Teasing out faint details

[stevewanstall]

I have collected LRGB subs for M57 and was able to  produce a reasonable image. 

Having read out the outer layers, I decided to collect a lot more red subs in order to see this faint detail. I have collected around 5 hours worth and when  the data  is (over) stretched, I can see the outer layer.

 

My problem is, is there any way to combine this with the original image without it looking like a car crash? I have attempted to  use a select tool and eraser but  it looked horrendous.

Should I just :

1. Get a lot more red  data

2. Match this with B and G so that the image is colour balanced (ish) from the start?

 

Thanking you in advance for any suggestions.

 

[geordie85]

You can always try using layer masks 

[ollypenrice]

You'll need to reprocess from scratch because the original is significantly black clipped:

 

The shiny, jet black sky was an instant give-away but the histogram in Photoshop levels confirms it. There needs to be at least a little flat black line showing before the histogram pedestal starts to rise. Your faintest signal - that which you rightly want to bring into view - has already been discarded. A healthy histogram looks like this:

The peak of the pedestal rises a little to the right so no faint signal has been discarded. You need to watch this like a hawk throughout the processing job and only bring the black point in as the very last operation. (Also not you have two histo peaks which means one of your colour channels is out of alignment.

For the kind of localized faint shell you're trying to reveal I would begin by doing a normal 'stretch and process' job and save that. The outer shell may be hardly visible but don't worry about that till you have a nice basic image.

I would then make a copy layer and make the bottom active and the top invisible. In Curves I would then put a fixing point at the level of the background sky and another below that, then lift the curve just above the background. This should pull out the outer halo. Restore the curve to a straight line just above this so you're only stretching the faint part  you're looking for. There are fancy ways of combining both layers but I like easy, so I'd just use a small softly feathered eraser to take off the top layer where it's blocking the faint stuff underneath. That's how I did the outer halo of the Owl.

Olly

 

 

[Annehouw]

What Olly says, plus you might try the Screen, Mask, Invert procedure. 

See here http://www.astronomersdoitinthedark.com/dslr_llrgb_tutorial.php

If you go to the video clip listing, it is the 9th item. The rest of the tutorial is very good as well.

[stevewanstall]

6 hours ago, ollypenrice said:

You'll need to reprocess from scratch because the original is significantly black clipped:

 

The shiny, jet black sky was an instant give-away but the histogram in Photoshop levels confirms it. There needs to be at least a little flat black line showing before the histogram pedestal starts to rise. Your faintest signal - that which you rightly want to bring into view - has already been discarded. A healthy histogram looks like this:

The peak of the pedestal rises a little to the right so no faint signal has been discarded. You need to watch this like a hawk throughout the processing job and only bring the black point in as the very last operation. (Also not you have two histo peaks which means one of your colour channels is out of alignment.

For the kind of localized faint shell you're trying to reveal I would begin by doing a normal 'stretch and process' job and save that. The outer shell may be hardly visible but don't worry about that till you have a nice basic image.

I would then make a copy layer and make the bottom active and the top invisible. In Curves I would then put a fixing point at the level of the background sky and another below that, then lift the curve just above the background. This should pull out the outer halo. Restore the curve to a straight line just above this so you're only stretching the faint part  you're looking for. There are fancy ways of combining both layers but I like easy, so I'd just use a small softly feathered eraser to take off the top layer where it's blocking the faint stuff underneath. That's how I did the outer halo of the Owl.

Olly

 

 

 

Thank you for the detailed advice. I shall try and put this into practice over the next couple of days.

6 hours ago, Annehouw said:

What Olly says, plus you might try the Screen, Mask, Invert procedure. 

See here http://www.astronomersdoitinthedark.com/dslr_llrgb_tutorial.php

If you go to the video clip listing, it is the 9th item. The rest of the tutorial is very good as well.

Thank you for the link, again, I shall try this out.

Onwards and upwards!