The constellation of Orion photographed in deep red Hydrogen-Alpha light and rendered in monochrome. The filtered view brings out the very faint nebulosity in and around Orion, most invisible to the eye. The Belt of Orion is just below centre, with the region of the Horsehead Nebula below the left star of the Belt, Alnitak. Below it is the very bright Orion Nebula. Surrounding the left side of Orion is the arc of Barnard’s Loop, now thought to be a supernova remnant. The large circular nebula around Orion’s head is the Lambda Orionis Nebula or Sharpless 2-264. At left in Monoceros is the bright Rosette Nebula, NGC 2237, and above it the fainter nebulosity Sharpless 2-273 around the Cone Nebula. The small patch at top is Lower’s Nebula, Sharpless 2-261. Betelgeuse, at a record dim magnitude visually at this time, here looks more normal in brightness, at least brighter than Bellatrix at right, as seen here in red light, as Betelgeuse is a red giant star. I shot this using an Astronomik 12nm clip-in H-alpha filter on the Canon EOS Ra camera, a factory-modified red-sensitive mirrorless camera designed to pick up more of this deep red H-a nebulosity than can a normal camera. As the original image is simply deep red, it is best rendered as a monochrome image. However, this could be combined with colour images to make an enhanced full-colour image. This is a stack of 9 x 8-minute exposures at f/2.2 with the Sigma 50mm lens and Canon EOS Ra at ISO 1600, on the iOptron Sky Guider Pro tracker. Taken before moonrise on February 12, 2020. Stacked, registered and blended with Photoshop 2020. Nik Silver EFX selenium and Luminar Flex Soft Glow filters added for artistic effect, to add a soft blue glow to the image, not red. The temperature was about -15° C this night with a fine chill wind!
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!
