March 2015


The Trifid Nebula

M20 - the Trifid Nebula


Image of the Month: The Trifid Nebula

Image copyright: Andre Potgieter


This image of the Trifid Nebula was taken by Andre Potgieter from a backyard in Uitenhage. It has a cumulative exposure length of 9.3 hours and was captured with an inexpensive DSLR camera.

The Trifid, catalogued as M20 and NGC 6514, is a region of molecular hydrogen in the constellation Sagittarius.  It’s distance has not been well established, but it lies somewhere between 2200 and 7600 light years away.  This particular cloud of dust and gas can be seen from Earth as both an emission nebula and a reflection nebula.  A young cluster of stars in the pink part of the region have just been born, and shine hotly in blue and ultraviolet light, which energises the surrounding gas.  The gas glows with a characteristic red colour, common to all such regions.  But other parts of the cloud are too far from the new stars to be energised in this way, and merely reflect the starlight back towards us.  The size of the molecules and dust particles reflect blue light more than red, which gives reflection nebulae their characteristic blue colour.

The nebula gets its name from the arrangement of dark lanes snaking through the region.  Through the eyepiece, three major lanes branch out from each other in the centre, hence “Trifid”.


June /July 2014
Trifid Nebula
171 Light Frames - 112 Used - 59 Discarded Due To LP
9.3 Hours Exposure - 121 x 5Min ,@ ISO 800
60 x Dark's , 50 Flat, 50 Bias - Canon 1100D
SW200P , OAG , EQ6 Mount
Astro Photography Tools For Camera Control.


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