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Old 05-02-2012, 10:15 AM
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g__day (Matthew)
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Photoshop Processing Question - Removing Red heat marks

Guys,

A simple question on preferred processing treatment. Attached is a single 900 second shot of NGC 2070 on a Canon 400D which has had the IR filter replaced (unit Eric did a while ago).

I've done a little bit of levels and curves and saturation with this - but I wonder what is the best way to get rid of the little red (heat?) flecks - that are brighter than the underlying nebulae I am trying to boost?

Is there a an effective way to grab these flecks somehow and either mask them out or blur them out? I've tried to do a colour select and either level or Gassian blur them out - but it didn't work - guess I didn't grab them successfully.

Many thanks,

Matthew

PS

Normally I stack everything through DSS with matching Dark, flat whites/darks, and BIAS shots. But for this example this frame has none of that treatment.
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Click for full-size image (NGC 2070 900 secs small.jpg)
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Old 05-02-2012, 10:38 AM
vanwonky (Dave)
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I am not exactly sure what "flecks" you mean in that image but have you tried using the 'Clone Stamp' or the 'Spot Healing' tools?
Cheers
Dave
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Old 05-02-2012, 10:59 AM
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mill (Martin)
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Matthew, the best way to get rid of them is just taking a dark as you have done before.
I used to try to get rid of the hot pixels with the magic wand in Photoshop but if you got many of them it is a pain in the you know where.
So it is easier to get some darks and be done with it.

Martin.
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Old 05-02-2012, 11:35 AM
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g__day (Matthew)
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Mills - no way would I try and magic wand out that many red flecks - it would take hours per frame! I think I am processing things in a very crude way...


I did not expect a simple fix, so let me ask another question.

Should I allow Deep Sky Stacker to combine shots of different durations or should I do runs of equal duration lights in DSS and stack them in Photoshop via layers and clever combines?

The other option to consider is should I graduate beyond DSS and start learning and using CCDStack?

* * *

Lets say I image NGC 2070 and have a set of light frames, four each of 600, 900 and 1,200 seconds duration. I have BIAS, flat whites (1/100 sec) flat darks (1/100 sec) and master darks (tifs created from 20 dark frames matching each light frame).

Does it help me in any way to do one run of DSS with 12 light frames and the three matching darks - or am I better off for some reason to execute three seperate DSS runs using light frames of only one duration to produce three corrected masters 600 secs, 900 secs and 1,200 secs and then combine these 3 corrected master shots in Photoshop?

* * *

I also out of interest tried combining just four shots - to 10 minutes shots and two 15 minute shots - so 50 minutes in total, with all flats, darks and bias combined - the result is below. Which looks to my eye much better.

Maybe I was adding some shots with too much noise and likely I have to process the dim data in much more effective ways. Looks like this is my next big learning curve!
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Click for full-size image (NGC 2070 00 hr 50 mn small.jpg)
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Old 05-02-2012, 11:35 AM
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Rigel003 (Graeme)
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It's a hard one as there's so much noise in the image. Not surprising with a 900 sec sub on a DSLR. It seems to have a fairly strong magenta cast overall too.

You could try using an inverse mask to preserve detail in the main nebula and then use the Replace Colour tool to select the noisy pixels in the background, then lower the saturation for these. Might need to do this step a couple of times selecting different shade pixels. While still using the mask you could also use the Reduce Noise filter to operate on the background. Here's an attempt along those lines.
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Old 05-02-2012, 07:50 PM
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mill (Martin)
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I used to many to show filters etc.
But i got this out of it.
When having many different exposures of different lengths then it is better to process them separately and then stack them or blend them in Photoshop.
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Click for full-size image (NGC 2070 testl.jpg)
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Old 05-02-2012, 08:10 PM
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jjjnettie (Jeanette)
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Try running the image through "Dust and Scratches" at a level of 2. Then fade back to 75% or so.
If it's affected your nebulosity too much, you can use it as a layer, and work with it that way.
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