Iris Nebula, first attempt

[david_taurus83]

Hi everyone. I made use of the good weather we had last weekend to get back into imaging, first proper outing since February! I choose NGC7023 as it's a nice easy target for beginners lol!

 

Taken from my street light cursed back garden over 2 nights:

 

64 x 180s at ISO800, Canon 600D on 200p F5

Dithered plus 10 darks each night

30 bias and flats for each night

 

Pre and post processed in Pixinsight. I think this one would benefit from a darker site and more integration. It may seem a bit black clipped but if I lift it more it starts to introduce blue/black mottling and light pollution. Even heavily stretched after stacking there isn't much detail in the outer dust field, but it's definitely starting to appear but just falls short due to the low exposures. Overall, I'm happy with my limited processing experience. I will definitely visit this again in the future. It's been a positive project overall. The AZ-EQ6 performed flawlessly, guiding was good, platesolving was effortless and I've sorted out my flats. Need to use A/V mode and an exposure value of +2. This shows the histogram on APT all the way over to the right. But if I open a flat in the free Iris software, it gives a peak ADU value of just under 7k whereas a fully saturated flat (15 seconds of flat panel at max brightness)  gives a peak value of 15.3k. I can also now confirm that my coma corrector needs the spacing sorted as the stars in the top right corner still have coma. I was unsure initially if guiding was an issue but i dont think it is. I have also found a nice quiet darker location to image from. Not a dark site but maybe bortle 5 and more importantly away from streetlights! Clear skies everyone!

[wimvb]

3 minutes ago, david_taurus83 said:

but if I lift it more it starts to introduce blue/black mottling and light pollution.

Nice image!

You can decrease the mottle by using noise reduction on chrominance only. Just create a luminance clone for a mask, apply inverted. Then use acdnr on the stretched image, or mlt on the linear image. Use chrominance as the target.

Masked stretch or Mark Shelley's arcsinh stretch are good for lifting weaker structures and retaining colour, when processing this nebula.

Good luck and have fun.

[david_taurus83]

38 minutes ago, wimvb said:

Nice image!

You can decrease the mottle by using noise reduction on chrominance only. Just create a luminance clone for a mask, apply inverted. Then use acdnr on the stretched image, or mlt on the linear image. Use chrominance as the target.

Masked stretch or Mark Shelley's arcsinh stretch are good for lifting weaker structures and retaining colour, when processing this nebula.

Good luck and have fun.

Thanks! I use a fairly linear workflow on Pixinsight. I've only watched 1 or 2 quick tutorials on YouTube. Need to watch some more in depth stuff and experiment. So to try your tip, extract luminance, use as an inverted mask and then perform noise reduction? I will give it a try, thanks!

[wimvb]

Just don't forget to stretch the extracted luminance before using it. (Been there, done that, got a black t-shirt as a souvenir  Saving unstretched images as jpeg is another favourite of mine.)

[david_taurus83]

17 minutes ago, wimvb said:

Just don't forget to stretch the extracted luminance before using it. (Been there, done that, got a black t-shirt as a souvenir  Saving unstretched images as jpeg is another favourite of mine.)

Stretch it, apply histogram transformation and then apply as mask?