See the full gallery on Posterous

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See the full gallery on Posterous

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NGC 4945 is a prominent 8.6 magnitude galaxy located about 12m light years away in the constellation Centaurus. It forms part of a nearby (Centaurus A/M83) group of galaxies that includes NGC 5128 (Centaurus A), and M83. It is viewed nearly edge-on and is marked by thick dust lanes obscuring an active galactic nucleus, probably harbouring a massive black hole. It is also, from a number of accounts, very similar in structure (barred spiral) and size to our own Milky Way Galaxy, except that our galaxy has a much quieter nucleus. It was discovered by James Dunlop, a Scottish astronomer,  from Australia in 1826. A very good description of this galaxy can be found at www.robgendlerastropics.com/NGC4945text.html 

The little galaxy above 4945 is 15.3 magnitude PGC 45317. (PGC stands for Principle Galaxies Catalogue).

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M20, popularly known as the Trifid Nebula, is a 6.3 magnitude red emission nebula located roughly (estimates vary from 2200 to 9000) 6000 light years away in Sagittarius. The bright stars at centre of the tri-lobed nebula are part of a triple system with an overall magnitude of 7. The brightest component of the triple system is a massive O-type supergiant. These stars excite the gas of the nebula making it glow red. The nebula is entirely surrounded by a blue reflection nebula, which is most prominent at the northern end (left hand side), and which is in turn illuminated by another supergiant, also about magnitude 7, nicely located at the centre of the blue nebulosity. The system was discovered by Charles Messier in 1764.

Of interest is a jet emanating from the bright rim of rounded globule at the lower right hand side of the red emission nebula. The start of this jet, which points to the left, is just visible in the image.

The image is an LRGB composite, with exposures (L:R:G:B) = 70:45:45:65, and taken in late August/beginning September with my SBIG ST8-XME/CFW-8 camera and filter wheel. The exposures were kept relatively long to ensure as little noise as possible but resulted in terrible blooming of the brightest stars, particularly the one at top left. I therefore layered earlier shorter exposures of just the stars taken with my original ST7 in 2006 over the damage caused by the blooming, and with a little more cosmetic cleanup, produced stars that are not particularly un-pleasing. Image reduction and a little Richardson-Lucy deconvolution was done with CCDSoft, and all further processing and a little more sharpening done with CS2.

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