NGC6744 - Learning LRGB

[Doogs38]

Hi Folks. My LRGB learning continues and this time I've attempted another galaxy, NGC6744. I've finally found a way to produce better and more saturated colours in targets and stars using the L channel ... I would never have figured that out without looking at exemplar LRGB workflows. Using a new (to me) LRGB workflow, this is a completely reworked version compared to that I recently posted in the Beginners Forum. Still have some issues with flats that I'm working through. At some stage, I'll get more B and some Ha too. Details are:

EdgeHD 8" with 0.7 R, ASI294MM, Antlia LRGB
Shot across 2 nights - 11hrs 12mins total
L: 107 x 180s
R: 48 x 180s
G: 49 x 180s
B: 20 x 180s
Stacked and edited in PI, finished in PS. Cropped.

Higher-res version here (https://pbase.com/doogs38/image/173767069/original).
Any feedback gratefully received. Alex

[marc4darkskies]

An excellent image Alex! :thumbsup::thumbsup: Great detail & colour! Nicely done!

My only suggestion is to darken the sky - it looks milky (ie trim the black end of the histogram) and maybe do a pass with NoiseX.

Cheers, Marcus

[strongmanmike]

Hi Alex, although a tad on the faint side, this is a wonderful large galaxy and gets hit pretty regularly by southern imagers as the season brings it into good position and as your image shows, for good reason :thumbsup:

Since you asked for feedback :)...overall, it is a good job, the colour looks good and when viewed at small size, it "looks" quite detailed...however, inspecting the large version it is pretty clear that whatever deconvolution or sharpening you have used has distorted the details a little and I note some stars have been heavily muted or are missing altogether. I suspect some AI sharpening has caused this or slightly heavy handed deconvolution or similar? Some of the stars look a tad green too, this should be easy to fix.

Otherwise, a good effort though and an improvement over your original :thumbsup:.

Mike

[Doogs38]

Hi Marcus and Mike. Thanks for your feedback; it's much appreciated.

Marcus - once I read your comment about the image being slightly milky and noisey it was then immediately obvious in the image! I've tweaked the image accordingly.

Mike - you've highlighted something that I'm aware of but have struggled to understand how to improve using PI's beginner-friendly, simpler tools. In essence I use a fairly generic workflow: basic LRGB combo, background extraction, simple colour correction, GHS, RC Astro's tools and basic histogram and curves tools (with some final minor tweaks in PS). I don't do any sharpening in PI beyond using BlurX. Perhaps it would help to use the unsharp mask tool too? I could be wrong but I suspect the real magic to preserve/enhance detail at a micro level lies in PI's advanced tools like multi scale processing and deconvolution. I've yet to learn these tools but reckon now is as good a time as any :D And the stars hmmmm that was me trying to be clever by thinning out the dense star field, but I went too far. I'll fix that!

[Doogs38]

FWIW, here's a tweaked version that corrects the background, noise and my hosing of the stars, and includes an inaugural attempt to use PI's multiscale linear transform tool. Can't say I'm happy with the MLT's output ... I have much to learn. Alex

[Dave882]

Mate that’s a cracker! I really think you’ve done an excellent job and the detail and colour is great. Regarding the sharpening, I can see what Mike’s taking about, but I reckon it’s only just a tad overdone, really only noticeable when you zoom in on the hi res version. I’ve found that running multiple soft applications of BlurEx (instead of a single heavier application) can be useful, but tbh I’ve really struggled with it on broadband galaxy shots and am yet to find a result with it I’m truely happy with.

EDIT- I just saw the repro and I think the MLT has caused it to loose a bit of its natural feel but hard to tell from a 200kb pic lol. But honestly…I’m really enjoying your images and I’m sure you’ll find the right combo of processing that suits your data well so keep at it!!!

[Doogs38]

Hi Dave and thanks for the feedback. That’s good advice about BX and I’ll give your suggestion a go. I just tried PI’s MLT and really liked what it did to some of the fainter areas of the galaxy’s arms - it drew out some nice detail - but it nuked the core and turned it into a mess but that might be correctable using masks :shrug: I’ll keep trying! Alex

EDIT: Ahhhh you saw what MLT did to the core - what a mess, eh. I’m going fix that tomorrow!

[Dave882]

A range mask would help isolate the core area I reckon. Dead easy to set up