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M33 LRGB, 





    
        

            rhedden

M33 LRGB

Technical card

Resolution: 3291x2514

Dates:Nov. 22, 2014Jan. 15, 2015

Frames:
Baader Planetarium LRGB 36mm: 15x450" bin 1x1
Baader Planetarium LRGB 36mm: 83x100" bin 3x3

Integration: 4.2 hours

Avg. Moon age: 26.82 days

Avg. Moon phase: 14.77%

Bortle Dark-Sky Scale: 3.00

Astrometry.net job: 925831

Locations: Muleshoe National Wildlife Refuge, Muleshoe, TX, United States

Description

M33 imaged at f/7 through the C11 Edge with focal reducer. RGB frames were taken on a very windy night with poor seeing, and luminance was taken on a still night with very good seeing. The corners of the image are clipped due to some camera rotation between the two nights, but it was so cold on the second night that I couldn't do anything about it with my frozen fingers.

Processing workflow for "B" revision (mostly freeware):

1) Luminance stack was stretched in Deep Sky Stacker, taking care not to clip the sky background or burn out the highlights. Saved as a 16 bit TIFF file (apply adjustments).

2) Noiseware Pro Edition was used to filter luminance noise (30%, gentle noise reduction) and the result was saved as a TIFF file.

3) The luminance TIFF was opened in Astra Image and multi-level wavelet sharpening was applied to obtain the final luminance image. At this stage, background levels were still quite high; reduced background in GIMP later.

4) R, G, and B stacks were combined into an RGB file in IRIS. Saved as a fit file with no further processing.

5) The RGB fit file was opened in Deep Sky Stacker and stretched. R, G, and B histograms were aligned and colors were balanced in Deep Sky Stacker. Saved as a TIFF file (apply adjustments).

6) The RGB TIFF image was opened in IrfanView, and the saturation was pumped up to the highest level I was comfortable with.

7) Noiseware Pro Edition was used to filter chrominance noise (80%, aggressive, basically a blurring operation). Saved as a TIFF file. I spent $50 on this software because it just works so well- everything else in the workflow is freeware.

8) The RGB image was opened in GIMP 2.9 (16 bit beta version) and adjustments were made to colors using the Curves function. A small burned out (overexposed) area in the brightest H-alpha region was "repaired" using the color picker and airbrush tools (cheating!!!!).

9) LRGB combination was done in GIMP 2.9 using Layers with RGB on top and luminance on the bottom; RGB layer was set to Color (HSV) mode and luminance layer was set to Normal mode.

10) Slight gradients in luminance and colors were removed in GIMP 2.9 using Blend tool. This is a long series of steps that takes some skill.

11) Colors and curves were re-adjusted several times in GIMP to obtain the final image, which was exported as a jpg file.

Comments

Author

rhedden
rhedden
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Revisions

  • M33 LRGB, 





    
        

            rhedden
    Original
  • Final
    M33 LRGB, 





    
        

            rhedden
    B

Histogram

M33 LRGB, 





    
        

            rhedden

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