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Astrophotography and Sketching >> Beginning and Intermediate Imaging

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kcgolden
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IC405 Data to play with. Feel free to try new
      #5526164 - 11/18/12 01:37 PM

I've uploaded a calibrated fits stack of somewhere around 30, 10 minute exposures shot with my ATIK 383L+ OSC through a WO 110 F/7 refactor using an orion skyglow imaging filter.

There is still a pretty bad gradient in the data. My processing was to do levels/curves iteration until I stretched it as far as I thought it would go and then apply the dust/scratches filter but this method seems to wash out the DSO while dimming the part of the image where the gradient is brightest.

Anyway, if anyone wants some data to play with, follow this link: Compressed IC405 RAR

Please post results and methods if you think you get something decent out of it.

UPDATE:

Here are the images, both scaled to 20% of original size. Before gradient removal:



And After:



Edited by kcgolden (11/18/12 06:09 PM)


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zerro1
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Re: IC405 Data to play with. Feel free to try new [Re: kcgolden]
      #5526247 - 11/18/12 02:29 PM

Thanks Kelsey
being very "sky deprived" this season I certainly appreciate the chance to do some post processing on something other than data I've about worn threadbare re-re-re-hashing


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kcgolden
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Re: IC405 Data to play with. Feel free to try new [Re: zerro1]
      #5526544 - 11/18/12 06:07 PM

No problem zerro1. I hope you get some decent results so you can tell me how you did it. :-). I've only had a permanent observatory for three years and have only been taking pictures for five+ and still can't process them at all.

I added images of my trouble spot to the original post for anyone that may have some advice to contribute about what I'm doing wrong.

Edited by kcgolden (11/18/12 06:08 PM)


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David Ault
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Re: IC405 Data to play with. Feel free to try new [Re: kcgolden]
      #5527033 - 11/18/12 11:00 PM Attachment (23 downloads)

Kelsey,

Thanks for posting your data. I really appreciate everyone that is brave enough to do that and give the rest of us a chance to learn from more than just our own data. The gradient did seem a little strong, but not impossible to work with and once removed the data seemed really good. I use PixInsight for processing and it's DynamicBackgroundExtraction process is fantastic for removing gradients, even compound ones. After that I used the ColorCalibration tool to balance out the colors. Then a did a light noise reduction before moving on to a masked stretch. This is a simplification of all the steps I took, so if you want more details just let me know.

Regards,
David

Here's my version:


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kcgolden
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Re: IC405 Data to play with. Feel free to try new [Re: David Ault]
      #5527546 - 11/19/12 09:38 AM

David,

Thanks for showing me what's possible! I was close to giving up and going back to a mono camera and narrowband but your processing gives me hope. I have not tried pixinsight but I definitely will after seeing what you were able to accomplish.


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kcgolden
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Re: IC405 Data to play with. Feel free to try new [Re: kcgolden]
      #5528027 - 11/19/12 01:52 PM

David,

I'm curious about the order of your steps. Did you do the gradient removal before or after stretching? Does it matter?


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zerro1
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Re: IC405 Data to play with. Feel free to try new [Re: kcgolden]
      #5528505 - 11/19/12 06:13 PM Attachment (10 downloads)

Hi Kelsey

My process was done completely in Photoshop CS3. After levels and curves, and a little color ballance adjustment using levels, I used gradient Xterminator plugin and HLVG plugin to combat the gradient. Then cropped the stacking artifacts off, and created a second layer. On the background I reduced the stars, then reduced the opacity of the upper layer to soften the stars and allow the nebulosity to show through. At the end I used Selective color adjustment to adjust to taste, and match color for intensity.

This is a tough target that really benefits from "many long subs".

Thanks for letting me have a go at it.


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Jb32828
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Re: IC405 Data to play with. Feel free to try new [Re: zerro1]
      #5528572 - 11/19/12 06:51 PM

I love other peoples data. Thanks for sharing, I will post my result soon.

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mikotoy
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Reged: 06/20/12

Re: IC405 Data to play with. Feel free to try new [Re: kcgolden]
      #5528580 - 11/19/12 07:00 PM

In PI, gradient removal happens before the permanent stretch. One would perform a temporary stretch to get an idea of where the gradients exist to carefully select the true representation of the background.

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kowspot2000
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Reged: 07/23/11

Loc: Corvallis, OR
Re: IC405 Data to play with. Feel free to try new [Re: Jb32828]
      #5528582 - 11/19/12 07:01 PM

Nice work!

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Jb32828
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Re: IC405 Data to play with. Feel free to try new [Re: kowspot2000]
      #5528745 - 11/19/12 08:32 PM Attachment (14 downloads)

Here's my attempt. That was some serious gradient, and I didn't really get it all, I did what I could and tried to make what I couldnt appear to blend in with the nebula...Processed in PixInsight. If you want the project file let me know, I saved the project with the history.

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David Ault
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Re: IC405 Data to play with. Feel free to try new [Re: Jb32828]
      #5531276 - 11/20/12 11:10 PM

Kelsey,

Sorry I didn't respond sooner. Lots of family in my house at the moment. As Mikotoy said, gradient removal should come before stretching. In fact I do as much processing as possible on the linear data. My last few steps typically go something like this:
- masked stretch - this is a script in PixInsight which compresses the dynamic range as it stretches
- maybe a few small non-masked stretchs or curve adjustments
- for color images I may make a slight adjustment to the color balance after stretching
- a pass of HDR and/or local histogram equalization (if I've done a masked stretch I rarely use the HDR tool).
- a final mild pass of noise reduction if still necessary, this may be applied to just the luminance or chrominance and usually the mask I use is very strict

I don't know that you need to give up on Photoshop. As others have shown it is very capable for astrophotography, especially with some of the plug-ins out there.

Regards,
David


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kcgolden
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Re: IC405 Data to play with. Feel free to try new [Re: David Ault]
      #5532094 - 11/21/12 11:52 AM

Thanks to all who have posted.

I was considering giving up on PS but then I saw the price of PixInsight and given that I've spent that much and more on PS and seeing that gradients have been removed, I'm inclined to try a little harder. I'll post results soon, especially if my employer dismisses everyone early today.


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jsines
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Re: IC405 Data to play with. Feel free to try new [Re: kcgolden]
      #5532131 - 11/21/12 12:11 PM

Your first picture up there needs a crop of the stacked images before you do anything else. You've got diagonal lines in the upper right corner, and probably some black areas where there were no images. You need a cropped, solid image before you do anything else. I see it in the second version, too. Those areas may negatively affect your levels, curves, and gradient removal. Just a suggestion.

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kcgolden
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Re: IC405 Data to play with. Feel free to try new [Re: jsines]
      #5532181 - 11/21/12 12:34 PM

Quote:

Your first picture up there needs a crop of the stacked images before you do anything else. You've got diagonal lines in the upper right corner, and probably some black areas where there were no images. You need a cropped, solid image before you do anything else. I see it in the second version, too. Those areas may negatively affect your levels, curves, and gradient removal. Just a suggestion.




It was just a lazy attempt but you could be right when it comes to dynamic tools like gradientXterminator or those in pixInsight. I was doing the gausian blur subtraction in PS though so any affect on the gradient would've been localized to those areas that needed to be cropped.


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kcgolden
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Re: IC405 Data to play with. Feel free to try new [Re: kcgolden]
      #5534544 - 11/22/12 10:16 PM

Here's my first major attempt in pix insight:



I was satisfied with the gradient removal but clearly, the feinter parts of the nebula could use more signal. This was already 30 stacked, 10 minute subs. I guess maybe I quit before I had enough data.

Maybe I need a bit more or would going with a longer exposure (say 15 minute) with the same number of subs do better?

Edited by kcgolden (11/22/12 10:18 PM)


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zerro1
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Re: IC405 Data to play with. Feel free to try [Re: kcgolden]
      #5534623 - 11/22/12 11:20 PM

Quote:

Maybe I need a bit more or would going with a longer exposure (say 15 minute) with the same number of subs do better?





Nice work!

Longer subs would probably help with the faint stuff. I've gone to 15 minutes "at a dark site" with my QHY9C (also an 8300 chip)and it made quite an improvement. certainly more subs is always better. If you have the oportunity to push for more subs even at 15 minutes...go for more subs.

PixInsight is a great program and I'm a huge fan but, it's a resource hog as well as being a good tool. If you don't have the hardware((RAM)and I don't) you can encounter out of memory issues that will frustrate the *bleep* out of a guy.


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kcgolden
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Re: IC405 Data to play with. Feel free to try new [Re: zerro1]
      #5535109 - 11/23/12 09:31 AM

I have run out of memory before on my 32-bit machine with 4gb of memory while processing a stack of around 100 exposures of the virgo cluster. With 64-bit machines becoming so common though, I expect those issues will be a thing of the past. I just wish EQMOD could run on MAC or Linux because those two OSs are much smarter with memory.

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David Ault
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Re: IC405 Data to play with. Feel free to try new [Re: kcgolden]
      #5535487 - 11/23/12 01:15 PM

Robert,

It's interesting that you've had memory problems with PixInsight. My experience has been entirely opposite. I've had problems with DSS running out of memory, but never PixInsight. My laptop is fairly old and only has 2GB of RAM (I am running 64-bit windows vista which already consumes 300+ MB of that memory). I've done some stacks as large as 200+ images from an ST-8300 (binned 1x1) without memory issues (it did take a long time), so I wonder if there is something else going wrong for you. As far as I can tell PixInsight is good at using as much resource as it is able, but not more. Not that I'm an expert in such things, all I do know is that I typically use DSS in the field to check my acquisition results and at a certain point it starts failing due to memory overuse at which point I switch over to PixInsight without any problems.

Regards,
David


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kcgolden
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Re: IC405 Data to play with. Feel free to try new [Re: David Ault]
      #5535804 - 11/23/12 04:06 PM

It's actually not your RAM that limits memory available to processes. The memory used by processes will actually overflow onto your hard drive when you run over the amount in RAM, which includes the memory used by your OS. This is called "paging" and what you'll see when this happens is a general slow down since your comp has to access memory from your HD which is slower, instead of RAM. You can actually speed up your computer by adding more RAM, up to a total of 4gb on a 32bit machine.

What can cause an Out Of Memory situation is either: the process limits itself to a certain memory footprint, or the footprint exceeds 4GB which is the maximum amount any one process can have on a 32-bit machine. On a 64-bit machine, the 4GB limit no longer applies but the process may still set some arbitrary limit on itself.

The lesson from this is you should aim for 4gb of RAM (the maximum) on a 32-bit machine to ensure that memory is rarely what slows you down. Second, on a 64bit machine, you should try to buy as much RAM as you can because the "maximum" is way too high for anyone to afford at this time, although windows 7 and 8 are setting arbitrary limits on this based on your "edition," because well, you know how they are. 8gb is what I would call a "minimum" for a 64-bit machine though.

If a process runs out of memory on a 64bit machine, it is more than likely the developer's fault, unless you don't have enough free hard drive space to accommodate paging.

Edited by kcgolden (11/23/12 04:33 PM)


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