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The annual Orionid meteor shower peaks around October 21 with meteors appearing to radiate from the northern part of the constellation of Orion. The winter Milky Way and the Orion Arm, where the Solar System is located, is very colorful with many hydrogen emission nebulae, blue reflection nebulae, star clusters, orange interstellar dust and colorful stars--hot blue stars to cool ruby red stars. This image was made with a stock digital camera and processed to bring out the wonderful colors in the region.
The galactic plane of the Milky Way runs from top center to lower left. The Orion spur goes off to the right from the galactic plane. An index to some of the objects in the scene is in the diagram below. Stars to about magnitude 17 were recorded.
Technical. This image is a 7-frame mosaic, made from 220 images, obtained with a Canon EOS 6D Mark II DSLR Camera and Sigma 105mm f/1.4 DG HSM Art Lens at f/1.4 and ISO 1600, 30 second exposures and many exposure stacked at each mosaic position. No dark frame subtraction, no flat fields. Tracking with a Fornax Lightrack II and no guiding. The mosaic was made in portrait orientation with 3 frames on the top row and 4 frames on the bottom row.
Top row, left to right: 25 frames (12.5 minutes), 23 frames (11.5 minutes), 16 frames (8 minutes).
Bottom row, left to right: 22 frames (11 minutes), 30 frames (15 minutes), 61 frames (30.5 minutes), 22 frames (11 minutes). The 61-frame position was centered on the constellation Orion, and short exposures were made for the bright M42 region: 7 frames at 8 seconds, 8 frames at 3 seconds and 6 frames at 1 second were stacked.
The total exposure was 100.9 minutes. The full resolution image plate scale is 11.2 arc-seconds per pixel.
Post processing: Raw conversion with Rawtherapee with settings tuned for astrophotos, including maintaining star color in saturated stars. Rawtherapee processing settings described here. Output color space was Rec.2020 to match the future of high dynamic range TVs. Look for a future article on this topic. Stretched with rnc-color-stretch. Also see Astrophotography Image Processing Basic Work Flow.
This is a natural color image. The high dynamic range of astrophotos must be stretched to bring out the range of details the camera recorded. But the typical image stretch process loses color for brighter subjects (e.g. stars and the brighter parts of deep sky objects become whiter as they are made brighter). This image uses a new algorithm that does not lose color during the stretch. The new algorithm enables fainter details to be shown and with less noise. Learn about the new software and download it free (open source) here: rnc-color-stretch. Accurate color at the low end depends on accurately subtracting airglow and light pollution. On this night, the airglow was very high, and the amount and color of the airglow was changing rapidly, and varied significantly between frames. This made assembling the mosaic difficult.
The Exposure Factors, CEF, CEFA are measures of the relative amounts of light received from a subject. It can be used to fairly compare wildly different lens/telescope apertures and exposure times. For this image:
Modern DSLRs like the 6D Mark II include on sensor dark current suppression and low fixed pattern noise at ISOs around 1600 and higher, making no need for dark frame subtraction. Modern raw converters correct for light fall-off and also correct for hot/dead/stuck pixels. This makes processing low light images easy: simply align and average.
To learn how to obtain stunning images like this, please visit my Extensive Articles on Photography .
Keywords to this image = astrophoto-1 meteor Messier nebula comet night low-light digital_astro canon_6D2
Image ID: orion-105mm-7pos-mosaic-rs20-rs12,sc1.c10.20.2018.h-1400vs.jpg
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Last updated June 05, 2023