NGC 281 - Pacman nebula in Cassiopeia

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NGC281 - click for hi resolution image
Object: NGC 281 - emission nebula, Cassiopeia
Coordinates: RA: 00h 53m 00.0s DE:+56° 37' 00" (J2000)
Location, date: Bělečko (23.8.2011), Jedlová v Orlických horách (25.8.2011), 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-alfa : OIII = 130:250 min, bin 1x1, bicolor technique
Filter: Astronomik EOS-clip filter H-alpha + OIII
Mount: Sky-Watcher EQ6-Pro SynScan
Pointer: Pentax SDHF, 75/500 mm

Pacman nebula belongs between famous objects of the northern hemisphere in distance of about 9500 light years from Earth. Diameter of the nebula in space is about 130 light years. It is relatively bright emission nebula with dark dust lanes, globulae, pillars and star-forming region (IC 1590) in the nebula centre. The young very hot stars in a star cluster gives nebula energy to glow. Intense radiation (mainly in ultraviolet part of spectrum) and strong star wind erodes interior of the nebula which gives it shell like appearence and makes intersting pillar structures. Bok globule Conspicuous dust cluster in the center of the nebula is "Bok globule", kind of object named after astronomer Bart Bok.

NGC 281 is best observable from dark sky places with medium to high aperture scopes through UHC or OIII filter. The image was processed using bicolor technique (R=Ha, G=Ha+OIII, B=OIII) which was brought by Steve Cannistra. As clearly seen from the image, outer areas of the nebula radiates in red light at hydrogen alpha emission line (656.281 nm), whereas in the center dominates radiation of doubly ionized oxygen (495.9 and 500.7 nm).