue represent the oxygen-weighted contribution. Dual-band colour-camera data are not fully separated spectral measurements; stellar colours and halos in particular should not be interpreted as natural broadband colours.
Annotations. The AVIF has its own astrometric solution: 6,248 × 4,176 pixels, 2.220″ per pixel and a field of approximately 3.85° × 2.57°. The solution used 27,361 reference stars with a residual of 1.10″. SIMBAD positions are projected through that solution into the image and its eight existing close-ups. Circles are locating aids, not measurements of cloud boundaries or stellar-system dimensions.