Celestial hemisphere:  Northern  ·  Constellation: Cygnus (Cyg)  ·  Contains:  NGC 6871  ·  The star 27Cyg
Sh2-101 - Tulip Nebula, Walter Koprolin
Sh2-101 - Tulip Nebula
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Sh2-101 - Tulip Nebula, Walter Koprolin
Sh2-101 - Tulip Nebula
Powered byPixInsight

Equipment

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Acquisition details

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Description

I acquired the narrow-band data during 5 different nights at 3 different locations. I got 7.3 hours of usable Hα data, but only 4.5 hours of [OIII], and only 20 minutes of [SII] because of incoming clouds. So I decided to skip the [SII] data altogether. [OIII] data was very noisy, but usable for creating a tone map. The Hα data was not uniform because of different sky conditions and different framing in individual nights, the left part of the image actually got 2 hours more of dark-sky Hα exposure than the right part.

Processing steps: Basic data reduction, registration and combination, background flattening, noise reduction, deconvolution, non-linearization, star-background separation, local contrast enhancement, star size reduction, color synthesis using tone mapping, color correction, re-adding of the stars.

Tonemap composition:

Red = Hα

Green = [OIII]

Blue = [OIII] + 15% Hα to compensate for missing Hβ

Master Luminance composition:

L = Hα + 24% [OIII]

Some color-tweaking was required after tone mapping because the result was way too greenish.

Sidenote on colors: Tone mapping exaggerates the green-blueish [OIII] contribution. Red Hα has about 10x more intensity in the Tulip Nebula than [OIII], as I measured it. So, in "camera reality", the nebula should look totally red. But then again, the human eye is not very sensitive to Hα, but much more so to [OIII] and Hβ. So maybe the color scheme is not that far off from what the human eye would see if the nebula was bright enough.

Comments

Sky plot

Sky plot

Histogram

Sh2-101 - Tulip Nebula, Walter Koprolin