M42 – The Great Orion Nebula!

M42 is one of the most well-known, brightest and most imaged targets out there! It's a large diffuse nebula situated in the milky way, in the famous constellation of Orion. M42 is so bright in fact, it can be seen with your own eyes in a dark enough place. This object is not small, it's a massive 24 light years across with an estimated mass that of 2,000 suns!

Acquisition:

18 x 10min, gain 139 offset 50

12 x 30sec, gain 139 offset 50

20 x 5sec, gain 139 offset 50

Dither on all frames

45 darks

Equipment:

HEQ5 Pro

WO Z73

ZWO ASI1600MM

Astronomik 6nm 1.25" Ha Filter

Pre-processing:

Checked for bad frames in Blink, registered and stacked in Deep sky stacker using kappa sigma clipping

Processing:

Processing mostly done in Pixinsight. First I combined three images, a stack of 10 minute exposures, 30 second exposures and 5 second exposures using the HDRComposition tool. This gives the image a higher dynamic range to work on the blown-out core. Cropped the image to get rid of artefacts from the dithering. Then used MultiscaleLinearTransform for reducing the noise in the linear stage. DBE for extracting the background, which was particularly difficult to get right with all the nebulosity everywhere! Histogram transformation tool used to stretch the image, going into the non-linear phase. HDRMultiscaleTransform tool used to bring out the core detail, also making the stars visible in the trapezium. Then I applied ACDNR to further reduce the noise and smooth out the dust lanes using a range mask. I created a clone of the image to use as a luminance mask, where I applied local histogram equalisation for bringing out more detail in the nebula and surrounding dust. I then created another range mask, used for bringing out the dust and darkening the background. This was done in multiple iterations to get it right. I used more iterations of curves adjustments and local histogram equalisation to further enhance the detail. Then I sharpened up the core. Then I took the image into Photoshop CS2 and ran some astronomy actions. Make stars smaller was applied to reduce the star size further, making the eyes more drawn to the dust as opposed to the stars. Less crunchy more fuzzy helps to give the image a more 3D feel, so it isn’t flat looking. Local contrast enhancement particularly helped the region between Orion and running man. Finally, I saved the image and rotated it to my liking.