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M27- Resurrected with PI

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#1 bluedandelion

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Posted 07 April 2013 - 10:47 PM

M27 the Dumbbell nebula in Vulpecula, captured with a Canon 350D and a C9.25 at f/10, 24 exposures of 5 min duration for a total of two hours collected over two nights in 2009 from my red zone backyard.

Color is very difficult on this target. Did I go overboard? Comments welcome.

Posted Image
Higher res at 2x2 bin

Below is the old version done in 2009, I believe.
Posted Image

Ajay

#2 bluedandelion

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Posted 11 April 2013 - 08:45 PM

Well the silence tells me, the answer is, "Yes!"

Well how about this one? Less saturated, less red.

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http://www.flickr.co...25137/lightbox/

Ajay

#3 mmalik

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Posted 11 April 2013 - 09:13 PM

Ajay, image link in your first post seems broken; see if you can fix. Thx

#4 Nils_Lars

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Posted 12 April 2013 - 12:00 AM

I think you got more detail from the PI version but I like the soft teals and reds of the original , M27 can be surprisingly tough to process.

#5 bluedandelion

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Posted 12 April 2013 - 12:14 AM

Mike, I think the first version was way over saturated. I tried an LLRGB process. Separated out the lightness and worked on it to get enhance details. Then I combined it with the LRGB. Now in PI you can push both the L and the LRGB while you combine them. I think I over did that step.

So the second time around, I did not push the saturation while combining. I did use curves to boost saturation later.
I deleted the image at the first link. Unfortunately I cannot edit my post any more.

Erik, The soft teal was done inelegantly and as you can see the effect on other parts of the image is quite drastic - clipped back ground, no star color etc.

Appreciate the feedback.

Ajay

#6 Magellan

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Posted 12 April 2013 - 08:35 AM

can you detail your process for LLRGB in PI, I have always wanted to try it on some of my images.

#7 jsines

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Posted 12 April 2013 - 11:13 AM

I extract the Luminance layer and don't do anything to it. Then I reapply it using LGRB. I uncheck the R,G,B. I lower the Saturation to 0.25 and check chrominance noise reduction. For me on DSLR images, this usually brings out the colors more and reduces the noise. After this step I reset the black point again with histogram transform.

#8 Magellan

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Posted 12 April 2013 - 11:41 AM

very cool, I am going to try this. I assume that you are working with images in linear form?

The only option I have is Extract CIE L* (lightness) not CIE Y (Luminance) When I extract lightness and run LGRB combine unchecking RGB, it tells me it can't run on grayscale images.

#9 bluedandelion

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Posted 12 April 2013 - 07:59 PM

This was an experiment. I had 8x5 min darks for one night and only 4x 5min darks for the second night. So my hope was to try and do some noise mitigation steps on the LRGB, bring out details in the L component and then combine the two. It worked nicely .

* After calibration, registration, integration and running DBE, I extracted the lightness component (CIE L*). This is what I referred to as L. The original image is the LRGB image.

* Did Atrous Wavelet Noise reduction on both L and LRGB.

* Did a custom Richardson Lucy Deconvolution on the L component: http://www.manuelj.c...1767553866&a...

* Individually stretched and did HDR Multiscale transform on each component.

* Combined components after this step, using the usual LRGB combination procedure. For the latest M27 image I set the midpoint of the L histogram at 48 and that of the LRGB at 43 during combination to get a boost in saturation. Here's a link to Harry's Tutorial on this step: http://www.harrysast...d.com/lrgb.HTML

* Morphological transformation to reduce star size. If you do this on the L and LRGB components separately, make sure you use the same setting or you could end up with halos.

* Local Contrast Enhancement. If you do LHE without star size reduction, the large bright stars will be too bold.

* From this point on do whatever processing you usually do. I did a little more saturation boost, slight tweak to the color, 2x2 binning and then some Unsharp Mask.

Hope this helps. I hope to try similar steps on other images soon.

Ajay






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