M27 Dumbell

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Hi Everyone,


I would like some help with this one too please!

Scope: 0.5M Classical Cassegrain 4.7M focal length.
Mount: ASA DDM85 Premium
Camera: FLI PL16803
LRGB

Taken at Savannah Skies.

larger file here: https://www.sendspace.com/file/z8ftx4 1.7 MB.

Acquisition with CCDAutoPilot5, Maxim, FocusMax

Processing: CCDStack, G2V star colour balance, Photoshop and PixInsight.

Unlike many renditions, I seem not to have a greenish Dumbell, but after doing a careful G2V star colour calibration, I thought I kept the RGB balance throughout the processing from the linear through the non-linear processing.....I see some greenish star fringes....I wonder what you would suggest for this issue...?? I have tried doing a minimum filter on the green channel, but this caused red blue fringes even with less than 1 pixel of minimum filter (fade). I was wondering about trying a small degree of morphological transformation on the green data stars in PI....

Suggestions welcome, thanks !!

Tim

[peter_4059 (Peter)]

That's got a heap of detail including some faint outer wisps showing. Thanks for sharing.

[RickS (Rick)]

Nice job, Tim.

I found G2V calibration wasn't that helpful since conditions change from night to night and don't affect the filters equally. I also experimented with eXcalibrator which I found a bit better. In the end I've not found a single method that always works reliably.

Wrt star colour fringes, a useful technique is to apply a star mask and blur the chrominance. You may need to boost saturation of the stars again afterwards. In PI you can achieve the blurring with MultiscaleMedianTransform. Just remove the bottom few layers and make sure you set Target to Chrominance.

Cheers,
Rick.

[gregbradley]

Another fantastic image Tim. You are really productive. They are all at a very high standard.

Another approach to a colour fringe with stars is to match the star sizes better before colour combine using decon on the filtered image that has enlarged stars. Seeing varies, wind, tracking variations, high cloud can all mean one set may have slightlt larger stars than the others.

Also double check your registration. I have had it happen occasionally where some subs refuse to register accurately. That's when I nuke them with Registar! Resistance then is futile and they align. Hehehe

Greg

[topheart]

Thanks very much Rick, Peter, and Greg. I will try those suggestions! Thanks!

Tim

[LewisM]

M27 was the very first astro-image I EVER took. I must do it properly one of these days.