Southern Cross and Coalsack in Ha-RGB - reprocessed with Continuum-Subtraction (Rolf Dietrich)

Celestial hemisphere: Southern · Constellation: Crux (Cru) · Contains: Mimosa (βCru) · The constellation Crux (Cru) · The star Becrux · The star Gacrux (γCru) · The star α1Cru · The star α2Cru · The star δCru · The star εCru · The star ζCru · The star ηCru · The star θ1Cru · The star μ1Cru

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Southern Cross and Coalsack in Ha-RGB - reprocessed with Continuum-Subtraction

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Southern Cross and Coalsack in Ha-RGB - reprocessed with Continuum-Subtraction

I took the image of the Coalsack in July 2018 in Namibia on the beautiful Astrofarm Kiripotib. Due to the strong continuum radiation of the Milky Way, despite the very narrow Ha filter (3.5nm), Ha was also simulated in places where there were actually no Ha emissions.
Now I have tried a continuum subtraction with the existing red frames.
For comparison look - VERSION B - my old image, processed in 2018 without continuum-subtraction.
I think the difference can be seen clearly and corresponds more to reality.
In the meantime, of course, I've also learned something about image processing🙂 .

I hope you like the image.

My workflow in short:
Subtract the red frame from the Ha-sum frame. As a result, the stars were "radically" removed and instead "black holes" remained which were then filled in again with the RGB stars.
I also tried starless pictures, but the result was less convincing.

Thanks to Frank Sackenheim, our overseer in Kiripotib in July 2018 who pointed out to me the possibility of a continuum subtraction.

Classically for Ha continuum-subtraction another (expensive) narrow-band filter is used which selects the frequency next to Ha.
This continuum filter has the same bandwidth as the Ha filter.
This gives an even cleaner differentiation.
The disadvantage is that you have to invest additional exposure time.

Final
Original
B

B

Description: without continuum-subtraction

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Southern Hemisphere Astro

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Southern Cross and Coalsack in Ha-RGB - reprocessed with Continuum-Subtraction

Southern Cross and Coalsack in Ha-RGB - reprocessed with Continuum-Subtraction

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Southern Cross and Coalsack in Ha-RGB - reprocessed with Continuum-Subtraction

Southern Cross and Coalsack in Ha-RGB - reprocessed with Continuum-Subtraction

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