Gum Nebula (56 panels)

[CaptainCook]

This is the last update for this year! :-)

A few more panels (now 56 in total and well over 30 hours) taken on the great clear sky event of 27 & 28 June, as it will now be remembered.

The image now extends a bit more at the bottom left (estimate about 3 frames off carina) and also halfway into the other bit at the top next to Gum 12b, officially designated as Sh2-312.

I just got an Astrobin trial and it looks like I can finally get a full resolution upload, which is the main reason for this post and the original can now be seen here (https://astrob.in/full/ujaso3/0/).

For completeness my other high res mosaic (albeit 50% reduced) of the LMC is also here (https://astrob.in/full/z35f6x/0/).

Cheers
Gary

[AdamJL]

Now that is something! Goodness me, there's some incredible detail in areas that you'd never think to look. The background galaxies, the dark filaments... this is beautiful. Can't wait to see the complete image. Awesome work, Gary!

[CaptainCook]

Many thanks Adam, that's very much appreciated!....its been a right royal pain in the backside to do and if it wasn't for the weather (I started about 2 months late) I would've finished it, but onto next year.

[Ant0nio]

Hi Gary,
An excellent result so far & at 56 panels I can certainly relate to the "labour of love" analogy. I have the same Samyang lens & I've recently dipped my toes in dark waters of mosaic imaging.
I started with a four panels of M8 & now I'm up to 28 panels, the more I add, the more I multiply the pain involved :). I'm using Photoshop CC for post processing & stitching.
Would you be prepared to share some details of your workflow & the software you're using?

Cheers & thanks in advance,
Tony

[CaptainCook]

Hi Tony,
Thanks for your comment. I have added some details below which I hope you find helpful but feel free to ask anything I may have missed.

1) Imaging: I was consistent with each panel. I settled on 2 mins at f/2.8 using this lens as a good compromise between SNR and vignetting. I set myself a minimum of 32 min integration-I have sometimes got panels with more data (e.g. Vela) but excluded it from the final mosaic so the noise is consistent which helps the compositing imo and definitely a more consistent result. The 32 min panel has proven just about achievable even with the bad weather- sometimes I was getting only one 2 min sub in a night! To also be consistent I never imaged below 40 degrees even though I could probably have gone down to 30 before obstructions etc.

2) Planning: I have used Telescopius which I can definitely recommend. This allows you to enter (or prospectively set) your sensor angle, grid size and overlap (which I set to 18%). You can get this angle from plate solving/astrometry etc and check at any point eg you know how the lens focus ring is very stiff and once or twice I moved the whole lens accidentally. Even at 18% the composition can struggle where there is no obvious structures to match in hindsight maybe use 20%.

3) Composition. I use Microsoft ICE (Image Composition Editor) it is absolutely fantastic and I dont know why this is no longer supported but you can find a download if you go looking. Incidentally, I have used this for terrestrial and MW panoramas too. I even used it to put my virtual backyard into Stellarium.

Sometimes the automated tool fails where you have panels that basically contain fresh air, which meant I to separately do that section with numbered panels before manually loading it into ICE to give it a helping hand. You will get what I mean if you start using it. Then I added that small panel to the rest of the images. In other other words my 56 panels might end up being 60 images input into ICE.

4) Processing. I did this in PI but kept it very simple. The steps I used were ABE, noise XT for each panel prior to ICE. Once the mosaic was completed I used Starnet (again in PI) and curves/layers in gimp to add back in. At that point you are talking 1.5 GB- Starnet takes 40 mins on my laptop. I then reduce 50% and save as jpg etc

I look forward to seeing your mosaics on here!

We need more black and white widefield stuff :rofl:

Cheers
Gary

[Ant0nio]

Hi again Gary,

Thank you for your detailed reply. It seems my approach is quite similar to yours as far as the planning & imaging although I'm shooting at F2 with a full frame OSC camera. The larger sensor means less panels are needed but the down side is more distortion in the corners.
Initially I was using ICE for the composition but it failed because the panels were too dark & needed more stretching I think. Originally I thought it would be best to do the majority of the post processing after the full image was composed but I realise that was a mistake now & you've helped to clarify that.
I'll give ICE another go now using Background Extraction in Siril & noise ext. in Photoshop as I don't have PI.
Thanks again for sharing your work flow Gary, it's been very helpful to compare notes. I'll post an interim mosaic shortly.

Cheers,
Tony