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

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akulapanam
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Reged: 08/27/12

Re: Achieving color in galaxy shots new [Re: avarakin]
      #5666899 - 02/07/13 11:25 AM

Darks were taken on the same nights (15 each night) at the same temp as the light frames.

The links seem to work ok for me. Once you see the file in skydrive right click on them and click the download from the menu.


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pfile
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Reged: 06/14/09

Re: Achieving color in galaxy shots new [Re: akulapanam]
      #5667390 - 02/07/13 04:08 PM

by the way, i just noticed that the subexposure length is 40 seconds. i think you're at f/6.3, so you're not going to gather too much signal. i think that's the cause for the pattern noise i was seeing. you have to stretch the data so far that the bias pattern noise comes right to the front.

i'd suggest longer subexposures, unless you think you really had cleared the read noise. i can't download your links without creating a microsoft account, so i can't really tell.


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avarakin
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Reged: 07/13/09

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Re: Achieving color in galaxy shots new [Re: pfile]
      #5667641 - 02/07/13 06:42 PM

I normally shoot from red zone 30" at ISO1600 and F5.6 without filters and getting into desired area of histogram, so his exposure sounds right.
Alex


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srosenfraz
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Re: Achieving color in galaxy shots new [Re: akulapanam]
      #5667657 - 02/07/13 06:52 PM

Quote:


The links seem to work ok for me. Once you see the file in skydrive right click on them and click the download from the menu.




John -

It allows me to download the darks and the flats. But, when I try to download the Lights, it wants me to log in.

It probably works for you because you're already logged in. Try logging out (so that it sees you as a "public" person) and then try downloading. I don't think it'll work for you when you're not logged in - its not working for me.


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akulapanam
super member


Reged: 08/27/12

Re: Achieving color in galaxy shots new [Re: srosenfraz]
      #5667885 - 02/07/13 09:22 PM

Quote:

Quote:


The links seem to work ok for me. Once you see the file in skydrive right click on them and click the download from the menu.




John -

It allows me to download the darks and the flats. But, when I try to download the Lights, it wants me to log in.

It probably works for you because you're already logged in. Try logging out (so that it sees you as a "public" person) and then try downloading. I don't think it'll work for you when you're not logged in - its not working for me.




The issue seems to be that I can't share a file that large with someone without a skydrive account. I'll try and make it two smaller ones.


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akulapanam
super member


Reged: 08/27/12

Re: Achieving color in galaxy shots new [Re: akulapanam]
      #5668047 - 02/07/13 10:57 PM

Try this one.

http://sdrv.ms/XUuCjo


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srosenfraz
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Re: Achieving color in galaxy shots new [Re: akulapanam]
      #5668105 - 02/07/13 11:28 PM

Quote:

Try this one.

http://sdrv.ms/XUuCjo





That works - I can download that one. I'll probably give it a try tomorrow.


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srosenfraz
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Re: Achieving color in galaxy shots new [Re: srosenfraz]
      #5669894 - 02/08/13 10:25 PM

I did a quick processing on the sample data you posted. Obviously, the noise is very high since there's less than 3 minutes of total exposure and the data was captured from a red zone. As such, I was limited to how much I could stretch it and how much can be shown in the image. However, I think you can see that the galaxy's spiral arms have a blue color to them, while the core is heading towards a yellow/red color. These are typical colors I expect from M81.

When I compare it to your original image, it appears that your image lacks much of the blue, and the core is much redder than my processing of your 4x40 subs. Also, when I processed your original 32 bit Tiff, I had to push blue into the galaxy in order to have similar colors.

My gut suspicion is that there's something you're doing in your pre-processing that is altering the colors or removing some of the color. I'd be hard pressed to tell you what it is, but I didn't have to do anything fancy with my processing of the 4x40 subs to bring out blue in the galaxy.

If it'll help, here's the basic workflow I did with your data:

1) Used Images Plus 5.0 for automatic processing (generate master dark, generate master flat, convert CR2s to FITs, calibrate lights, normalize lights, align, and combine). This is a lot of steps, but IP does it all automatically after you point it to the data files.

2) Initial DDP stretch in Images Plus 5.0 - settings of Break Point 10,000, Background Weight .92, Scale function nth Root X^n, Root .820

The rest of the processing was in Photoshop CS5:

3) Gradient Xterminator

4) Levels - set initial grey point, set initial black point.

5) HLVG - Medium setting. Removes some of the green pixel noise.

6) Mild stretching curve

7) Carboni Deep Space Noise Reduction

8) Another mild stretching curve

9) Saturate using Block Method - 3 times

10) Levels - set final white and black points


Other than saturating and HLVG, there's nothing in this workflow that would have affected the color balance in the image (the HLVG would have taken out some green, so the image is very slightly more magenta). Certainly there's nothing here that would have pushed blue into the spiral arms.

I'm not sure if this is helpful, but hopefully it may give you some ideas about where to look for your lost color. Please let me know if you have any questions or thoughts.


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pfile
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Reged: 06/14/09

Re: Achieving color in galaxy shots new [Re: srosenfraz]
      #5669928 - 02/08/13 10:56 PM

btw i agree, i processed the image in PI and with enough saturation boost you can see the right colors, albeit very faint.

bottom line is that when i shot this at f/7 from a red zone, i had to do 10h of integration time to get a decent result. 3 minutes is just too short to expect much...


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akulapanam
super member


Reged: 08/27/12

Re: Achieving color in galaxy shots new [Re: pfile]
      #5669965 - 02/08/13 11:35 PM

Interesting it must be something in DeepSkyStacker because that is the only pre-processing I use. Any ideas?

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akulapanam
super member


Reged: 08/27/12

Re: Achieving color in galaxy shots new [Re: akulapanam]
      #5669973 - 02/08/13 11:46 PM

Here are my DeepSkyStacker settings:

Lights
Stacking Method: Kappa-Sigma Clipping
Per Channel Background Calibration

Darks
Median Kappa-Sigma Clipping
Hot Pixel Detection

Flats
Median Stacking Method

Result is set to "mosaic mode"


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srosenfraz
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Re: Achieving color in galaxy shots new [Re: akulapanam]
      #5670051 - 02/09/13 01:56 AM

I don't use DSS, so I probably won't have the greatest suggestions. There's lots of folks on the list that use DSS (probably more than any other program), so hopefully someone can take a look at your settings and make suggestions.

The one thing about which I would wonder in your settings is the "Per Channel Background Calibration". Not knowing what it does, perhaps that could be related? Is this a default setting? Also, I've heard folks talk about issues with Deep Sky Stacker doing a screen stretch and if you save the file incorrectly, it'll use the screen stretch and create some color problems.

Again, I haven't used DSS, so I'm just speculating that perhaps there's something within that issue could be related to your color issue.


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srosenfraz
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Re: Achieving color in galaxy shots new [Re: pfile]
      #5670058 - 02/09/13 02:00 AM

Quote:

btw i agree, i processed the image in PI and with enough saturation boost you can see the right colors, albeit very faint.

bottom line is that when i shot this at f/7 from a red zone, i had to do 10h of integration time to get a decent result. 3 minutes is just too short to expect much...





Just to be clear - akulapanam had indicated in his original post that his image was made from about 2 1/2 hours of integration. The 3 minutes of subs he posted here was just because of the constraints of trying to transfer raw data over an internet connection.

Also, I'm glad to hear you saw similar results when processing in PI - I think it confirms that there is actually useful color in the data.


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pfile
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Reged: 06/14/09

Re: Achieving color in galaxy shots new [Re: srosenfraz]
      #5670945 - 02/09/13 03:55 PM

oh sorry, i got confused... as usual.

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akulapanam
super member


Reged: 08/27/12

Re: Achieving color in galaxy shots new [Re: pfile]
      #5671137 - 02/09/13 06:03 PM

I switched it to the RGB option instead of the Per Channel and it didn't have an effect :-( See below

http://sdrv.ms/Y1MeYV


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pfile
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Reged: 06/14/09

Re: Achieving color in galaxy shots new [Re: akulapanam]
      #5671595 - 02/09/13 11:35 PM

do you have 'set black point to zero' checked? that was the culprit in someone else's data that i was looking at recently.

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akulapanam
super member


Reged: 08/27/12

Re: Achieving color in galaxy shots new [Re: pfile]
      #5671674 - 02/10/13 12:32 AM

No I double checked that and I played around with white balance on the same page without any results.

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akulapanam
super member


Reged: 08/27/12

Re: Achieving color in galaxy shots new [Re: akulapanam]
      #5673122 - 02/10/13 09:38 PM

Scott if you don't mind try this file out and see if you can do anything with it. It is looking a little better to me. I used imagemagick to get around the dss saving issue and I switched dss to standard mode from mosaic. The mode shouldn't make a difference but it might help.

http://sdrv.ms/154NAcz


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mmalik
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Re: Achieving color in galaxy shots new [Re: akulapanam]
      #5673539 - 02/11/13 06:48 AM Attachment (15 downloads)

My go at your AS2 data...

Processing Workflow: (Instructions here...)
•Crop in ImagesPlus 5.0
•Digital Development in ImagesPlus 5.0
•Multi Point Flatten Background-Planar in ImagesPlus 5.0
•Multiresolution Smooth-Sharpen (Finest/Fine 40/20) in ImagesPlus 5.0
•Geometric Transform/Scale (Factor 0.5) in ImagesPlus 5.0
•Smoothing in ImagesPlus 5.0
•Saturation (Block I), and 'Noise Reduction' in Photoshop Extended CS6
•Star Size and Halo Reduction in ImagesPlus 5.0
•Hue-Saturation-Luminance in ImagesPlus 5.0
•Saturation (Block II), Curves, Contrast, and Saturation in Photoshop Extended CS6


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Dave Venne
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Reged: 11/12/07

Loc: Burnsville, MN, USA
Re: Achieving color in galaxy shots new [Re: akulapanam]
      #5674544 - 02/11/13 05:58 PM Attachment (6 downloads)

Your image has some real difficulties with the background--light pollution and some vertical banding is making it very uneven. But there is enough signal to produce some reasonable color--as Scott's quick processing showed. Here's Mikes image, with some judicious channel mixing. I'm not entirely happy with the tinge of the background, but the galaxy center has a rosier glow and the spiral arms are bluer, both of which resemble the colors found by much better imagers than myself.

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