IC1848 and soul nebula. SHO Newtonian image plus RGB stars.

[timh]

A couple of clear nights so time to hand in the home work..

SW PDS200 F4.5 (0.9X reducer) and ASI294 MC and MM cameras at 4.63 uM pixel size (0.95 arc sec/ pixel) - an image comprising 155 x 33s RGB OSC frames, 149 x 3min O3 frames (Astronomik 6 nm, gain 151), 75 x 3 min HA frames (Optolong 7 nm, gain 151) and 130 x SII frames (Optolong 6.5 nm). Mount was a CEM 70, guiding with PHD2 via a 80, 400mm guidescope plus ASI 120MM camera.

Capture was with Sharpcap 4.0 -- filtering on FWHM and brightness in livestacking with autofocus every hour or so. Processing in PixInsight. Starless NB SHO and RGB images were prepared using StarExterminator 2.05, combined using Pixmath, stretched using EXP, LocalHistogram Equalisation and curves with RGB stars re-added at the end.

The soul nebula is about 7000 ly distant and some useful notes on this region that set it into a wider context are here
https://www.astrobin.com/pip7fh/


It is interesting (although of course expected) to see how the hot blue (OIII) is found at the nebula core around the main giant type O ionising stars in the IC1848 star cluster -- and that there is also a secondary centre of ionisation towards the lower right of the image (not sure which are the ionising stars there). The S2 signal provides 3D information since it marks the less dense foreground ionisation edges.

Full image is here https://www.astrobin.com/bpa8vm/


Tim

[Menno555]

Great capture Tim! The HOO version looks very good here!
Question on StarXTerminator: did you ever compare the results from that with StarNet v2? I found that StarNet v2 did give a somewhat cleaner result.

Menno

[turfpit]

Tim

Good images and useful description - thanks. I prefer the HOO image but that is just personal taste.

Dave

[timh]

Thanks Menno, Dave, it has been satisfying to now have the PDS200 tuned up and properly collimated/ adjusted across the entire F 4.5 field - and of course to finally get some OK nights for imaging. The PDS200 plus SW reducer/ flattener is really quite an (relatively) inexpensive set up but I can't fault it.

Couldn't make my mind up between the SHO and max(SH)OO images. I wasn't originally going to bother with S2 at all but I got my filters mixed up and ended up with 6.5h of S2 by accident (having intended to use the O3 filter). But it worked out OK and I think the S2 adds some subtle detail

On the starnet 2 question no. I had starnet 1 and it often left ghosts behind. I tried starExterminator 2.05 and was immediately delighted with it because it just worked so well --- in terms of both the star masks and perfectly clean starless images. Apart from that I just went with a couple of reviews which rated StarExterminator 2 slightly better than starnet 2 -- where the tough comparative test was the ability to remove stars right up to magnitude 3 or 4 cleanly (as I recall).



Tim

[Menno555]

I had the trail version of StarXTerminator and indeed there were so little differences between the 2. But StarNet v2 being free, was an easy choice.
It has the disadvantage though that it's a stand alone app but that is changing: in the next version of SiriL, it can be incorporated in the workflow during processing. Curious how well that works

Menno

[oopfan]

Hi Tim,

I think that HOS (aka CFHT) might be a good tri-color combo to try since you have a strong SII stack. Here is a great tool for visualizing all combinations of tri-color and bi-color palettes:

https://www.bintel.com.au/narrowband-pr ... /index.php

Simply upload three registered NB stacks as jpegs. You won't be able to mix in your RGB stack but you can add that later once you find a pleasing palette.

Brian

PS: H/T to Dave (turfpit) for remembering the Url.

[timh]

Hi Brian,

Thanks for the link. OK so indeed why not give something different a try? Herewith using starless images the normal SHO and then HSO and finally HOS palette.

Not sure ... I think that the HSO is quite interesting which perhaps best highlights the SII as yellowy green, HA a naturalistic red and the OIII/ HA overlap then comping out as purple.

The starless images are quite striking. As a way of viewing the nebula they perhaps seem a bit out of context without the ionising stars added back (i.e otherwise it is not clear why the blue bits should be blue etc).

Actually one quite creative way of doing it might be to add back only the relevant stars that are actually associated with and at the same distance as the nebula and to screen out the foreground stars ? There is perhaps almost enough info in the databases to partly start to do that ?

Tim

[oopfan]

Tim,

Wow! SII really stands out in HSO. That's my vote! My CCD dies in deep red, so SII has always been a challenge for me.

Brian

[turfpit]

HSO for me. Adding the stars back should be interesting.

Dave