NGC1333 - peeling back the layers

[Filroden]

Having been inspired by some of the phenomenal images of NGC1333 I've seen on here recently, I wondered what I could get with my set up. Until now I've restricted myself to imaging brighter and larger targets as the alt-az mount limits my exposure time. Having recently also acquired the ZWO ASI1600MM-C, I thought it was worth a go given its much better sensitivity and lower noise than my DSLR.

I collected lights over four nights in late October and November between the endless clouds, and full sets of flats the following morning after each session. I had already captured master bias and darks. The following image shows the number of subs I used to create each version.

Versions 1 and 2 used the same data but were processed slightly differently. By version 4, I had gathered many more subs but, using both the Blink tool and the sub-frame selector script in PixInsight, I was more ruthless in selecting which subs to take through to processing so version 4 has a shorter total integration on L but longer on RGB.

As you can see, both quantity of subs and quality have had an impact. I'm still many many hours from having enough data but I was pleased to start seeing features slowly reveal themselves as I gathered more data. This for me really shows there's never not a reason to go back to a target and get more data!

Version 1

Version 2 - a flatter gradient and a slightly tighter crop

Version 3 - starting to see hints of the dark stuff

Version 4 - starting to show some of the dust?

I appreciate this still needs a lot more work, both in terms of data to be captured and in the quality of the processing. However, having at first thought I'd not capture anything, to seeing the central nebulosity, then seeing those hints of dark clouds that actually matched the shapes in much better images and finally seeing the start of dust being visible, is really motivating.

Version 5 - I had a really clear night and took the opportunity to add a lot more subs to this project. All told, I think this now stands at 163 min of L, 44 min of R, 54 min of B and 52 min of G. All subs of either 30s or 45s at -20C, 300 gain and either 0 or 50 offset. All calibrated with bias, darks and flats and processed in PixInsight with some finishing touches in Lightroom.

Version 6 - this is now up to about 3hrs of L and 1hr each of RGB

Version 6.1 - As v6 but without the colour cast

Version 6.5 -  This is the same data as v6 but I've pushed the background much harder (probably too hard) and balanced the colour a little better. I've also rotated the image to match the first 5 versions.

 

[graemlourens]

Great writeup Ken.

Amazing what you pulled out with an Alt/Az and those low exposure times.

Kind regards, Graem

[happy-kat]

Will be interesting to see this to continue to unfold as you collect more data

[Filroden]

Aye. And it's nice that I'll be able to see it develop with each session adding more data and reducing the noise. This is what I'd call my first real project. 

[Filroden]

In the hopes that the forecast is correct for this evening, I'm collecting darks at new settings - 400 gain and 10 offset at a temp of -30C. With luck I'll get a clear run through from 18:00 to 21:00 when NGC1333 rises above my mount's alt limit.

[Filroden]

Well, after running a range of test exposures a gain of 400 is way too high for LRGB. It's probably fine for narrowband but even at 15s it was starting to look very overexposed. Dropping back to 300 gain and no offset.

[Filroden]

I had a really clear night and took the opportunity to add a lot more subs to this project. All told, I think this now stands at 163 min of L, 44 min of R, 54 min of B and 52 min of G.

All subs of either 30s or 45s at -20C, 300 gain and either 0 or 50 offset. All calibrated with bias, darks and flats and processed in PixInsight with some finishing touches in Lightroom.

Version 5 has been added to the first post. I don't think I've done a good enough job with the processing this time. I've not done as good a job on the noise (though the base noise was much lower than the previous versions) and I think the colour could be better.

[happy-kat]

There is more in version 5 showing the dark stuff. The colour is a lot browner, but looking at google images and a POD Nasa image I can see that there is brown in it, keep going I say it's building very interestingly.

[wimvb]

Great image. Amazing what can be achieved by this camera and an Alt/Az setup. The data should be filling up your hard drive pretty fast.

[Filroden]

26 minutes ago, wimvb said:

Great image. Amazing what can be achieved by this camera and an Alt/Az setup. The data should be filling up your hard drive pretty fast.

Thank you, it is. I think Friday night's effort alone added about 13Gb to the stack!

[Filroden]

Added version 6 to the first post

[wimvb]

Great. Version 5 rather than 6 for me. 6 looks a bit magenta. 5 may look green, but that may well be because of 6. 5 looks better in the full view

[Filroden]

42 minutes ago, wimvb said:

Great. Version 5 rather than 6 for me. 6 looks a bit magenta. 5 may look green, but that may well be because of 6. 5 looks better in the full view

I hadn't noticed until you mentioned it. I'll reprocess it to keep the magenta down. I think I know what has done it. I often find I don't need SNCR to remove green but if I'm not careful it adds a red cast and I don't spot it. I think I've applied it this time and either need to dial back the amount or not apply it at all.

[Filroden]

I've added a new v6.5.  This is the same data as v6 but I've pushed the background much harder (probably too hard) and balanced the colour a little better. I've also rotated the image to match the first five versions. 

[wimvb]

I like your evolution of this image. I think you are at the limit of what your data will allow. In the latest version you have great contrast, but you can probably increase the black point slightly.

Thanks for sharing

[Filroden]

4 minutes ago, wimvb said:

I like your evolution of this image. I think you are at the limit of what your data will allow. In the latest version you have great contrast, but you can probably increase the black point slightly.

Thanks for sharing

I agree. I need darker skies/better seeing I think, or many many more hours of data. Neither of which I'm likely to see this year! However, I'm pleased with the progress and I've learnt a useful technique in improving background contrast so it's all good stuff

[Mr Spock]

Looks a great project. V6 would look great without the colour caste but not pushed as in V6.5.

[Filroden]

15 minutes ago, Mr Spock said:

Looks a great project. V6 would look great without the colour caste but not pushed as in V6.5.

Here's version 6 without the cast. I see what you mean.