NGC6888 Crescent Nebula

[Jonk]

Firstly, this is not my data, it's my friend's (Martin, @Urban Dome) taken from his home in Eastleigh.

It was taken using a SW Esprit 120 and a Starlight Xpress mono CCD (I'm not sure which one), on an Intes Micro Alter D6 mount during June and July under less than the darkest skies in Eastleigh, Hampshire. It has a pixel scale of 1.11 arcsecs/pixel.

Exposure time was 18 x 1200s for each Ha, OIII and SII Astrodon 3nm filters (need to check this).

Martin's Pixinsight processing (he's fairly new to it) effort is here (mapped HOO):

He sent me this image, then the calibrated stacks followed so I could have a play, with my effort here:

I mapped it SHO, but as there's so little SII, I may revisit as a bicolour HOO.

This is also a testament to his observatory now being fully automatic, that he regularly controls from bed via an ipad (so I'm told!).

Hope you like it.

Edited September 1, 2020 by Jonk
Typo

[MarkAR]

Superb data, first one is definitely over saturated but shows some really good colour possibilities.

Your version looks great, maybe bring up the red a little, does look very brain matter grey but the detail is superb.

[Jonk]

I've tweaked the jpg a bit (maybe too much, I'm not at home near the original data at the moment), and raising the red does improve the overall look, but too much purple is being introduced in the background.

The noise is also increased, which is something I need to learn to control better.

[Jonk]

I've had another play with the data, this time mapping HOO bi colour and trying to spend more time on the individual channel detail prior to combining.

It's pretty good, I'm pleased with it - it's so tempting to push each stage, and I find I'm forever going back and forth to decide which looks better!

I might try SHO again, with more red, as per the jpg test above.

 

 

[MarkAR]

That is excellent, I would walk away from it now.

[tomato]

I think your final version is the best, that’s a fine Crescent Nebula. I always feel after posting my images on SGL that they could be improved, and  invariably I’m proved right. 
That’s the trouble with the processing side of AP, it is always open ended. At least with the data capture you get a definite set of subs from each session, which cannot be improved until the next one, with processing it is how long can you keep staring at a monitor.

[Jonk]

Thanks all, as nice as it looks there’s still lots to learn!

[Stub Mandrel]

I think you have pulled out much more of the fainter nebulosity.

Why not mix in about 10-20% of the original version as colour only, just enough to lift yours without saturating it?

[Jonk]

On 02/09/2020 at 19:00, Stub Mandrel said:

I think you have pulled out much more of the fainter nebulosity.

Why not mix in about 10-20% of the original version as colour only, just enough to lift yours without saturating it?

One thing I don’t know enough about is layers in Photoshop. Once Pixinsight has done it’s thing up to channel combination and background adjustment or colour calibration in the case of rgb, I usually go into Lightroom as I’m more comfortable using that.

I will have a go at what you suggest though, the main thing is colour noise... I need to learn about that one!

[Stub Mandrel]

19 hours ago, Jonk said:

One thing I don’t know enough about is layers in Photoshop.

Very easy, if the two images have the same crop, just paste one over the other. It will create a new layer and all you have to do is change its mode to 'colour' (or luminance if the more detailed image is 'on top') then adjust its transparency percentage to taste.

If the same scale but different crops, you will need to manually line the top one up - set its transparency to 50% to facilitate this.