The Seagull Nebula in Ha-OIII (Jim Lindelien)

The Seagull Nebula in Ha-OIII

The Seagull Nebula in bi-color Ha-OIII (HOO).

A comment about workflow for the technically curious:

Rather than treating the OSC data as a color image to be de-Bayered with the VNG algorithm--which would have caused Ha and OIII signal crosstalk too early in the processing workflow--I instead conceptualized the Bayer sensor as four interleaved but independent mono cameras and used PixInsight's SplitCFA process to make cleaner separations of the Ha signal contained in the red CFA pixels, and a 3x deeper stack (for better SNR) of the dimmer OIII data by summing together the two green plus the blue CFA pixels. Thus, this is a kind of hybrid binning.

Atmospheric turbulence convolves photons across neighboring pixels regardless. Dithering the sub exposures plus 2x drizzle integration of the stacks restored much of the original sensor resolution to these channels despite their interleaved nature in this hybrid binning strategy. Given all the above, with regard to the signals' spatial frequencies along the X and Y axes, the Nyquest Sampling Theorem is respected and so an acceptable image can result.

Versus a monochrome camera, of course, per unit time less silicon is exposed to each signal channel and there is inefficient double filtering of the photons through the sandwich of NB and RGB filters, which degrades SNR, but this object is bright, and not much imaging time is needed to overcome such inefficiencies.

Thereafter the HOO post processing proceeds just as it does if Ha and OIII were imaged separately on a normal monochrome sensor camera.

Comments are closed.

Final
Original
B

B

Description: Portrait version--after you open the square thumbnail--and intentionally mirrored. I've left the other version as Final for PC viewing but this one's my personal preference as it strikes me as the more dramatic presentation even though the data are identical.

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Status	Advanced success
Started	...
Astrometry.net job	4361979
PixInsight job	UQ8G9RXODVTX8NISLU4U4ZHON9HPS6CS
PixInsight queue size	n/a
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RA (center)	07h09m36s.71
RA (top/left)	07h14m30s.76
RA (top/right)	06h55m16s.38
RA (bottom/right)	07h04m36s.32
RA (bottom/left)	07h23m56s.72

Dec (center)	-10°45′40″.3
Dec (top/left)	-07°26′59″.9
Dec (top/right)	-10°54′35″.3
Dec (bottom/right)	-14°04′14″.9
Dec (bottom/left)	-10°34′22″.9

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