A mosaic of the Sword and Belt region of Orion the Hunter, showing the diverse array of colourful nebulas in the area, including: curving Barnard’s Loop, the Horsehead Nebula below the left star of the Belt, Alnitak, and the Orion Nebula itself as the bright region in the Sword. Also in the field are numerous faint blue reflection nebulas. The reflection nebula M78 is at top embedded in a dark nebula, and the pinkish NGC 2024 or Flame Nebula is above Alnitak. The bright orange-red star at far right is W Orionis, a type M4 long-period variable star. This is a 4-panel mosaic with each panel made of 5 x 2.5-minute exposures with the 135mm Canon L-series telephoto wide open at f/2 and the filter-modified Canon 5D MkII at ISO 1250. The night was somewhat hazy which added natural glows on the stars. No filter was employed here. The camera was on the iOptron Sky-Tracker for tracking but no guiding. Shot from outside Quailway Cottage near Portal, Arizona, Dec 7, 2015. All stacking and stitching performed in Photoshop CC 2015. Stacking done with median combine stack mode to eliminate geosat trails through the fields.
The Orion Nebula, M42, with its companion nebula M43 to the north, and the blue Running Man Nebula at top (aka NGC 1975), all in a clear but moonlit sky, illuminated by a first quarter Moon, making the sky blue. So this can’t be a very deep image, but it shows the main features visible in a large telescope. The loose open cluster, NGC 1981, is at top — I should have framed this scene a little more north to better include the cluster. This is a blend, using luminosity masks, of three sets of exposures: 8 x 8 minutes for the main image content + 4 x 2 minutes for a mid-level exposure for the core area + 1 x 30-second for the Trapezium area right at the core. This sort of “high dynamic range” blending is necessary for M42 as it contains such a range of brightness that no single exposure can record it all. However, I did not use HDR methods to do the blending, but luminosity masks which are easy to make with one click in Photoshop — Command/Control click on the RGB Channel image — and they allow far greater control of the blending. This sort of exposure blending is needed because while your telescope-aided eye can see the faintest tendrils and the bright quadruple star system, the Trapezium, at the centre with no problem, cameras cannot. At least not in a single exposure. All were with the Astro-Physics Traveler apo refractor at f/6 with the Hotech field flattener and Nikon D750 (not modified) at ISO 200!
The Orion Nebula, aka Messier 42, at centre, with the blue Running Man Nebula (NGC 1973-5-7) above it. The smaller nebula attached to the top edge of M42 is M43. The blue star cluster at top above the Running Man is NGC 1981; the loose star cluster below M42 is NGC 1980. This is a stack of 8 x 5-minute exposures with the Canon EOS Ra mirrorless camera at ISO 800 unfiltered, blended with a stack of 6 x 8-minute exposures at ISO 1600 but through the dual-band Optolong L-Enhance filter that records the faint red nebulosity very well. Blending and masking the filtered with the unfiltered shots allows the faint red nebulosity to come through while retaining the blues, magentas and even subtle greens of the bright nebulosity and the blue of the hot stars as recorded by the “white-light” images. These two sets of long exposures are blended using luminosity masks with a set of 6 x 60-second exposures and 4 x 30-second exposures, both at ISO 400, for recording the bright core of M42 with its Trapezium stars that would otherwise be overexposed into a bright mass with only long exposures. The short exposures were all unfiltered. I applied a high-pass sharpening filter to snap up contrast in the dark lanes. All were through the SharpStar HNT150 Hyperbolic Newtonian Astrograph at its native fast focal ratio of f/2.8. for a focal length of 420mm. Taken from home January 28, 2020. All stacked, aligned and blended in Photoshop 2020. PS’s Auto-Align function aligned all 24 images in one fell swoop in less than a minute.
