Orpington Astronomical Society

Astronomy => Astrophotography => Topic started by: MarkS on Dec 16, 2021, 10:35:39

Title: Rosette Nebula and surrounding dust
Post by: MarkS on Dec 16, 2021, 10:35:39
Here's the Rosette Nebula taken with my unmodified Canon EOS R mirrorless camera:

(http://www.markshelley.co.uk/Astronomy/2021/Rosette_EOSR_20211210_smaller.jpg)

Larger version can be found on Astrobin: https://www.astrobin.com/byyxnq/

This was colorimetrically processed to preserve the both the natural colour and to show the large area of interstellar dust that surrounds the nebulosity.

Acquisition details are the following:

    * Unmodified Canon EOS R on Takahashi Epsilon 180ED on Skywatcher EQ6 Pro mount
    * 80 x 2min dithered exposures at ISO 1600
    * SQM sky quality reading averaged 20.7 during the imaging session (i.e. Bortle 4)

Colorimetric processing in PixInsight with the following main steps:

    * Bayer Drizzle in PixInsight after calibration with darks, flats and bias frames
    * Noise reduction
    * Apply daylight white balance and colour correction matrix (both from DxOMark) to linear sRGB colour space (i.e. gamma = 1.0)
    * DynamicBackgroundExtraction (i.e. subtraction of light pollution)
    * ArcsinhStretch
    * Apply the variable gamma curve for the sRGB colour space

Note that the non-linear steps (i.e. arcsinh stretch and colour space gamma) are the final steps.  This is important for consistent colour throughout the whole dynamic range.

Mark
Title: Re: Rosette Nebula and surrounding dust
Post by: Carole on Dec 16, 2021, 17:51:40
That's really good for an unmodified DSLR camera, albeit a special one.

Carole
Title: Re: Rosette Nebula and surrounding dust
Post by: MarkS on Dec 16, 2021, 21:25:50
Quote from: Carole
That's really good for an unmodified DSLR camera, albeit a special one.

Thanks.  As long as you choose carefully, modern consumer cameras will give very similar results to dedicated OSC (one-shot-colour) astro-cameras but for a much cheaper price.  In some cases the identical sensor is used.  But consumer cameras have internal filters to tailor their response to match human vision, so they have reduced sensitivity to H-alpha.  Right now, I'm going through a phase where I actually prefer this "natural colour".

Mark