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Astrophotography and Sketching >> DSLR & Digital Camera Astro Imaging & Processing

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Falcon-
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Dim Dust Data Chalenge! Try my NGC7023 @300mm?
      #5719791 - 03/08/13 02:12 AM

I have now spent a couple of nights processing and re-processing (and re-re-processing) a shot of the Iris Nebula I captured back in September 2012 and am only now getting around to working on.

I think I finally have something I am ok with - but found it VERY hard to process and wanted to inflict... er... offer the data to the forum to see how others here might manage the same data. It has often been quite instructive to see the varying interpretations and techniques!

So first off - the raw stacks as they came out of the PixInsight ImageIntegration process both in PI's native format and a more accessible 16bit TIFF:

- NGC7023-Tair3s_24x600s.fit.zip (32bit floating-point FITS file, 96M zipped)
- NGC7023-Tair3s_24x600s_16bit.tif.zip (16bit uncompressed TIFF, 37M zipped)

Next post will be my take on the data.

Enjoy!


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Falcon-
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Re: Dim Dust Data Chalenge! Try my NGC7023 @300mm? new [Re: Falcon-]
      #5719792 - 03/08/13 02:21 AM Attachment (51 downloads)

Here is my take on... er... my own Iris data.

My two main conclusions are that I need more time and I should have run at f/6.7! The light pollution gradients did not make processing easier either so I guess a visit to a TRUE dark site would help too..

NGC7023 Widefield:
- Scope: Tair-3s camera lens (300mm f/4.5) @ F/8
- Camera: Canon XS/1000D (not modified)
- Mount: Celestron CI-700
- Guide: 50mm finder, SSAG
- Filters: none
- Software: BackyardEOS for capture, PixInsight for calibration and processing
- Exposure details: 24x 600s exposures (4 hours) @ ISO1600

High resolution version available on my site here


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mmalik
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Re: Dim Dust Data Chalenge! Try my NGC7023 @300mm? new [Re: Falcon-]
      #5719812 - 03/08/13 03:01 AM

Quote:

I need more time and I should have run at f/6.7! The light pollution gradients did not make processing easier either so I guess a visit to a TRUE dark site would help too..




Plus I think field is quite wide. Nice attempt though. Mine up close.... Thx


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Mike Clemens
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Re: Dim Dust Data Chalenge! Try my NGC7023 @300mm? new [Re: Falcon-]
      #5719814 - 03/08/13 03:03 AM

Looks really nice. That's a great lens evidently, it looks like an excellent capture.

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fco_star
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Re: Dim Dust Data Chalenge! Try my NGC7023 @300mm? new [Re: Mike Clemens]
      #5720012 - 03/08/13 08:33 AM

Falcon, your Tair is a winner, great job!

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Falcon-
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Re: Dim Dust Data Chalenge! Try my NGC7023 @300mm? new [Re: mmalik]
      #5720376 - 03/08/13 11:56 AM

Quote:

Quote:

I need more time and I should have run at f/6.7! The light pollution gradients did not make processing easier either so I guess a visit to a TRUE dark site would help too..




Plus I think field is quite wide. Nice attempt though. Mine up close.... Thx




Nice job on your close up. I have a slightly less close up version from a couple years ago here.

However the wide field in this attempt and the "Dim Dust Data Chalenge" thread title are no coincidence. What I was trying to capture here is the outer dark nebulosity associated with the Iris.

Check out this picture google image search found me showing the extend of the.... It also better shows the smaller Ghost Nebula (barely visible in the top-right in my image). If I had known about that when I started imaging I may very well have re-framed slightly.


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Falcon-
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Re: Dim Dust Data Chalenge! Try my NGC7023 @300mm? new [Re: Falcon-]
      #5720384 - 03/08/13 11:59 AM

Thanks Mike, thanks Francisco

With regards the Tair it does do fairly well - however I several passes of star reduction here to get this result. I also seem to have an odd issue with slightly off-round stars that I *think* is in the lens but an unsure. It is not bad, but it is present.


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srosenfraz
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Re: Dim Dust Data Chalenge! Try my NGC7023 @300mm? new [Re: Falcon-]
      #5721434 - 03/09/13 12:15 AM

Your image looks great, Sean. Nice star colors, lots of dust and good contrast with the dark nebulae.

Your data looked too interesting to pass up, so I decided to try a quick process on it.





I agree with you that it could use some more time. I pushed the data pretty hard (probably harder than I should have). Also, because I didn't want to spend too much time on it, I reduced the resolution early on. So, I lost a lot of detail potential with that.

Anyway, thanks for the processing challenge - it definitely was that!


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Nils_Lars
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Re: Dim Dust Data Chalenge! Try my NGC7023 @300mm? new [Re: srosenfraz]
      #5722749 - 03/09/13 06:09 PM

Id say you did very well with it and I cant believe you were able to pull out that much dust at f/8.

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Falcon-
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Re: Dim Dust Data Chalenge! Try my NGC7023 @300mm? new [Re: Nils_Lars]
      #5725167 - 03/11/13 03:15 AM

Thanks for your take Scott. What software did you use? I am not sure how you managed to keep the stars down to such a low level while still bringing dust out!

Erik: Of course it does not match the unrealistic expectations I had in the back of my mind during capture, but ya, considering conditions and f/8 the data does at least contain the dust! Does make me wish for true-dark skies and f/4 optics though!


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Falcon-
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Re: Dim Dust Data Chalenge! Try my NGC7023 @300mm? new [Re: Falcon-]
      #5725177 - 03/11/13 03:27 AM Attachment (17 downloads)

Scotts comment about "reducing the resolution early" got me to thinking.... so I re-stacked the images using SuperPixel debayer rather then VNG debayer. 1/4th the total resolution but I think the reduction in chrominance and luminance noise seems to have been worth it in this case.

I also discovered part of why I had such trouble with colour calibration.... It seems during debayer PixInsight was scaling the 12bit raw data to fill the full 32bit working space (logical). HOWEVER it was doing that ONLY for the first channel (Red in this case) leaving Blue and Green "missing" data entirely in the top of the dynamic range! I simply clipped the white point on both blue and green channels till at least one pixel was 100% intensity and the starting colour balance was closer to sane then usual. Still in need of adjusting, but better then last time!

Anyway... Here is a 50% resolution (slightly cropped) version of my re-process. I am happier with this result for sure. None the less this is obviously pushing the data a bit past where it should be - just not enough signal and too much noise in the dim data. I also re-uploaded the version on my gallery so the higher-res version can be found here.


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Falcon-
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Re: Dim Dust Data Chalenge! Try my NGC7023 @300mm? new [Re: Falcon-]
      #5725181 - 03/11/13 03:29 AM

Curses! The re-upload changed the URL and edit time as expired on my original post. Alas the link in the second post of this thread is now a dud.


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srosenfraz
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Re: Dim Dust Data Chalenge! Try my NGC7023 @300mm? new [Re: Falcon-]
      #5726787 - 03/11/13 08:26 PM

Quote:

Thanks for your take Scott. What software did you use? I am not sure how you managed to keep the stars down to such a low level while still bringing dust out!





Mostly I use a combination of Photoshop CS5 and Images Plus 5.0. As far as the star sizes and the dust - there's a few techniques I use. Keep in mind that I processed this as an LRGB image, where I create a synthetic luminance from a greyscale of the RGB. That helps to minimize effects from chromatic noise.

One of the things I do is that as I stretch the dust, I ONLY stretch that range. In other words, most of my curves set a few anchor points at and below the black point, and then will set an anchor point at the brightness of the dim dust. I'll raise that part of the curve and then I'll set a couple of anchor points above the faint dust and bring them back down to the diagonal line. This makes it so that the stretching applies to the dust and minimally to the stars. When I'm all done, I end up having a curve that is basically a diagonal line with a hump around the range of the dust.

The other thing that helps bring out the dark lanes is to set points at the dark lane and at the faint dust. Then, just lower the dark lane anchor point VERY little (usually an adjustment of just 1 will make a very dramatic difference). This steepens the curve between these two points, which increases the contrast between them. Then, again, I set anchor points below this and above this to make the curve ONLY affect this range.

Still, the stars and their halos will end up growing a bit, despite my best efforts. With a field of view like this that has so many stars, the nebula and dust shows a lot better if the stars are kept to a minimum. In order to combat the growth of the stars, I'll shrink the stars at several steps as I'm stretching (i.e., stretch, stretch, shrink... repeat as needed).

For star shrinking, the very best tool I've found is IP's Special Functions | Star Size and Halo Reduction. It does a great job shrinking the stars while leaving them looking natural and not affecting the rest of the surrounding images. If you don't have IP, then Carboni's Star Shrinking action works well, as can using the minimum filter and masking it to the stars. The beauty of IP's Star shrinking is that it affects ALL of the stars - even the fainter ones that tend to start overwhelming the image as you stretch them.

Hope this helps.


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srosenfraz
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Re: Dim Dust Data Chalenge! Try my NGC7023 @300mm? new [Re: Falcon-]
      #5726794 - 03/11/13 08:30 PM

Your reprocess looks really good, Sean. It shows all the dust very well. I agree with your decision to push the data too hard - it makes it noisier, but I think its a worthwhile compromise with this image, as the dust IS the subject. In a perfect world, you'd capture more data. But, sometimes we have to work with what we have.

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bluedandelion
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Re: Dim Dust Data Chalenge! Try my NGC7023 @300mm? new [Re: srosenfraz]
      #5737167 - 03/16/13 08:27 PM

Here's my attempt. This is a center crop of the 2x2 binned image. Jpeg compression really makes it ugly. If I receive permission from Sean,I will upload the full image to my Flickr account.

Edit: Whoops, forgot to attach the image! Here it is...



Ajay

Edited by bluedandelion (03/16/13 08:28 PM)


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Falcon-
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Re: Dim Dust Data Chalenge! Try my NGC7023 @300mm? new [Re: bluedandelion]
      #5742165 - 03/19/13 01:39 AM

Quote:

If I receive permission from Sean,I will upload the full image to my Flickr account.




Permission granted! Looking forward to seeing your non-JPEG-murdered version

In fact, to make it properly official for everyone I now declare that the two stacks linked from the first post here are released under a Creative Commons Licence.


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bluedandelion
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Re: Dim Dust Data Chalenge! Try my NGC7023 @300mm? [Re: bluedandelion]
      #5742171 - 03/19/13 01:46 AM

So with Sean's permission, below are the larger versions on Flickr.

Medium res in Light Box: http://www.flickr.com/photos/ajynrynn/8570216451/in/photostream/lightbox/

Full Size: http://farm9.staticflickr.com/8229/8570216451_4370d1e3fa_h.jpg

All processing was done with Pixinsight.

Ajay


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fco_star
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Re: Dim Dust Data Chalenge! Try my NGC7023 @300mm? [Re: bluedandelion]
      #5742364 - 03/19/13 07:19 AM

wow... love the TAIR lens...all are great results!

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shawnhar
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Re: Dim Dust Data Chalenge! Try my NGC7023 @300mm? [Re: fco_star]
      #5744280 - 03/19/13 11:33 PM Attachment (11 downloads)

Dim dust challenge accepted! Thanks for posting your data!
Ok, so I lost the Iris detail... but it sure was fun trying.


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Falcon-
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Re: Dim Dust Data Chalenge! Try my NGC7023 @300mm? new [Re: shawnhar]
      #5745979 - 03/20/13 07:04 PM

Ajay:

Ok... PLEASE share with me your colour calibration steps! The star, nebula and dust colours look much better in yours then my attempts. I know you started with the same data and use the same app so it must be my processing....

You also managed to bring out an impressive amount of detail in the Iris itself.


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