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

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ICallHimGamblor
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Reged: 06/24/13

I am doing something very very wrong
      #6118829 - 10/05/13 11:01 AM

For some reason, I can't ever extract useful data from my stacked images. Last night, I took three hours of lights of Stephan's Quintet (60x180sec ISO400). I took 20 darks, I have 25 flats and 15 biases, and still can only raise the cluster just barely above the image floor. I have a two-hour stacked image of the fireworks galaxy (NGC 6946) that I can't raise above a wisp of a hint of an image.

I thought I was using StarTools improperly, but this is what Ivo said: "This is not really something that's a post-processing problem that ST can deal with. It seems like a stacking problem (incorrectly applied flats/darks/bias) or possibly an acquisition problem."

I am using a LP filter and am dithering using BackyardEOS + PHP.

Here is the stacked image: http://www.astrobin.com/58749/

And here is a random sub: http://www.astrobin.com/58912/

Can someone do an autopsy on this image to figure out what I am doing wrong?

Thanks.


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Chris_H
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Re: I am doing something very very wrong new [Re: ICallHimGamblor]
      #6118875 - 10/05/13 11:28 AM

I think you are expecting too much at this focal length. You are also slightly out of focus which doesn't do you any good at all at this image scale (fine detail will be lost). Can't help you with startools though as I don't use it. But if it has levels and/or curves (and it should if it's made for astro!), I would play with them.

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mmalik
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Re: I am doing something very very wrong new [Re: ICallHimGamblor]
      #6118886 - 10/05/13 11:34 AM

If your sky allows, do 5 or 10min subs; raise the ISO to 800 or 1600. As a control test, do an ICNR in case you problem might be calibration. Use this... LPS filter if using something else. Get evals of ImagesPlus and PixInsight to stack and process, for comparison. Thx

Edited by mmalik (10/05/13 11:36 AM)


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srosenfraz
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Re: I am doing something very very wrong new [Re: mmalik]
      #6119064 - 10/05/13 01:39 PM

It looks like both your stacked image and your raw sub have had a stretch applied to them. It would be helpful to see the unstretched of each. Perhaps you could upload to someplace like Dropbox a raw sub (.CR2 file), as well as an unstretched 16 bit tiff?

You didn't mention what software you're using for stacking and calibrating. If you're using DSS, you'll want to save your final stack as a 16 bit tiff and be SURE that its not applying a screen stretch. You can tell if this is done correctly (unstretched), because the stacked tiff should be VERY dark (background 8 bit levels typically less than 5).

If you can post those two files, we'll probably have a better idea what you have happening.

Also, can you tell us more about ALL of the details about this image - what camera, is it modded, what scope (aperture and f/ratio), sky conditions (urban, rural, Bortle scale, Color zone, or SQM reading - some indication of how dark your sky is), what software you are using for stacking and calibration.


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ebacon
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Re: I am doing something very very wrong new [Re: srosenfraz]
      #6119168 - 10/05/13 03:12 PM

Will an unmodded camera detect Stephan's Quintet? At mag 14.8 it seems like it would be down in the noise.

I also shoot with an unmodded camera. I am in a red zone (according to Dark Sky Finder) and have found that many DSOs barely scratch through the noise floor.


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srosenfraz
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Re: I am doing something very very wrong new [Re: ebacon]
      #6119177 - 10/05/13 03:18 PM

Modding a camera increases the red sensitivity and has little (or no effect) at the blue end of the spectrum. Most galaxies tend to be either blue or white/yellow in general color, so they usually respond well to unmodded cameras. You typically won't capture the Ha regions very well, but the majority of the galaxy is unaffected.

The galaxies in Stephan's Quintet are mostly blue and yellow, so one would expect an unmodded camera to work almost as well as a modded camera for a target like this.

Ojbects that are primarily Ha (very red) benefit significantly from modding the camera.


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TimN
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Re: I am doing something very very wrong new [Re: srosenfraz]
      #6119366 - 10/05/13 05:30 PM

I don't think there is enough data there. I agree with Mikes earlier comment - bump up the iso to 800 and try at least 5 minute subs.

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ICallHimGamblor
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Re: I am doing something very very wrong new [Re: srosenfraz]
      #6119383 - 10/05/13 05:45 PM

Quote:

It looks like both your stacked image and your raw sub have had a stretch applied to them.




I have not stretched anything... those are the pics directly from the camera and DSS converted to JPG.

I am not sure what that tell you.


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ICallHimGamblor
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Re: I am doing something very very wrong new [Re: mmalik]
      #6119389 - 10/05/13 05:49 PM

Quote:

If your sky allows, do 5 or 10min subs; raise the ISO to 800 or 1600.




I thought I read somewhere on here that subs should have a histogram that lies at 1/3 of the histogram graph. If I can go further than that, I would love to, but the histogram on the sub I posted looks right on that point. Let me know if I can go further...


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ICallHimGamblor
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Re: I am doing something very very wrong new [Re: Chris_H]
      #6119392 - 10/05/13 05:50 PM

Quote:

I think you are expecting too much at this focal length.




Oh yeah... I am also using the standard celestron focal length reducer, so I am shooting at 6.something...


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Jamienite
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Re: I am doing something very very wrong new [Re: ICallHimGamblor]
      #6119409 - 10/05/13 06:02 PM

I agree with the above comments, 180 seconds is not enough for such a dim object. I've tried the quintet on a night where I wasn't tracking well and could only manage 2-3 minutes. I got results very similar to yours.

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Jamienite
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Re: I am doing something very very wrong new [Re: Jamienite]
      #6119420 - 10/05/13 06:09 PM

Oh, and bump up to iso800 for sure.

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shawnhar
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Re: I am doing something very very wrong new [Re: Jamienite]
      #6119445 - 10/05/13 06:29 PM

Restack the subs
In DSS, save picture to file, in the save options, make sure "Embed but DO Not apply" option is checked.
Upload that tiff to Dropbox or something we can download from
You might be surprised...


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srosenfraz
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Re: I am doing something very very wrong new [Re: ICallHimGamblor]
      #6119476 - 10/05/13 07:01 PM

Quote:

Quote:

It looks like both your stacked image and your raw sub have had a stretch applied to them.




I have not stretched anything... those are the pics directly from the camera and DSS converted to JPG.

I am not sure what that tell you.




I understand that you haven't consciously stretched anything - you probably have software doing it without you realizing it. From the camera, if you pull it into most software as a RAW, it'll apply a default stretch to it. When you save it as jpeg, it'll include that stretch. If you take it from the camera as a Jpeg, the camera will have applied the default stretch.

With DSS, the default behavior is to apply the screen stretch unless you tell it to save it as a 16 bit tiff and do NOT save the screen stretch with it. That's what it looks like you have there. Again, an unstretched image is usually VERY dark.

It would be quite valuable to see unstretched data, as you're asking about what you may be doing wrong to end up with less than optimal results. With unstretched data, we can look at it, process it, etc. to have a much better idea what the potential is.

With 3 hours of Stephan's Quintet, I would expect that you should normally have quite usable data. But, 3 hours is usually plenty enough time to have a good enough SNR to allow for a quality image - particularly at f/6.3. My image of Stephen's Quintet at f/6.3 on a C8 should be pretty comparable to yours. Mine was at ISO 1600, yours at ISO 400 - No big deal. If I had shot this at ISO 400, it would have looked more or less the same. I used 3 minute subs as well, and have a little over twice as much time. That means that my SNR is about 1.5x better than yours. That's better, but its not night and day either.

I suspect there's a decent image hidden in your data....

Edited by srosenfraz (10/05/13 07:06 PM)


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ICallHimGamblor
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Re: I am doing something very very wrong new [Re: srosenfraz]
      #6119502 - 10/05/13 07:27 PM

Wow... I had no idea stretching was being applied to my image.

Here is the 'no adjustments' version.

http://www.astrobin.com/58959/


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srosenfraz
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Re: I am doing something very very wrong new [Re: ICallHimGamblor]
      #6119514 - 10/05/13 07:37 PM

That looks like the right stuff. The only thing is that we need that as a 16 bit tiff. I don't think you'll be able to post that large a file to Astrobin - that's why the suggestion to use something like Dropbox (free for up to 2 GB of total storage).

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Jamienite
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Re: I am doing something very very wrong new [Re: srosenfraz]
      #6119531 - 10/05/13 07:49 PM

Wow! I had now idea about this dss auto stretch. Thanks Scott. Also, looking at your Quintet image, I see that 3 minutes is plenty of exposure! Great image!

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ICallHimGamblor
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Re: I am doing something very very wrong new [Re: Jamienite]
      #6119542 - 10/05/13 07:56 PM

Here is the TIF: https://docs.google.com/file/d/0By0hG91nGRL9aFZQVWlOSmJDakU/edit?usp=sharing

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srosenfraz
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Re: I am doing something very very wrong new [Re: Jamienite]
      #6119549 - 10/05/13 08:04 PM

Quote:

Wow! I had now idea about this dss auto stretch. Thanks Scott. Also, looking at your Quintet image, I see that 3 minutes is plenty of exposure! Great image!




Thank you very much. And you're welcome. Also, thanks to Shawn for the precise directions on how to save it correctly out of DSS.

One thing to note about the unstretched data - if you data is underexposed (i.e. ISO 400 with 3 minute subs from a dark sky), it can often be difficult to stretch this data using levels and curves (it can be done, its just very tricky). For these types of images, stretching with DDP (Digital Development Processing) tools makes all the difference in the world (as well as for well exposed images, too). For well exposed images (back of the camera histogram mountain well histogram well separated from left axis), stretching with levels and curves is the same as usual.


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mmalik
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Re: I am doing something very very wrong new [Re: ICallHimGamblor]
      #6119588 - 10/05/13 08:30 PM Attachment (23 downloads)

There seem to be calibration/gradient issues with your image. My go at your TIF below:

ImagesPlus:
1. RAW File Conversion (Skipped)
2. Align TSR/Combine/Crop (Only Crop)
3. Digital Development
4. Multi Point Flatten Background-Planar
5. Multiresolution Smooth/Sharpen
Saved as 16 bit TIFF for processing in PixInsight

PixInsight:
6. HDR Multiscale Transform
7. ACDNR (Noise Reduction)
Saved as 16 bit TIFF for processing in ImagesPlus/Photoshop

ImagesPlus/Photoshop:
8. Geometric Transform/Scale [0.3] (ImagesPlus [Skipped])
9. Smoothing & Noise Reduction (ImagesPlus)
10. ProDigital ‘Deep Space NR’ and HLVG (Photoshop)
11. Saturation (Block: 1 pass) and Noise Reduction (Photoshop)
12. Star Size & Halo Reduction, and Saturation (ImagesPlus)
13. Levels, Curves, Contrast, Brightness, Vibrance, and Color Balance (Photoshop)
Saved as JPG for posting


Processing instructions here...

Edited by mmalik (10/05/13 08:35 PM)


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srosenfraz
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Re: I am doing something very very wrong new [Re: mmalik]
      #6119911 - 10/06/13 12:52 AM

I agree with Mike about there being something wrong with this data. I have the same color gradient issues when I try to do a DDP stretch, and the image has extremely low contrast.

You've fundamentally done all the right things - captured a good amount of data, have reasonable number of calibration frames, etc. It feels like something may have gone haywire along the way.

A few questions -

1) With your flats - is the orientation of the camera unchanged from the time you take your flats until the time you start capturing?

2) When you captured your flats, did you have the CLS filter in place (and left it the same until you were capturing data)?

3) When applying your calibration frames in DSS - are you sure you have all of the correct frames in the right place (i.e., you didn't swap dark frames for flats, or some other type of mistake)?

4) Would you mind posting one raw .CR2, your Master Bias, Master Flat, and Master Dark frames?


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ebacon
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Re: I am doing something very very wrong new [Re: srosenfraz]
      #6120151 - 10/06/13 07:53 AM

I am learning from this thread, too.

What are calibration frames? Is that a generic term for the groups of flats, bias, and darks?

Thanks!


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Footbag
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Re: I am doing something very very wrong new [Re: ebacon]
      #6120250 - 10/06/13 09:29 AM

Quote:

I am learning from this thread, too.

What are calibration frames? Is that a generic term for the groups of flats, bias, and darks?

Thanks!




Yes. Flats, darks and bias are calibration frames.


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shawnhar
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Re: I am doing something very very wrong new [Re: Footbag]
      #6120513 - 10/06/13 12:23 PM Attachment (8 downloads)

I'm gonna guess one of 2 things....
1st, this image was taken through clouds, maybe high thin clouds you couldn't see, but that is the most likely case. I have had the same thing happen, flat's can't fix it because the gradients are changing frame to frame.
2nd and hopefully less likely, you have crazy multiple light sources around like neighbor lights or you are shooting through/close to light sources. Flats can't fix that either because the target is moving, therefore the gradients are moving frame to frame.
I gave a go in Star Tools but like Ivo said, very difficult to doa anything with it in post processing, those gradients are pretty rough. I tried using masks for the galaxies and "isolate" in the Life function.


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petemumbower
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Re: I am doing something very very wrong new [Re: shawnhar]
      #6120651 - 10/06/13 01:56 PM

How does the each frame look after calibration before stacking? I want to agree that maybe high thin clouds are present.

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Tonk
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Re: I am doing something very very wrong new [Re: petemumbower]
      #6120689 - 10/06/13 02:18 PM

Quote:

I'm gonna guess one of 2 things....
1st, this image was taken through clouds, maybe high thin clouds you couldn't see, but that is the most likely case. I have had the same thing happen, flat's can't fix it because the gradients are changing frame to frame.
2nd and hopefully less likely, you have crazy multiple light sources around like neighbor lights or you are shooting through/close to light sources. Flats can't fix that either because the target is moving, therefore the gradients are moving frame to frame.
I gave a go in Star Tools but like Ivo said, very difficult to doa anything with it in post processing, those gradients are pretty rough. I tried using masks for the galaxies and "isolate" in the Life function.




1 thing wrong here and a solution

1) Flats are never to be used to correct for sky gradients - what you are describing is not a optical transmission issue so flats are totally inapropriate

2) The correct way to correct external gradients is to use a subtractive process using tools such as Russel Croman's GradientXTerminator or one of the Background Extraction tools found in PixInsight or Images Plus.

The fact that the gradients change during the imaging session is immaterial as the correction is performed on the final stacked image, usually right after the initial stretch

I suggest you read Russel's tutorial to gain an understanding of what needs to be done

http://www.rc-astro.com/resources/GradientXTerminator/tutorial.html

As I said there are a selection of astro-image processing applications that provide specific solutions


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ICallHimGamblor
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Re: I am doing something very very wrong new [Re: srosenfraz]
      #6120899 - 10/06/13 04:23 PM

Quote:


A few questions -

1) With your flats - is the orientation of the camera unchanged from the time you take your flats until the time you start capturing?

2) When you captured your flats, did you have the CLS filter in place (and left it the same until you were capturing data)?

3) When applying your calibration frames in DSS - are you sure you have all of the correct frames in the right place (i.e., you didn't swap dark frames for flats, or some other type of mistake)?

4) Would you mind posting one raw .CR2, your Master Bias, Master Flat, and Master Dark frames?




Thanks for continuing to help diagnose this. To answer your questions:

(1) The camera orientation had not changed.
(2) The LP filter was in place for the flats as well as the images. I'm hoping CLS filter=LP filter
(3) I am pretty sure I put the calibration frames in the right place, but I will check again.
(4) I have added the calibration frames and a random sub to this folder: https://drive.google.com/folderview?id=0By0hG91nGRL9ckxUeXAxUXdTLTQ&usp=s...

Let me know if that doesn't give you the access you need.

Since there is such an emphasis on my flats, I will explain what I did to capture them... They are t-shirt flats captured in the early evening before an imaging session. I had the camera on manual and used BackyardEOS to capture them and I tweaked the exposure time until the histogram was approx halfway. That's how a couple threads on this site said to make them.

I hope I'm not embarrassing myself with my noob-ness.

Thanks everyone for y'alls help.


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ICallHimGamblor
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Re: I am doing something very very wrong new [Re: shawnhar]
      #6120905 - 10/06/13 04:28 PM

I would be surprised if it was a high-clouds issue. I have this problem with every imaging set I have ever taken, including four different nights over the past week or so on different targets.

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mmalik
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Re: I am doing something very very wrong new [Re: ICallHimGamblor]
      #6120917 - 10/06/13 04:33 PM

As a control test, have an ICNR session to rule everything else out, other than calibration. Thx

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shawnhar
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Re: I am doing something very very wrong new [Re: Tonk]
      #6121105 - 10/06/13 06:42 PM

Thanks Tonk!

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ICallHimGamblor
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Re: I am doing something very very wrong new [Re: mmalik]
      #6121123 - 10/06/13 06:53 PM

Quote:

As a control test, have an ICNR session to rule everything else out, other than calibration. Thx




I know what some of these words mean.


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Tom and Beth
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Re: I am doing something very very wrong new [Re: ICallHimGamblor]
      #6121128 - 10/06/13 06:56 PM

[quote
(Big SNIP)

hope I'm not embarrassing myself with my noob-ness.






As a relative noob, I doubt very much you are embarrassing yourself. I bet there's a few learning from the replies and help you're getting. I know I am.

Edited by Tom and Beth (10/06/13 06:57 PM)


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akulapanam
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Re: I am doing something very very wrong new [Re: Tom and Beth]
      #6121175 - 10/06/13 07:30 PM

A couple of suggestions:

First don't save your file from DSS instead make a copy of the autosave.tif and then use imagemagick to convert it to 16 bit. My understanding is that DSS has a bug in the 16bit save routine.

Second I think you would be better off without the CLS even if you have to reduce exposure per shot. For me the CLS filter tends to result in a product with bad color cast and requires a large increase in total exposure time.


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akulapanam
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Re: I am doing something very very wrong new [Re: akulapanam]
      #6121200 - 10/06/13 07:49 PM

Also having downloaded your actual file:

As other have mentioned the focus is not great on this image.

The gradient issue looks complex and a lot like the challenges I have faced. I have similar equipment and I wish I had a solution but I don't.

Overall I think you are probably being a little hard on yourself this is a pretty nice picture and looks a lot like some of the photos I have taken. The biggest challenge people who live in a light polluted environment with time constraints have is getting enough exposure time. For me the solution was to go with hyperstar.


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srosenfraz
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Re: I am doing something very very wrong new [Re: ICallHimGamblor]
      #6121218 - 10/06/13 07:59 PM

I think I see the problem. Your "Master Offset" file doesn't look like its taken correctly. A Bias frame (or offset) is a frame that it taken for the least possible time with the camera covered (usually around 1/4000th second). It should be VERY dark - it only contains read noise. Your master offset looks like its a properly exposed image.

What technique and settings are you using for capturing bias frames?


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Tonk
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Re: I am doing something very very wrong new [Re: srosenfraz]
      #6121275 - 10/06/13 08:46 PM

Quote:

First don't save your file from DSS instead make a copy of the autosave.tif and then use imagemagick to convert it to 16 bit. My understanding is that DSS has a bug in the 16bit save routine.




Can you supply a reference to this information? Can you say which specific versions of DSS?

I use DSS and the 16 bit save routine produces no faults for me.


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ICallHimGamblor
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Re: I am doing something very very wrong new [Re: srosenfraz]
      #6121284 - 10/06/13 08:51 PM

Are you sure? I am looking at my bias frames, and they are all dark, and I look at the master offset in DSS and it is dark as dark can be.

As I recall, I took them at 1/2000 shutter speed with the lens cap on in my office, captured using BackyardEOS. I am not sure if somehow somewhere they got mixed up, but they look fine in the directory on my drive.


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Tonk
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Re: I am doing something very very wrong new [Re: Tonk]
      #6121287 - 10/06/13 08:53 PM

Quote:

I think I see the problem. Your "Master Offset" file doesn't look like its taken correctly. A Bias frame (or offset) is a frame that it taken for the least possible time with the camera covered (usually around 1/4000th second). It should be VERY dark - it only contains read noise. Your master offset looks like its a properly exposed image.




Yes that would certainly explain the outcome if the bias is actually not a true bias. As the "bias" data is subtracted from both the dark and light frames and if this is actually a longer exposure - this would kill most of the data!

Quote:

I am not sure if somehow somewhere they got mixed up,




This is an easy mistake to make if you point DSS at the wrong files while loading the bias images


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ICallHimGamblor
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Re: I am doing something very very wrong new [Re: ICallHimGamblor]
      #6121301 - 10/06/13 09:00 PM

Here is a link to a screen shot of my master offset in DSS:

https://drive.google.com/#folders/0By0hG91nGRL9ckxUeXAxUXdTLTQ


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ICallHimGamblor
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Re: I am doing something very very wrong new [Re: ICallHimGamblor]
      #6121315 - 10/06/13 09:06 PM

I am not adverse to the possibility that I have done something really silly here, but here is a link to screenshot the file list I saved in DSS, showing that the biases are listed as biases.

https://drive.google.com/#folders/0By0hG91nGRL9ckxUeXAxUXdTLTQ

EDIT: Actually, I would be willing to bet I've done something stupid... but I don't think that's it

Edited by ICallHimGamblor (10/06/13 09:30 PM)


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srosenfraz
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Re: I am doing something very very wrong new [Re: ICallHimGamblor]
      #6121375 - 10/06/13 09:49 PM

Quote:

Are you sure? I am looking at my bias frames, and they are all dark, and I look at the master offset in DSS and it is dark as dark can be.

As I recall, I took them at 1/2000 shutter speed with the lens cap on in my office, captured using BackyardEOS. I am not sure if somehow somewhere they got mixed up, but they look fine in the directory on my drive.




Your procedure you describe for capturing your bias sounds correct. However, if you look at the file you posted on your Google drive named "MasterOffset_ISO800.tif", its definitely not a dark file.

I'm not sure if somehow you may have posted the wrong file or named it incorrectly, but I think you'll want to figure out why the file you posted as a Master bias is not a dark file. Perhaps its related to the problem, perhaps not. But, if you used the file you posted on Google as a bias frame, it would definitely have ill effects on your stacked image.


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akulapanam
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Re: I am doing something very very wrong new [Re: Tonk]
      #6121377 - 10/06/13 09:52 PM

Quote:

First don't save your file from DSS instead make a copy of the autosave.tif and then use imagemagick to convert it to 16 bit. My understanding is that DSS has a bug in the 16bit save routine.




Reference is below. I have seen a huge improvement using the method suggested to bypass the bug.

http://www.astronomyforum.net/astrophotography-image-processing-forum/154722-...




Edited by akulapanam (10/06/13 09:53 PM)


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srosenfraz
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Re: I am doing something very very wrong new [Re: ICallHimGamblor]
      #6121388 - 10/06/13 10:03 PM

Quote:

Here is a link to a screen shot of my master offset in DSS:

https://drive.google.com/#folders/0By0hG91nGRL9ckxUeXAxUXdTLTQ




Yes, that looks exactly like the image when I debayered your MasterOffset.tif file. The 8 bit RGB values SHOULD be (0,0,0), but the RGB values for your Masteroffset.png file are (96,38,54). I suspect you've been using an invalid bias frame since 6/28/13 (date on your file).

Just for giggles, why don't you try restacking your Stephan's Quintet without using the bias frame. Its not optimal, but I suspect it would be better than what you have. Alternatively, take a minute and try recapturing 30 or so bias frames with the camera and create a new Master Bias. Then restack your Stephan's Quintet.


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ICallHimGamblor
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Re: I am doing something very very wrong new [Re: akulapanam]
      #6121432 - 10/06/13 10:34 PM

Quote:

Quote:

First don't save your file from DSS instead make a copy of the autosave.tif and then use imagemagick to convert it to 16 bit. My understanding is that DSS has a bug in the 16bit save routine.




Reference is below. I have seen a huge improvement using the method suggested to bypass the bug.

http://www.astronomyforum.net/astrophotography-image-processing-forum/154722-...







I couldn't get past the disgusting ad for toenail fungus.


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ICallHimGamblor
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Re: I am doing something very very wrong new [Re: srosenfraz]
      #6121471 - 10/06/13 10:56 PM

I restacked everything with unchecked biases and posted to the folder: https://docs.google.com/file/d/0By0hG91nGRL9SkVmUGJJWW4zQ2s/edit?usp=sharing

My 'other job' is a sports handicapper and involves buying shots and drinking with sports betters, so I no longer have the appropriate blood alcohol level to process it myself but I will give it a shot tomorrow after work, and I will retake my biases if someone can tell me what I did wrong... I thought biases were the easy ones.


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Tonk
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Re: I am doing something very very wrong new [Re: ICallHimGamblor]
      #6121722 - 10/07/13 04:39 AM

Quote:

Reference is below. I have seen a huge improvement using the method suggested to bypass the bug.





Thanks for the link - but it turns out I can't actually see what is said as the site blocks me unless I sell my soul to them. I'm not going to play that game unfortunately

Meantime I suspect the bug may be related to not disabling the application of DSS's stretch function - its an option that is frequently missed by users that don't follow the ins and outs of DSS. This stretch isn't applied to the autosave TIFF - however if you tick the right option boxes is also NOT applied to the 16 bit TIFF save command.

It is well known (to a degree) that DSS's stretch function is far from optimal and degrades the ability to perform further downstream post processing. So the simple solution is to turn it off and not do the long walk around the block

One thing you haven't said - which DSS version was this problem reported and which were you using? I do not use the latest as the newest versions have broken part of the comet stacking (the frames which have been comet marked are no longer displayed with the (C) markers on the user interface - which is a pity)


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Re: I am doing something very very wrong new [Re: Tonk]
      #6122306 - 10/07/13 12:14 PM

Here ya go Tonk, formt he link listed above:
I've received a few requests for this information so I thought I'd post this mini-tutorial.

Things you need to know:

1) Because of a bug in DSS, the "File - Save As" command does not create a high-quality file. It creates a 16-bit tif wrapper with 8-bit data inside it. Eventually this bug should get fixed. Until it does, for the best possible data out of DSS you need to use the Autosave.tif file that it creates automatically after stacking is completed.

2) The Autosave.tif file is itself problematic. It contains 16-bits of real data + 16-bits of zeroes within a 32-bit tif wrapper (quite why it does this is unclear).

3) Some editing/AP packages can handle this format without any problems... PixInsight for example. Photoshop can also handle it UP TO A POINT although presumably it will think that the 32-bit data indicates an HDR (High Dynamic Range) image file that it can open for display purposes but do nothing else with until it is converted to 16-bit data (within Photoshop itself).

4) Some editing/AP packages will not open the Autosave.tif file at all.

5) Unless you use an Editing/AP package that can handle the 32-bit Autosave.tif file your best course of action is to convert the file to a true 16-bit tif file. A convenient tool for doing this conversion with no quality loss is ImageMagick


Using ImageMagick

I am no expert in IM. I only use it for this one specific task (in fact, to be honest I don't use it at all because I use PixInsight... but it is a handy tool to have around).

To install IM, go to the ImageMagick site and follow the download and install instructions. There are separate versions for Win32 and Win64 - make sure you get the correct one - see first attachment. Also get the "static" versions (ignore the other versions).

IM is a powerful suite of tools of which we are going to use precisely one; the "Convert" tool.

IM runs from the Windows command line - no fancy GUI here!

To use IM, do the following:

1) open a Windows Command session (type "CMD" into the "search programs and files" box on the Start Menu)
navigate to the Drive/folder containing your autosave.tif file using trusty old DOS commands (I'm going to assume you know how to do this...)

2) type: convert autosave.tif -depth 16 yournewfilename.tif (then hit "enter")

3) wait a few seconds (you may get some warning messages - you can completely ignore them... they are caused by the way that DSS creates the autosave.tif file)

4) a DIR command will show you the new file which will be ~half the size of the original, as you would expect

See second attachment.

That's it. Done. Enjoy
Phil


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Pete GLA
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Re: I am doing something very very wrong new [Re: ICallHimGamblor]
      #6123168 - 10/07/13 05:31 PM

Quote:






Can someone do an autopsy on this image to figure out what I am doing wrong?

Thanks.




I am not a regular imager, but being in a red-white zone myself, and if trying the Quintet (or any other DSO), i'd get the same result.

Your 3 minutes @ ISO 400 closely matches my settings...

A typical session allows me to do 3'.5 @ ISO 400, 2'.5 @ 640 and around 2' @ 800.

Going 5' @ ISO 800... well the peak on the histogram is going be at least 66%...

What you could try is image opposite light domes...I have Downtown Detroit 2 miles west of me, so I don't do any imaging to the west.

You're doing nothing wrong...just wrong place!!!

This is my experience.

Pete

OOPS...Didn't read all of the responses...

Edited by Pete GLA (10/07/13 06:00 PM)


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Tonk
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Re: I am doing something very very wrong new [Re: shawnhar]
      #6123237 - 10/07/13 05:52 PM

Quote:

The Autosave.tif file is itself problematic. It contains 16-bits of real data + 16-bits of zeroes within a 32-bit tif wrapper (quite why it does this is unclear).




Quote:

Some editing/AP packages will not open the Autosave.tif file at all.




Why this is so is easy - its a private TIFF format that DSS uses to cache intermediate data during stacking and for reloading once the stacking is done - its not designed for users to play with. Hence many programs can't deal with it.

Quote:

Because of a bug in DSS, the "File - Save As" command does not create a high-quality file. It creates a 16-bit tif wrapper with 8-bit data inside it.




I find this troubling as this is not my experience at all. At least the evidence when opening a 16 bit in Images plus is contrary to this - e.g. the histogram data statistics do not concur and there are no gaps (combing) which is what you would expect with an 8 bit depth file maskerading as a 16 bit file.

If this is really the case then posterization of brightness data after even a basic stretch would be very evident (like it is in GIMP which is still stuck at 8 bits). I don't see this after any sort of stretching in Images Plus ... so it is now greatly puzzling me why we are just hearing of this.

Which makes me think that if there is a bug it may be down to specific types of RAW file input (i.e. from a particular camera model) The only thing I can think might be an issue is if some has been using a newer model camera and hasn't picked up the DSS beta with the newest DCRaw program - i.e. the problem actually lies with using an too old version of the DCraw program that DSS uses.

It would be interesting if more information was available - camera used etc


I've just done an intensive Google on this issue and I can find nothing else reported or said by anyone. The nearest is Sander Pool (DSS Yahoo Groups guru) mentioning that post processing in GIMP is limited by it 8 bit depth. I would have though if anyone was going to make a song+dance of this bug Sander would!



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ICallHimGamblor
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Re: I am doing something very very wrong new [Re: Tonk]
      #6123610 - 10/07/13 09:05 PM

I created a new set of biases and restacked it.

Here is the new master offset: https://docs.google.com/file/d/0By0hG91nGRL9VDBuamdHN3dGMXc/edit?usp=sharing

And the new stack: https://docs.google.com/file/d/0By0hG91nGRL9QzJaOWpBQlJ6X2s/edit?usp=sharing

It looks better to me, but I really am not sure.

Did this solve the calibration issue?


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Re: I am doing something very very wrong new [Re: ICallHimGamblor]
      #6123633 - 10/07/13 09:18 PM

I'm no expert, but I'd try just stacking the lights and see how it looks. That is, no calibration. That would tell you if the calibration frames are a problem.

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akulapanam
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Re: I am doing something very very wrong new [Re: Tonk]
      #6123762 - 10/07/13 10:53 PM

Quote:

Quote:

The Autosave.tif file is itself problematic. It contains 16-bits of real data + 16-bits of zeroes within a 32-bit tif wrapper (quite why it does this is unclear).




Quote:

Some editing/AP packages will not open the Autosave.tif file at all.




Why this is so is easy - its a private TIFF format that DSS uses to cache intermediate data during stacking and for reloading once the stacking is done - its not designed for users to play with. Hence many programs can't deal with it.

Quote:

Because of a bug in DSS, the "File - Save As" command does not create a high-quality file. It creates a 16-bit tif wrapper with 8-bit data inside it.




I find this troubling as this is not my experience at all. At least the evidence when opening a 16 bit in Images plus is contrary to this - e.g. the histogram data statistics do not concur and there are no gaps (combing) which is what you would expect with an 8 bit depth file maskerading as a 16 bit file.

If this is really the case then posterization of brightness data after even a basic stretch would be very evident (like it is in GIMP which is still stuck at 8 bits). I don't see this after any sort of stretching in Images Plus ... so it is now greatly puzzling me why we are just hearing of this.

Which makes me think that if there is a bug it may be down to specific types of RAW file input (i.e. from a particular camera model) The only thing I can think might be an issue is if some has been using a newer model camera and hasn't picked up the DSS beta with the newest DCRaw program - i.e. the problem actually lies with using an too old version of the DCraw program that DSS uses.

It would be interesting if more information was available - camera used etc


I've just done an intensive Google on this issue and I can find nothing else reported or said by anyone. The nearest is Sander Pool (DSS Yahoo Groups guru) mentioning that post processing in GIMP is limited by it 8 bit depth. I would have though if anyone was going to make a song+dance of this bug Sander would!






There are several threads on astronomyforum that detail the issue with photos. I'm sure that their is at least one in DSS on yahoo because I believe I posted in the thread. When I get a sec I'll post links for you but you will have to register.


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Tonk
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Re: I am doing something very very wrong new [Re: akulapanam]
      #6124109 - 10/08/13 04:05 AM

Quote:

Eventually this bug should get fixed. Until it does, for the best possible data out of DSS you need to use the Autosave.tif file that it creates automatically after stacking is completed.




So has Luc acknowledged this bug and given a indication of when it will be fixed? Do you have a link to the bug report?


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Re: I am doing something very very wrong new [Re: Tonk]
      #6124981 - 10/08/13 01:45 PM

I'm with Tonk, I think this is mis-informed info, someone is confused about 8bit vs 16bit. I tried the "fix" of converting the autosave from DSS to a 16bit tiff and saw no difference whatsoever at 100% zoom between that and the regular output tiff.
8 bit sucks, even when in a 16 bit wrapper, you will know 8 bit instantly when you stretch because it looks like Nintendo, the 1st one.


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Tonk
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Re: I am doing something very very wrong new [Re: shawnhar]
      #6126465 - 10/09/13 07:42 AM

Quote:

I think this is mis-informed info, someone is confused about 8bit vs 16bit.




+1. The so called bug is bogus. Just done my own checks via the data "fix" - like you no difference found.


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ICallHimGamblor
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Re: I am doing something very very wrong new [Re: Tonk]
      #6126525 - 10/09/13 08:36 AM

So did my new biases fix my calibration issue? It looks better when I auto-dev in StarTools, but I still can't get much data out of it.

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shawnhar
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Re: I am doing something very very wrong new [Re: ICallHimGamblor]
      #6126898 - 10/09/13 12:29 PM

I tried it and it has the same gradients...

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ICallHimGamblor
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Re: I am doing something very very wrong new [Re: shawnhar]
      #6126957 - 10/09/13 01:04 PM

In that case, I am kinda stuck. I don't know what to try next. Any suggestions would be greatly appreciated.

Can I go longer on subs? Should I bump ISO to 800? How important is the pointer that I read that the histogram of the subs should be about 1/3 of the spectrum?


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pfile
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Re: I am doing something very very wrong new [Re: ICallHimGamblor]
      #6127073 - 10/09/13 01:59 PM

the gradients in this image are completely wild... are you sure that the subs were not taken thru clouds or that some of the subs have trees or a house or something in them?

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shawnhar
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Re: I am doing something very very wrong new [Re: pfile]
      #6127235 - 10/09/13 03:13 PM Attachment (2 downloads)

1st, stack without the flats, I would start there, have taken more than my share of bad flats, they are easy to get wrong.
2nd, I have taken pics where the histo was over half and ones where it was on the left wall. The ones one the left wall will be noisy as all get out, the ones over half will have a horrible washed out look that can be difficult to deal with, but it's better than being jammed up against the wall or limited to 2 minute subs. I have also dropped to iso 400 to get 10 minute subs and they came out fine.
Try iso 400 and go as long as you can without going over halfway on the histo and you will be fine.
Those gradients on the other hand...you gotta figure out what is causing that. Start with the flats, if that ain't it, maybe what is in your area that is casting light on your lens? My money is now on the flats.
Other than the gradient I think you are getting good data.


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srosenfraz
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Re: I am doing something very very wrong new [Re: shawnhar]
      #6127591 - 10/09/13 06:19 PM

The new bias frame you posted still doesn't look right. Its level is at 56, where it should be at 0. Now, its possible that the bias is ok, and what you're posting has had some stretch applied, but there's something not right about the Master offset file you posted. That may or may not be the issue, but I think you'll want to resolve the discrepancy.

@Shawn - since you're familiar with DSS, would you mind giving ICallHimGamblor directions on how to save an unstretched Master offset tiff file?

@ICallHimGamblor - Would it be possible to post a raw sub (the .cr2 file itself)? That will give us a much better idea as to what your raw data looks like before anything is done to it.


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Re: I am doing something very very wrong new [Re: srosenfraz]
      #6127737 - 10/09/13 07:43 PM

I've been having a lot of issues with DSS as well. It looks to be reversing my flats at times, hollow stars, ect. I have found a few settings that seem to help get consistent results.

Under registration
Check automatic detection of hot pixels
Under advanced, reduce noise using median filter
Then adjust the slider and do multiple test runs until you end up with a number of stars that looks like what is in your image.

In the stacking tab use "Standard" under Result
Do a Median combine for lights, darks, flats, bias
Under alignment choose Bilinear
Under cosmetic, uncheck everything

For the best stretch, I save it out as 32bit rational then do a linear stretch before converting it to 16bit.

Seems to make it work right for me for some reason.

Cheers,


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ICallHimGamblor
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Re: I am doing something very very wrong new [Re: Rankinstudio]
      #6127972 - 10/09/13 10:02 PM

Thanks, everyone... everyone is being so helpful.

Scott: I uploaded a single random sub here: https://docs.google.com/file/d/0By0hG91nGRL9WkZoUFFwRWQ3SEE/edit?usp=sharing

David: Thanks.. I will try restacking and re-saving tomorrow when I have a little more time.

Right now, I'm going to try stacking in my Nebulosity trial to see if it makes a difference.


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shawnhar
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Re: I am doing something very very wrong new [Re: srosenfraz]
      #6128534 - 10/10/13 08:43 AM Attachment (3 downloads)

Quote:


@Shawn - since you're familiar with DSS, would you mind giving ICallHimGamblor directions on how to save an unstretched Master offset tiff file?




In the folder where your flats are, DSS will generate a master flat when you stack them, same with the darks and bias, but that ain't the problem.
Your single sub has those crazy gradients as well.
What is the light like around you? Streetlight behind some leaves shining in the scope? Gotta figure this out 1st...


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ICallHimGamblor
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Re: I am doing something very very wrong new [Re: shawnhar]
      #6129860 - 10/10/13 08:57 PM

I am in the city, and there are definitely streetlights around, though none with any direct light. There is one nearby behind some leaves.

However, due to trees I am shooting mostly straight up. I bet I started my imaging of this set at 85 degrees above the horizon.

Am I basically just screwed completely because I live in the city? I am pretty sure there are folks on this forum getting decent results in metropolitan areas.


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pfile
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Re: I am doing something very very wrong new [Re: ICallHimGamblor]
      #6129962 - 10/10/13 09:46 PM

you may need a light pollution filter, in which case you should be able to get images of emission nebulae at the very least. i have taken these images with a modified DSLR + lenses and telescopes as well, in what is a red zone according to the maps:








i used the Astronomik CLS filter. it is pretty unkind to galaxies, because it "deletes" a lot of wavelengths that galaxies emit. so with CLS it's easier to stick with Ha/OIII rich targets.

it can be done, don't give up

anyway, those gradients look like clouds or even dew on your scope/lens; i don't think i've ever seen such a complex gradient in any of my subs. usually the gradient is mostly linear in nature.

rob

Edited by pfile (10/10/13 09:49 PM)


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ICallHimGamblor
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Re: I am doing something very very wrong new [Re: pfile]
      #6129987 - 10/10/13 10:01 PM

I have uploaded a random sub from a week earlier on a completely different target, Hickson 93.

https://docs.google.com/file/d/0By0hG91nGRL9clVEX25QUFFCakk/edit?usp=sharing

Does it have the same issues? If so, we can eliminate clouds and dew and stuff, right?


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srosenfraz
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Re: I am doing something very very wrong new [Re: ICallHimGamblor]
      #6130039 - 10/10/13 10:22 PM

Suggestion - you're trying to image some very challenging targets from very light polluted skies. While its possible to do, it might serve you better to start with some brighter targets and refine your routines and techniques for image capture and processing. Targets like Stephan's Quintet and Hickson 93 can make for some beautiful and impressive images. But, they also demand tight focus to capture the small details plus a lot of exposure to give a good SNR due to their relatively low surface brightness. When you're imaging from light polluted skies, you'll typically need to increase that total exposure time to many, many times what it takes at a dark sky (i.e., a target I can capture well in 1 hour from my blue/green zone sky will take 8 hours for comparable SNR in a red zone). As such, if you try working more with objects with a higher surface brightness, you can capture them in a more reasonable amount of time and start seeing some positive results.

You're not completely screwed because you're in the city, but it does make things more difficult. Still, there's a long list of bright targets (high surface brightness) that should be comparatively easy for you to capture (Mr. Messier developed a pretty good list for starters).

Hope this helps...


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ICallHimGamblor
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Re: I am doing something very very wrong new [Re: srosenfraz]
      #6130082 - 10/10/13 10:43 PM

Scott: I completely understand what you are saying, and I agree. I just have very little interest in those targets. I don't mind at all spending 8 hours on a neat Hickson group, as long as I know something useful will come out of it.

I do have some subs of the Deer Lick Group and NGC 6946 that are equally as disappointing in my opinion, and those are pretty bright, large galaxies. In fact, NGC 6946 came out worst of them all.

If the answer to all my problems is just "you need more exposure time", then that's fine. I'm good with that. But it sounds like I'm doing something wrong if my bias frames don't come out black and I'm getting psychotic gradients on three minute subs.

But while I'm learning, I will also seek out some easier targets. Your advice is definitely taken.


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pfile
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Re: I am doing something very very wrong new [Re: ICallHimGamblor]
      #6130242 - 10/11/13 12:26 AM

so just as a sanity check, did you stack without any calibration frames and check the results?

it is hard to see the gradients in a single sub. what i can see though is that the vignetting in each channel is very different, which is a little strange for a reflecting telescope. still there are refracting elements in an SCT which might account for that.

also your camera temperature is way up there at 97F (36C). this can really make it difficult to collect dim targets. you may want to investigate building a cooler box to keep the thermal signal down.

rob


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Re: I am doing something very very wrong new [Re: ICallHimGamblor]
      #6130486 - 10/11/13 07:29 AM Attachment (1 downloads)

Quote:

I have uploaded a random sub from a week earlier on a completely different target, Hickson 93.

https://docs.google.com/file/d/0By0hG91nGRL9clVEX25QUFFCakk/edit?usp=sharing

Does it have the same issues? If so, we can eliminate clouds and dew and stuff, right?



Seems to have the same gradient.
Take a raw with the lens, pointed at a surface that is uniformly colored, like a wall and see if it still has it.


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Tonk
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Re: I am doing something very very wrong new [Re: shawnhar]
      #6130554 - 10/11/13 08:39 AM

That look like plain old vignetting as far as the brightness drop off to the corners is concerned (that's sorted by flats) - the dark band along the bottom is often due to the spongy strip padding that runs on one edge to damp out the mirror slap - that too is cured by flats

- or are you referring to the weak coloured gradients on top. No idea what doing that and flats would not likely solve those


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ICallHimGamblor
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Re: I am doing something very very wrong new [Re: Tonk]
      #6130730 - 10/11/13 10:27 AM

Oh man.. I really hope we are back to just having a problem with my flats.

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shawnhar
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Re: I am doing something very very wrong new [Re: ICallHimGamblor]
      #6130832 - 10/11/13 11:21 AM

It's the color gradient that is causing the issue. I am not really sure what is causing it or how to deal with it, never seen gradient like that on one sub except shooting through clouds. The gradient appears to be the same on each non-calibrated exposure, suggesting it is internal to the camera or the scope.

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ICallHimGamblor
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Re: I am doing something very very wrong new [Re: shawnhar]
      #6130950 - 10/11/13 12:09 PM

Is there a camera setting that could affect this? That might also explain why my biases are not black.

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srosenfraz
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Re: I am doing something very very wrong new [Re: ICallHimGamblor]
      #6131234 - 10/11/13 02:12 PM

I have a feeling your bias problem is in how your processing/posting it in DSS. Could you post one .CR2 RAW of a bias frame? That will help us ensure that your bias data is good and its the processing/posting of the bias is why we're not seeing a black master bias

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ICallHimGamblor
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Re: I am doing something very very wrong new [Re: srosenfraz]
      #6131405 - 10/11/13 03:31 PM

One raw bias frame coming up: https://docs.google.com/file/d/0By0hG91nGRL9REQzNHpBNnFtVFk/edit?usp=sharing

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srosenfraz
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Re: I am doing something very very wrong new [Re: ICallHimGamblor]
      #6131527 - 10/11/13 04:30 PM

Ok, so the good news is that your bias raw looks like a nice, normal 0,0,0 all over the place bias frame. My gut suspicion is that when you're saving the .tif out of DSS, your applying a stretch to it and that's why it doesn't look normal. I would assume for the time being that DSS is actually applying it as a very dark bias frame when its using it to calibrate the flat.

Again, perhaps someone familiar with DSS can explain why his normal looking bias ends up in a Master Offset .tif that is clearly not dark?

For the time being, let's assume your bias is OK (sorry if I had led us astray). As I look through this thread, I noticed that I and others have been referring to your filter as a CLS filter. My assumption was just that - that it was the Astronomik CLS-CCD filter. However, I notice that you keep referring to it as an LP filter. So, clearly its a filter other than the CLS-CCD filter.

Which begs the question - exactly what LP filter are you using? Specifically, brand and model?


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shawnhar
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Re: I am doing something very very wrong new [Re: srosenfraz]
      #6131563 - 10/11/13 04:53 PM

I think Scott is on to something.
You need to take it back to the lowest common denom.
Start with the camera, no filter, and a lens. Take a RAW pic of something uniform in color like a blue wall. Gradient?
Add the filter, take same pic
See the gradient yet?
If not add the scope, indoors, aim at wall, take pic, see the gradient yet? etc...etc...


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ICallHimGamblor
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Re: I am doing something very very wrong new [Re: shawnhar]
      #6131599 - 10/11/13 05:10 PM

Unfortunately, I have absolutely no Canon lenses. I bought the camera body from Canon Direct knowing I would not be using it for any other purpose.

Scott: The LP filter I bought is the Orion SkyGlow imaging filter. There was another thread on here somewhere where that was what I was told to buy.


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shawnhar
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Re: I am doing something very very wrong new [Re: ICallHimGamblor]
      #6131604 - 10/11/13 05:14 PM

Just uncap the camera and take a pic of a wall using AV

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proteus5
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Re: I am doing something very very wrong new [Re: shawnhar]
      #6132252 - 10/11/13 11:47 PM

ICallHimGamblor,

As for the gradient, are you covering the viewfinder on the back of the camera when you take your long exposure subs? There should be a black rubber rectangle on the neck strap that came with your camera. You'll need to remove the eyeguard from the viewfinder, and then put on the rubber cover. This blocks any stray light that might enter the camera through the viewfinder during long exposures. I had this problem when I first started as I also image from a red zone with numberous lights around. I'd get some crazy gradients in the middle of some images as the scope rotated through the night. I now cover the viewfinder and no more strange gradients. Oh and use the cover for your darks, flats, and bias frames also. Hope that this helps.


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shawnhar
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Re: I am doing something very very wrong new [Re: proteus5]
      #6132712 - 10/12/13 10:10 AM

I really hope that is the issue.
Sweet tip about the cover being on the neck strap, did not know that.


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ICallHimGamblor
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Re: I am doing something very very wrong new [Re: shawnhar]
      #6132837 - 10/12/13 11:20 AM

That's a great idea, Robert. I have not covered the viewfinder ever, but I found the cover on the strap like you said and it is installed now. Can't wait to try it out.



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srosenfraz
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Re: I am doing something very very wrong new [Re: ICallHimGamblor]
      #6133302 - 10/12/13 03:42 PM

I think Robert may have hit the nail on the head - what you're seeing is quite consistent with a light leak where you have a fair amount of local LP (oddball gradients, very low contrast subs). Let us know what happens when you try your next capture....

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proteus5
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Re: I am doing something very very wrong new [Re: srosenfraz]
      #6133636 - 10/12/13 07:02 PM

Hope it's an easy fix for you. My gradients weren't bad until I started 5 minute or more exposures, and the cover helped a lot. Here's hoping that's the trouble. Let us know.

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ICallHimGamblor
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Re: I am doing something very very wrong new [Re: proteus5]
      #6135337 - 10/13/13 04:21 PM

It looks like based on weather and moon and work commitments that it will be at least ten days before I can image again, but I wanted to thank everyone one last time for helping me debug this issue.

I don't see a 'buy you all a beer' smiley, so you get this little guy:


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proteus5
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Re: I am doing something very very wrong new [Re: ICallHimGamblor]
      #6137401 - 10/14/13 04:28 PM

You're welcome, and be sure to let us know how you make out.

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