Harry sketches one of the favourite objects in the Australian summer sky – the Great Nebula in Orion
The Great Nebula in Orion, sketch by Harry Roberts
Like most amateurs perhaps, my first view of a nebula was M42 in Orion. In our summer skies the hero’s sword hangs upwards from his belt, and in 1962 a school friend showed me the “sword’s” central star with his 4” reflector. Back then Adelaide streetlights went off at midnight (truly) – and the sky was dark. The impact of seeing the “Great Nebula” for the first time is with me still, and recalls summer holidays of years ago.
For “sky sketchers” M42 is a big task – it‘s very large, with much complex detail, and has a huge brightness range. A while back a friend suggested an attempt on the nebula in pencil, with a series of images recording it in parts. Recently I made a start on the “Orion Project” from my backyard, to be augmented later from darker sites. Before starting I compiled a chart of the main background stars from astro-maps to save observing time The ten inch “dob” and the C8 were both used with the 14mm Radian eye piece – and surprisingly the static image in the C8 at 140x gave the best view. And what a view it was: the sky was surprisingly good with nearby trees enhancing the darkness.
Theta 1 Orionis, “The Trapezium”, was clearly seen as six stars, each brilliant and steady, with 10.5 mag. components E and F bright specks well clear of the four main stars. They all seemed to sit in a darker patch of the main nebula – perhaps a contrast effect. Theta 2 Orionis just to the SE with its two bright neighbours formed a line pointing almost due east. The background of the Great Nebula was peppered with small stars to <11 mag. i set to with pencil and blender map as much of the nebula possible over about 2½ hours, adding notes on brightness, detail sketches etc.
e. e. barnard saw m42 “resembling a great ghostly bat” in yerkes refractor, barnard’s “bat” loomed bright north side – being only truly dark part whole field all rest was luminous greater or lesser extent, it soon clear that my chart covered brighter half nebula! very nebulous star v372 marks southern edge sketch but is fact centre vast nebula.
apart from “bat’s” wings head (also called “fishes mouth”), there another smaller feature looked black. this column seemed occult inner region 1.5’ sw trapezium, maybe faint dust tail blowing away southwards; while i’ve viewed many times i’d never seen dusty feature! perhaps object one cooler “trunk-like structures” sustained light-years by magnetic fields some research suggests. easier see than most others in, say, “eagle nebula” m16, eta carina nebula.
there too record, outer parts are sketched brief. within its brightest contains incredible will tackle future sessions 4.8 nagler (x400), oiii h? filters well none were used for first sketch.
enjoy summer sky.
Harry Roberts, Sun and Moon observer and member of the Sydney City Skywatchers