NGC 6992 - Eastern Veil Nebula

[OzDave]

Here is my initial processing attempt at the Eastern Veil Nebula using Pixinsight. It's really an experiment to see what I could process while learning how to use PI. I plan to do a reprocess using other techniques once time permits.

The data consists of 10x20mins Ha, 9x20mins OIII, 9x20mins SII, no binning. I've combined it with the Hubble palette as should be apparent.

This is also my first go at a narrowband image, so any feedback as to what to do better / different would be great.

Regards,

David

[OzDave]

I did this image as a straight SHO combination, with no tone mapping or luminance layers or anything. I reckon I'll have another go at processing in Photoshop to see what I can do there compared to Pixinsight. However, I'm wondering what other colour mapping palettes people use? I have never been a big fan of the Hubble palette and I read on here that others feel the same. So what are the alternatives? Are they simply just different combinations of S/H/O into R/G/B? Or do people also mix the narrowbands to form each channel as a combination of multiple narrowband images?

David

[Gina]

The amount of SII emission in this is very low and hence this object doesn't work very well with the Hubble pallette IMO. I've mapped this as Ha to red, OIII to green and OIII + 25% Ha to blue - with the Ha added as a "lighten" layer in Ps. That gives the Ha a pinkish colour (stands out more than the plain red and represents the contribution that Hb would give) and the OIII as turquoise (green/blue).

[OzDave]

Hmmm, not a lot of SII emission. Respectfully, I beg to differ . My SII subs and the master show quite a lot of signal. Quite comparable to the OIII and Ha. Though that does pose an interesting question...where is the red in my image since Hubble palette has R=SII???

I suppose it could be that I'm just seeing the SII screen stretched a lot more and so it looks similar to the other channels, but when mixed with the other channels, the relative strength of the SII is less and so it doesn't show through much. I'll have to figure this one out when I reprocess it in photoshop.

[swag72]

Have you tried blending just the Ha and OIII as initially an HOO palette and then from there creating a synthetic green channel? I use Noel's actions to do this in Photoshop. Can't offer any help on how to do it manually though, sorry. This blend seems to give quite a nice natural rendition - May be worth a try.

[OzDave]

I've done a total reprocess, this time following an LRGB approach using Ha as the Luminance and a blend of HA, OIII, SII for the RGB. I paid more attention to noise reduction also. I processed the whole thing in Pixinsight again. I had a go at it in Photoshop, but it seems that Photoshop only works with integer-valued pixels and this seemed to introduce various artefacts as I stretched etc. Also, Pixinsight has some various sophisticated noise reduction tools and that really made a difference. Here is the result. I think it is much better than the first go, but I still have a lot to learn.

[Gina]

WOW! That's a lovely image - very colourful

[swag72]

The detail on this is superb, but I find the background just a little 'lumpy' for my liking probably due to the noise reduction. The colours are a little different to the norm. Well done!

[OzDave]

Yeah the background starfield hasn't come out as well as I'd have hoped. It's not terrible, but is a bit lumpy as you say. I've not really had to process such a dense starfield before either. Added to that, my subs had a slight drift and the corners weren't really "flat". This is down to guiding and optics. The lumpyness comes from noise reduction probably as you suggest.

I may have another go at this sometime and see if I can get the starfield to look better. But I may wait till I can get some better data.

David

Sent from my iPhone using Tapatalk

[swag72]

You could always add a little noise back in. That sounds counter productive, but it really does mask an awful lot in a tricky background I found.