Ngc5128

[peter_4059 (Peter)]

Another one from the 2016 Astrofest archives finally processed. A bit more data in this one (4 hrs 20 mins total integration) so quite a lot easier to process. Once again I followed the book although I used the batch preprocessing this time which saved a lot of time. Based on the experience and advice from the NGC6744 image I stuck with HT stretches for both the Lum and RGB.

As always tips/tricks and comments welcome.

Thanks for looking!

[cometcatcher (Kevin)]

It's quite a beauty Peter.

[Ryderscope (Rodney)]

Looking very nice Peter. Nice smooth processing of the galaxy halo. My leaning here would be for a little less brightness and deeper colour in the core but that is probably just me. A great rendition of this popular object. Seems to be a narrow field of view, what are the hardware details for image capture?

[RickS (Rick)]

Looks good, Peter! A little more saturation in the blue areas would add a little icing to the cake.

Cheers,
Rick.

[peter_4059 (Peter)]

Thanks for the feedback. I struggled a bit to get saturation in the blue areas - perhaps because the luminosity was too high in those areas?

[RickS (Rick)]

Originally Posted by peter_4059

Thanks for the feedback. I struggled a bit to get saturation in the blue areas - perhaps because the luminosity was too high in those areas?

That could be the reason, Peter. I always find that orange stars oversaturate easily while blue ones need help to show even a little colour.

Using ColorSaturation with a curve that favours the blues is one useful option. ColorMask can also help provided there's a little blue there already. Sometimes I have resorted to PixelMath to make a mask of areas where the blue channel is stronger than the average of the red and green channels. Blurring star chrominance can also help bring some colour into blown out star cores.

Cheers,
Rick.

[Retrograde (Pete)]

That looks great Peter!

[peter_4059 (Peter)]

Originally Posted by RickS

That could be the reason, Peter. I always find that orange stars oversaturate easily while blue ones need help to show even a little colour.

Using ColorSaturation with a curve that favours the blues is one useful option. ColorMask can also help provided there's a little blue there already. Sometimes I have resorted to PixelMath to make a mask of areas where the blue channel is stronger than the average of the red and green channels. Blurring star chrominance can also help bring some colour into blown out star cores.

Cheers,
Rick.

Thanks for the feedback Pete.

Rick,

I took a look at the linear RGB without STF and the blue stars are visible. When I apply STF the RGB levels in the centre of the largest blue star go to 0.45/0.43/0.86 so not saturated. It seems one of the steps I'm performing post HT is boosting the Red and Green as the same star in the final image is 0.998/0.998/0.999....maybe the colour balancing?

[RickS (Rick)]

Originally Posted by peter_4059

I took a look at the linear RGB without STF and the blue stars are visible. When I apply STF the RGB levels in the centre of the largest blue star go to 0.45/0.43/0.86 so not saturated. It seems one of the steps I'm performing post HT is boosting the Red and Green as the same star in the final image is 0.998/0.998/0.999....maybe the colour balancing?

Hi Peter,

It would be interesting to step back with History Explorer and determine where the blue is being attenuated. It could be the colour calibration but it's not too difficult to check and be sure.

Cheers,
Rick.