Antares region widefield

[andrewluck]

Alongside my image of NGC6188 the other main project during my visit to Tivoli was the Antares, M4, Rho Ophiuci region. This required a three panel mosaic with the FSQ-106 and Moravian G3-16200. I exposed 1 hour each of RGB for each panel for a total of 9 hours. Having assembled the mosaic, this is where processing currently stands (resized to 20% as the original is 42 Mpixels).

Andrew

[Allinthehead]

That's a stunner. Lovely chocolatey dusty detail.

[MilwaukeeLion]

Like NGC 6144 peeking through, M4 detail, entirety is gorgeous.

ML

[simmo39]

thats a real wow image!

[GuLinux]

Sexy 

[StuartJPP]

Very nice!

[happy-kat]

That's really absorbing. Great feeling of 'vortex'.

[RichLD]

Beautiful!

[Barry-Wilson]

Very envious of this image - a target on my list when I can view that far south.  Terrific Andrew, quite beautiful.

[andrewluck]

Comments are very much appreciated, thanks.

Processing is entirely in Pixinsight but I have some remaining problems. Colour calibration is a nightmare for this image. Firstly, there's very little background sky and second, the stars are predominantly red due to being dimmed by the dust, which means that the usual tools don't work very well. After a lot of trial and error, I just carried the settings from an unlinked auto-stretch into HistogramTransformation and this gave the best colour rendition for the various components of the nebula. Having got to the end of processing though, the sky at lower left is very blue. I'm in two minds about this; I don't think it adversely affects the overall composition too much but it's still bugging me that it isn't right. I think I'm going to have to return to the beginning and have another go. BackgroundNeutralisation using a preview from the lower left corner and then play with the mid range sliders until it looks right.

The other issue is a slightly dark halo around the smaller globular but the addition of a circular region to the mask used for LocalHistogramEqualisation will probably fix this.

Tivoli is now  fully booked for next year so it's going to be two years before I'm back there again.

Andrew

[andrewluck]

Some more work and I've isolated and subtracted a blue / red gradient that had slipped in across all three panels. I could then neutralise the background against a small area bottom left and colour calibrate with the stars on the left hand side of the image.

Andrew

[ollypenrice]

Brilliant work on the re-do. This is surely one of the best widefield targets in the sky, if not the best, and you've done it proud.

Alas, although we can get to it from the south of France, we are shooting through too much atmosphere and this makes the gradient problem so difficult to deal with. As you say, what is there to define as background?

Great stuff.

Olly

[andrewluck]

Thanks Olly; it is a stunning piece of sky to work with.

Antares crossing the meridian at 86 degrees altitude definitely helps . From the UK, I've taken a picture of M4 when it was barely 5 degrees off the horizon and that's the highest it gets; the air mass is about 6 down there. The other thing that really makes a huge difference is the total lack of light pollution at Tivoli. Shot noise from the sky background is limited to airglow and there's very little noise reduction required on the image.

Andrew