M20 THE TRIFID NEBULA

EMISSION AND REFLECTION NEBULA IN SAGITTARIUS

 (ra: 18:02 23 / dec -23:01,48)

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JULY 2010, Mercedes Observatory Buenos Aires, Argentina

DATA

TYPE: Emission, Reflection and Dark Nebula

VISUAL BRIGHTNESS: 9

SIZE: 29 x 27 arcs minutes

DISTANCE: between 2200 and 6000 light years

IMAGE INFORMATION

SCOPE: Celestron SCT working at f6.3 (roughly)

CAMERA: QSI 583 WS

GUIDING: Starlight Xpress Lodestar - William Optic 66 f6

IMAGE ACQUISITION: Maxim DL

FILTERS: Astronomik LRGB Type II 

SKY CONDITIONS: transparency good and seeing regular

EXPOSURES: LRGB (45,15,15,30) Luminance bin 1x1. RGB bin 2x2

PROCESSING: Median Combine in Images Plus, CCD Sharp, Photoshop CS2

OBJECT DESCRIPTION AND IMAGE SESSION

M20 is one of the attractions of the southern winter sky. It can be easily seen with 7x50 binoculars  even in relatively light polluted skies.  Its name came out of the reddish three lobed appearance which are ionized from the central star HN 40, a sextuple star system. Charles messier described it as a cluster of stars of 8 to 9 magnitude surrounded by nebulosity in 1764.

M20 is a unique combination of an open cluster of stars, an emission nebula (the lower, red portion), a reflection nebula (the upper, blue portion) and a dark nebula (the apparent 'gaps' within the emission nebula that cause the Trifid appearance; these are also designated Barnard 85). of three type of nebulosity if we also consider some dark nebula patches.