A New Year's Eve Balloon?!

[Howard]

Hello:

Here's a rendition of the Bubble Nebula, captured last summer, and only finally processed over the past few days.

Since New Year's Eve is only days away, I thought it might be fun to compose the frame so that the bubble might instead be imagined as a balloon, having just escaped the grasp of a reveller, and now seen drifting up and away into the clouds !

Processing was done entirely with PixInsight, except for use of CCDInspector to evaluate subexposures and to monitor overall specs during processing. Processing details follow.

One particular challenge was to blend the binned Halpha channel into the unbinned luminance, without compromising the underlying resolution of the luminance - I had no good ideas for how to do that, though a straight upsample of the Halpha gave a blended LHa with about the same average FWHM as the pure L. Another difficulty was getting a "realistic" colour balance in a field that is almost filled by the strong Halpha emission: Vicent's formula - and tutoring by Harry - were essential, and hopefully worked well despite being by a used by noob .

Thanks for looking. Comments and suggestions much appreciated .

Image capture details
Telescope: PlaneWave CDK17, with a focal reducer at f/4.5.
Mount: Paramount ME.
Camera: SBIG STL-4020M.
Exposures: Approximately 12 hours total: about 300 minutes luminance unbinned, and 100 minutes in each of red, green, blue, and Halpha, all with 2x2 binning; 10 minute sub-exposures in all channels.
Flat field correction: using twilight flats.
Image capture: TheSkyX, MaxIm DL, FocusMax.
Image scales: Unbinned pixel size 0.78", frame about 25' on a side.
Imaged on three nights in summer 2011 from rural British Columbia, Canada.

PixInsight processsing highlights
LUMINANCE:
Blended Luminance-Halpha (LHa) composite made with Vicent's formula - and tutoring by Harry ; Deconvolution (reduced Aspect ratio and nonzero Rotation to correct for guiding problems on gusty nights); MultiscaleMedianTransform to reduce noise on first two layers; Two applications of HDRMultiscaleTransform, to 6 layers and then 3 layers, with stars masked; MorphologicalTransformations applied separately to small and bright stars (2-way selections to circularize and erode), followed by mild UnsharpMasks; CurvesTransformation to reduce bright star halos; CurvesTransformation to improve contrast on the bubble edge and the most textured part of the nearby nebula, using two "custom" masks; Very mild UnsharpMask to entire image.
CHROMINANCE:
GradientsMergeMosaic used to combine two Halpha sets with different framing (consequence of finding a suitable auto-guide star before/after meridian flip); Blended Red-Halpha (RHa) composite using Vicent's formula; RHaGB ChannelCombination, BackgroundNeutralization, and ColorCalibration; L* channel of RHaGB matched to LHa using LinearFit; LRGBCombine (default Lightness=Saturation=0.5); FastRotation and DynamicCrop to position the bubble slightly up and right of image centre, and in a suggestive orientation ; Histograms and CurvesTransformations for mild final blackpoint, contrast, and saturation adjustments.

[Lex]

Howard,

wow your rendition of the Bubble Nebula is absolutely awesome!
Everything is nice in there, starshape, color, background balance, no noise!! A picture for the contest poll man!!! 

Nice!!!

[Howard]

Hi Lex:

Thank you so much for the appreciation !

The new MultiscaleMedianTransform and HDRMultiscaleTransform tools are amazing, and their impact was huge, along Vicent's Halpha blending formula, so simple to use and, like many great ideas, almost obvious - but only in retrospect !

Howard.

[Jules]

A lovely image Howard, happy New Year to you!

Best Regards

Julian

[Howard]

Hi Julian:

I'm just climbing out of a hole at work, and want to finally catch up with a thank you for your kind message, and to wish you too a (belated) Happy New Year!

Next stop on my to do list is to congratulate you on your image of the Horsehead - on your post, there in a minute .

Howard.