ngc 2244 rosette nebula in SHO

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it’s time to update my version of the rosette nebula for 2021. this was one of the first targets I captured after astromodifying my DSLR last year. I had a series of before and after and it was obvious the astro-mod was worthwhile. However, I’ve been getting such detailed images with my cooled mono camera with filters that I’ve been looking forward to seeing a big update for this year.

I was able to capture about 14 hours of data across Ha, Sii, and Oiii narrowband channels. However, upon inspection, I had to toss a third of the Oiii data due to running into the treeline in early morning hours.

a second change this year was in the PixInsight processing. the key difference in processing was to create a luminance layer out of the Ha data and apply that to SHO mapped RGB starless image. I’ll show a few of the key steps below, but first the imaging session details:

imaging session details:

imaging cameraZWO ASI 1600MM Pro
guide cameraZWO ASI290mm Mini
mountSkywatcher EQ6-R pro
telescopeExplore Scientific ED102 APO
flattener/reducerHotech 2″ self centering flattener
exposure settingsgain 139
exposure 180s
stacking90 lights – Optolong 7nm Ha
90 lights – Optolong 6.5nm Sii
60 lights – Optolong 6.5nm Oiii

additional calibration for each channel
60 darks
60 flats
60 dark flats
astrobin link
imaging session details.

processing notes:

I’ve mentioned the general flow above, but share a few key steps along the way for reference:

the 3 channels are processed individually in linear state as usual with DBE and light multiscale linear transformation noise reduction:

Next, the 3 channels are masked and boosted with exponential transformation before going non-linear.

Now that the 3 channels are stretched to non-linear with histogram transformation, the stars are removed with Starnet.

the starless non-linear channels are combined using pixelmath to form the starting point for the SHO mapped RGB image processing:

ngc 2244 starless RGB image mapped in SHO

Finally after several more detailed processing steps to further reduce noise and some light sharpening around the structures the stars are brought back in by applying the Ha as a luminance layer via LRGBCombination:

ngc 2244 in SHO after applying LRGB combination to bring back the stars in the luminance

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