Processing

As usual for these types of nebulae, I used an Optolong L-Ultimate for Hα/OIII data, and an Askar D2 for SII/OIII. I normally use an Optolong L-Quad Enhance for RGB data — in this case just the stars — but I actually forgot to use it this time! It doesn’t really make much difference for the stars though, as they’re bright and use just an hour of integration time.

As for the L-Ultimate, that’s 12 hours of data. I knew the SII/OIII component would be fainter, so I doubled that and collected 24 hours. Unfortunately, the SII/OIII was even weaker than I expected. This caused some issues during processing (outlined below) so I needed to take a slightly different approach.

If I were to tackle this target again, I’d be tempted to forego the SII/OIII aspect, and just aim to get a very high signal-to-noise ratio with the Hα channel. As it stands, it’s a really tricky target with an OSC set-up from a city centre. It may be a more realistic approach with full Mono, and definitely with darker skies!

I don’t have time for a full processing walkthrough this time, but the first steps are the same as I followed for the Wizard Nebula. The main difference came after running DBXtract to make an SHO image from the Hα/OIII and SII/OIII data. The SII/OIII channel was so weak / noisy in comparison to the Ha/OIII, I just couldn’t get a high quality result. So, I decided to try something new. I used NarrowbandHueCombination to mix together the Hα, SII, and OIII channels produced by DBXtract.

Check the image below to see the settings I used. I used red at Contribution 100 for the Hα channel; but Contribution 0.5 for both OIII (blue) and SII (green). This made the stronger Hα channel much more dominant. The end result isn’t as colourful as I’d initially planned, but the actual image quality was higher, in that it wasn’t ridiculously noisy.

After that, I used SelectiveColorCorrection to make the red, orange, and yellow colours a bit more distinct. Then it was a case of my usual processes, including UnsharpMark, NosieXTerminator, and DarkStructureEnhance.

Here are two images I initially made using my regular method. The don’t look so bad when viewed small, but when viewed original size on my screen I just wasn’t happy with the image quality.