California Nebula, Sh2-220, NGC1499 (Alastairmk)

California Nebula, Sh2-220, NGC1499

This is a narrowband image of the California Nebula in Perseus taken over 7 nights in October 2022. I was ruthless in rejecting subframes that did not meet FWHM and eccentricity standards, and my first attempt with the Normalized Scale Gradients script eliminates a few more with stubborn light pollution and thin cloud gradients. Of the 209 subs rejected on visual inspection (tree branches, morning skies, passing clouds, crazy tracking), only 175 made the final grade, for an integration time of 23.3 hours. My aim was to capture as much of the detail and wispy dust clouds as possible. While there was good Ha/NII and SII data, the OII signal was very faint and it was an effort to separate this from the LED light pollution in the area of my observatory to get the rich blue nebulosity.

The integrated masters were processed using starless tone maps and I spent a lot of time stretching with the new GeneralizedHyperbolicStretch process in Pixinsight and I'm still far from mastering this, even though the outcome was OK by my standards. RGB stars were added at the end with Pixelmath based on 3x25 60s exposures through RGB filters.

Original
Final
C

C

Description: The revised image follows a discussion with a fellow member of the Northern Virginia Astronomy Club (NOVAC) who kindly guided me through a systematic approach to using GeneralizedHyperbolicStretch (GHS) on my data. This helped me a lot to preserve the rainbow color effect and to preserve some of the detail like the "flying bat" in the red area, as well as the cobalt blue hues. I then sharpened the image with MLT (6 layers) and TGVDenoise to aggressively reduce chrominance noise, although some of the limitations of the limited dynamic range of my camera are still lingering in the background.

Following my colleague's advice, I also used GHS to stretch the RGB stars and to eliminate the background. Stars were added using Pixelmath using the inverse of the product of the inverses approach.

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NOVAC
Light Polluted skies

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Backyard
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Own remote observatory
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Mix of multiple sources
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Status	Basic success
Started	...
Astrometry.net job	6789605
PixInsight job	n/a
PixInsight queue size	n/a
PixInsight stage	n/a

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California Nebula, Sh2-220, NGC1499

California Nebula, Sh2-220, NGC1499

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California Nebula, Sh2-220, NGC1499

California Nebula, Sh2-220, NGC1499

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