NGC6888 Crescent nebula, PN G75.5+1.7 Soap bubble nebula and surroundings

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NGC6888, Crescent nebula - click for high resolution image
Object: NGC6888 - emission nebula, Cygnus
Coordinates: RA: 18h 54m 00s DE: +38° 10' 00" (J2000) (center of the image)
Location, date: Zubří u Nového Města na Moravě (19.5.2012), Bělečko (24.5.2012), Czech Republic
Telescope: newton 200/800 mm, reducer/corrector 2" ASA 2KORRR 0.73x
Focal lenght, speed: 585 mm, f/2.9
Camera: G2-8300 Moravian Instruments
Senzor: KAF-8300, 17.96 x 13.52 mm, pixel 5.4 um
Expozure: H-alpha:OIII = 250:250 min, bin 1x1
Filter: Astronomik EOS-clip filter H-alfa + OIII
Mount: Sky-Watcher EQ6-Pro SynScan
Pointer: Pentax SDHF, 75/500 mm

Nebula designated NGC6888 is also called Crescent nebula, according to its typical shape in small telescope. NGC6888 is located in the Cygnus constellation at a distance of about 4700 ly. Diameter of the nebula in longer part is 25 ly. Complex shape of the nebula is given by interaction of a strong stellar wind of central Wolf-Rayet star (WR 136, spectral type WN6) and slower moving gaseous envelope, which was blown away by the same star about 250.000 years ago [1]. Brightness of the nebula slowly decreasing, as the stellar wind blows it off to the interstellar space, however due to further fate of the central WR star, which awaits cataclysmic end as a supernova, it is likely, that sometime in the future, the nebula will be "switched on" again.

Vybrané galaxie v souhvězdí Panny - klikněte pro větší rozlišení
Soap Bubble nebula PN G75.5+1.7

This dim planetary nebula was discovered in 2008 by amateur astronomer Dave Jurasevich. Due to its symmetrical appearance it became known as "Soap bubble". Its almost perfect circular (globular) shape is rather exception among planetaries.

[1] A. Fernandez-Martín, D. Martín Gordón, J.M. Vílchez, E. Pérez Montero, A. Riera and S. F. Sánchez, 2012, Astronomy & Astrophysics