Observation by David Davies: M1, The Crab Nebula

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David Davies


David Davies


2022 Mar 07 - 22:01


2022 Mar 15 - 13:09


The Crab Nebula (M1)

  • 8-inch Ritchey-Chretien
  • Skywatcher EQ8 mount
  • QSI 683 camera

25 x 5-min lum, 15 x 5-min RGB


Cambridge, UK

Target name

M1, The Crab Nebula


M1, The Crab Nebula

About this image

I've returned to the Crab Nebula as part of understanding the imaging differences between my one-shot ASI 294MC Pro camera and my QSI 683 mono camera with Astrodon filters.

The 294 camera produces a pleasing image, but the HII regions are very weak and rendered orange rather than red. I suspect that this is due to the green pixels having significant sensitivity at the red end of the spectrum and capture these HII regions as being partly green in colour. Hence the 'orange' rendering of the HII red.

By contrast, the HII tracks are rendered red in this image as the Astrodon filters have very sharp cut-offs between the colours.

I think the Crab Nebula is a tricky target. Although it is quite bright, it is relatively large, so the surface brightness is low. So you need lots of data to bring out the detail.

I was plagued by hazy skies and the luminance data, in particular, was barely useable. Nonetheless, it is quite a pleasing image, and I've tried to hold back the temptation to pop up the colours. The presented image is very much how it came out of PixInsight's Photometric Colour Calibration tool.


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