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  #1  
Old 13-09-2016, 06:05 PM
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Relacing narrow band stars with RGB stars.

Hi,
Could someone please tell me how to replace narrow band stars with RGB stars. I have tried this a few times but always end up with dark circles around the RGB stars.
Thanks.
Mark.
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  #2  
Old 13-09-2016, 06:18 PM
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What software are you using, Mark? I can give advice on how to do it in PixInsight but that may not be much help to you...
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Old 13-09-2016, 07:46 PM
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Hi Rick. I am using Photoshop CC.
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Old 13-09-2016, 09:01 PM
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Hi Rick. I am using Photoshop CC.
Sorry, Mark. Hopefully somebody who groks PS can help.
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  #5  
Old 13-09-2016, 10:02 PM
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No worries. Thanks Rick. I keep saying I should buy PixInsight.
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  #6  
Old 13-09-2016, 11:31 PM
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Try using Straton or Annies Astro Actions to remove the NB stars with one click.
Basically using JP Metsavanio's tone mapping method but faster. http://www.skypixels.at/downloads/ade/Tone_Mapping.pdf
Then layer up your pre-aligned RGB stars in lighten or screen blend mode.
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Old 14-09-2016, 06:11 PM
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Thank you Andy.
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  #8  
Old 14-09-2016, 10:41 PM
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Quote:
Originally Posted by Andy01 View Post
Try using Straton or Annies Astro Actions to remove the NB stars with one click.
Basically using JP Metsavanio's tone mapping method but faster. http://www.skypixels.at/downloads/ade/Tone_Mapping.pdf
Then layer up your pre-aligned RGB stars in lighten or screen blend mode.
Have to say I am appalled by this "tone mapping" technique.

The process distorts the real colours of objects and puts colour into places where it becomes meaningless.

Might as well get the airbrush tool and paint in some colours because they look nice....sorry...simply don't see the point.
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Old 15-09-2016, 06:29 AM
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What method would you use Peter? Can you point me in a direction?

Mark
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Old 15-09-2016, 09:16 AM
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Quote:
Originally Posted by Peter Ward View Post
Have to say I am appalled by this "tone mapping" technique.

The process distorts the real colours of objects and puts colour into places where it becomes meaningless.

Might as well get the airbrush tool and paint in some colours because they look nice....sorry...simply don't see the point.
What's your objection, Peter? You're perfectly entitled to be appalled. Just wondering why. Applying a stronger stretch and heavy noise reduction to the weaker components of a narrowband image is common practice. Otherwise the majority of Hubble palette images would be solid green.

Cheers,
Rick.
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  #11  
Old 15-09-2016, 10:01 AM
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What method would you use Peter? Can you point me in a direction?

Mark
Fair 'nuff. I'd also use Pixinsight....but if you must use Photoshop...Assuming you've registered the images, I'd suggest a layered mask of the RGB stars, feather the edge to suit (about 1.5-3.5 pixels) and place the layer on top of the NB stars. You might need to do this a couple of times at different feather levels to remove any dark rings.
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Old 15-09-2016, 10:12 AM
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Quote:
Originally Posted by RickS View Post
What's your objection, Peter? You're perfectly entitled to be appalled. Just wondering why. Applying a stronger stretch and heavy noise reduction to the weaker components of a narrowband image is common practice. Otherwise the majority of Hubble palette images would be solid green.

Cheers,
Rick.
I thought I was pretty clear on why...but no matter....to re-iterate, the extreme noise reduction and extreme stretch artificially blurs and extends all fine-structure (and real) details and replaces them with a fuzzy mess....in short you get colour in places where there is none and lose it in places where it should be prominent. The only real fix for lack of signal is more exposure.

Suffice to say, this is not the technique I used when I submitted this H-alpha blended image to "The malins"
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Old 15-09-2016, 10:46 AM
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I thought I was pretty clear on why...but no matter....to re-iterate, the extreme noise reduction and extreme stretch artificially blurs and extends all fine-structure (and real) details and replaces them with a fuzzy mess....in short you get colour in places where there is none and lose it in places where it should be prominent. The only real fix for lack of signal is more exposure.
OK, so it's just another technique that can produce appalling results when misused/overused. I can certainly understand and agree with that
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Old 15-09-2016, 03:59 PM
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OK, so it's just another technique that can produce appalling results when misused/overused. I can certainly understand and agree with that
Don't mind me Ric....just a peeve of mine.

There are so many sow-ear images out there that some try to turn into silk-purses by means of star shrink/CA removal/motion blur/noise removal/unsharp mask/decon/etc./etc. ...rather than stepping back and looking critically at their raw data.

Good data on the other hand simply doesn't need much post-processing to give an image that "Wow!" factor IMHO.
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Old 15-09-2016, 05:24 PM
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On the other hand, I think that experimenting with numerous processing tools and techniques, breaking boundaries and over-cooking astro images brings invaluable experience that is essential in personal growth as an amateur astro imager and it allows for acquiring in-depth understanding of how to skilfully process astro data. I reckon it would be quite a challenge to find an amateur astro imager who have never clipped a histogram or destroyed good data with noise reduction. Besides, everyone is at a different stage in their journey and have different circumstances, so acquiring good data may not always be possible.

Just my two cents.
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Old 15-09-2016, 06:48 PM
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On the other hand, I think that experimenting with numerous processing tools and techniques, breaking boundaries and over-cooking astro images brings invaluable experience that is essential in personal growth as an amateur astro imager and it allows for acquiring in-depth understanding of how to skilfully process astro data. I reckon it would be quite a challenge to find an amateur astro imager who have never clipped a histogram or destroyed good data with noise reduction. Besides, everyone is at a different stage in their journey and have different circumstances, so acquiring good data may not always be possible.

Just my two cents.
Nah.....I'm thinking you've put the cart before the horse.
You wouldn't try to palm off a photo-shoot of a bride on her wedding day by taking out of focus .jpg images, with motion blur and the wrong colour temp...then hope like hell there is a Photoshop filter to fix the mess. (You'd also probably get sued )

Also, you don't need a $100k rig to get good data. There are simply some basics you have to get right first up.

In focus? If not re-check and shoot again!
Stars round ? If not check polar alignment, tracking, auto-guiding parameters, mechanicals until they are.
Image noise? Insufficient exposure time/ bad calibration frames. Maybe both. More telescope time and nail your reduction data prior to image calibration.

Only then should you fuss with the smoke and mirrors of post-processing...
that's my 5 cents worth
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Old 15-09-2016, 07:02 PM
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I was mainly referring to this comment:
Quote:
Originally Posted by Peter Ward View Post
Have to say I am appalled by this "tone mapping" technique.

The process distorts the real colours of objects and puts colour into places where it becomes meaningless.

Might as well get the airbrush tool and paint in some colours because they look nice....sorry...simply don't see the point.
As for data quality, most of us here seems to struggle with getting the mechanicals spot on (mainly because of using a mass-production but affordable mount), thus data is often substandard and hence the search for processing tools that help to at least somehow hide imperfections in the data.

Just my 10 cents
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  #18  
Old 15-09-2016, 08:06 PM
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Quote:
Originally Posted by Slawomir View Post
I was mainly referring to this comment:

As for data quality, most of us here seems to struggle with getting the mechanicals spot on (mainly because of using a mass-production but affordable mount), thus data is often substandard and hence the search for processing tools that help to at least somehow hide imperfections in the data.

Just my 10 cents
I'll see your 10 cents are raise you twenty

I agree...but suspect many astro-imagers are simply using a focal length that is simply too terse for the rest of gear they are using.

Good deep sky data at 3 metres (or more) FL is hard to get!....even for top shelf gear (mainly due seeing)....but there are many sublime images in the 500mm to 1100mm that simply didn't need a gold standard in tracking ability....just a critical eye and attention to details.

Nail the focus, nail the tracking/guiding and go deep when you have mastered them....but not before, as GIGO applies (Garbage IN, Garbage Out)

Only then should you fuss over the software to best show-off your solid foundation work.
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Old 15-09-2016, 08:35 PM
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I'll see your 10 cents are raise you twenty

I agree...but suspect many astro-imagers are simply using a focal length that is simply too terse for the rest of gear they are using.
I totally agree. Not sure where this quite common amongst deep space imagers big scope on EQ6 trend originates from...I'm honestly struggling to consistently get quality data at 570mm and 1.33" per pixel with my AZ-EQ6...

Quote:
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....but there are many sublime images in the 500mm to 1100mm....
Thank you Peter!
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  #20  
Old 15-09-2016, 11:02 PM
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Quietly sitting back, munching popcorn and enjoying the debate.

However, I might not be able to resist the urge to jump in soon - but for now, just gritting my teeth, sucking it in and holding back.... Breath in, breath out, breath in, breath out.

Ahhhh, much better
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