ν scorpii disappointment

[alacant]

Hi everyone

No laughing please. There's supposed to be blue-white nebulosity here, but despite over 2 hours, almost nothing.

Any processing tips for this stuff?

Cheers and TIA for your time.

700d @ ISO800

[ollypenrice]

The simplest way is to use Curves. This is in Ps but many graphics packages have it. First put a fixing point on the curve at at the level of the darkest parts of background sky. That's the second highest point on the curve below. Put a fixing point beneath it. Next, raise the curve just above the background (the third highest point on the curve) and, finally, restore the curve at the top as far as possible without putting a negative bend into it. You're just trying to hold down the stars. This was a qickie but with careful attention to the shape of the curve you can concentrate the change only onto the faint nebulosity. You could also try a similar but slighter adjustment to the blue channel only but you're no longer being so honest with the data.

The pinning of the lower part of the curve has the same effect as masking out the background sky. There are plenty of masking techniques as well but the kinky curve trick is the easiest in my view.

Essentially 2 hours is not long if you're going for faint signal.  

Olly

[alacant]

Thanks. Works well.

I came up with this. Probably too much now. 

I think this with another hour or so tonight will help.

[MarkAR]

Does look like a faint area, could be you need a few more hours to help tease it out.

[alacant]

2 hours ago, MarkAR said:

a few more hours

I agree. I think with really faint reflection stuff like this, the only way is to sit it out night after night.

With all the other nice stuff around at this time of year, I just can't convince myself to do it!

 

[ollypenrice]

4 hours ago, alacant said:

Thanks. Works well.

I came up with this. Probably too much now. 

I think this with another hour or so tonight will help.

Looks good to me. Nice streamers appearing in the dust.

If you want to get clever you could start with the original and make a copy. De-star the copy and then give it the kinked curve treatment, only harder. It'll probably then need a de-noise. Finally apply this as a top layer over the original in blend mode lighten. If you do this, the  top layer's dark background sky will not appear in the blend, and the stars will be entirely unaffected. The de-noise will only be present in the highly stretched nebulosity where it's needed.

Olly

Edited May 31, 2020 by ollypenrice