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Newbie at DSO - Why is DSS making my different shading levels appear as contours?

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#1 rj144

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Posted 30 November 2020 - 06:32 PM

So I just got a telescope a few weeks ago and just started to try to do DSO.  I'm just practicing now.  My telescope is a Celestron C6se on an Alt-Az mount, so not great for photography.  But the other day I managed to track Orion pretty well taking 2 second subs, and manually adjusting the tracking every 15 minutes or so.  I did this for 1.5 hours and stacked the pics using DSS and edited a bit in Photoshop.  Again, I'm just practicing, so I don't expect miracles, but this is the result:

 

 p4NBkdj.jpg

 

Now the colors are all off, but I'll work on that later.  Why do the different shades appear so much like a contour (the demarcations between shades is not smooth)?  Is it something in DSS that someone has seen before?  I Googled online but couldn't find anything.

 

Thanks.



#2 Jerry Lodriguss

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Posted 30 November 2020 - 06:49 PM

This is not DSS.

 

Be sure to save a 16-bit image out of DSS and do not apply the DSS adjustments.

 

It looks like extreme processing to low-bit data.

 

More info on using DSS here.

 

Basic image processing in Photoshop for deepsky images here.

 

You resolved the Trapezium, that is excellent.

 

Jerry


Edited by Jerry Lodriguss, 30 November 2020 - 06:50 PM.

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#3 rj144

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Posted 30 November 2020 - 06:49 PM

Here's another pic I took just with a camera with a 300 mm lens on a tripod... manually adjusting the tripod every few minutes.  If you zoom in, you see the same contours:

 

5Z3z3rL.jpg



#4 Scott Mitchell

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Posted 30 November 2020 - 06:52 PM

What format are you saving your images in? The ones you are feeding into DSS?


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#5 rj144

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Posted 30 November 2020 - 06:54 PM

This is not DSS.

 

Be sure to save a 16-bit image out of DSS and do not apply the DSS adjustments.

 

It looks like extreme processing to low-bit data.

 

More info on using DSS here.

 

Basic image processing in Photoshop for deepsky images here.

 

You resolved the Trapezium, that is excellent.

 

Jerry

Thanks so much for your reply.  But it is saved as 16 bit with no adjustments.

 

I get that it looks like low bit data, but why is it so uniform on each contour?  It looks like a processing artifact not S/N artifact as I would think I would see more randomness in each contour. Even in the lightest part of the image at the center, there are contours.



#6 rj144

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Posted 30 November 2020 - 06:55 PM

What format are you saving your images in? The ones you are feeding into DSS?


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Thanks.

 

Yes, I should have mentioned Sony ARW on the first post and Nikon NEF files on the 300 mm shot in the second post.



#7 Scott Mitchell

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Posted 30 November 2020 - 06:59 PM

I assume those are the raw image formats for those cameras? If so then that's all good. Not sure what's going on then.


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#8 rj144

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Posted 30 November 2020 - 06:59 PM

This is a very zoomed in portion of the second image:

 

Ece9I0Q.jpg

 

It's a little hard to see, but it's there too.



#9 rj144

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Posted 30 November 2020 - 07:01 PM

I assume those are the raw image formats for those cameras? If so then that's all good. Not sure what's going on then.


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Thanks.   They are.


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#10 jonnybravo0311

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Posted 30 November 2020 - 08:09 PM

Can you upload a completely unedited raw light frame you took to a google drive or dropbox or similar? (one from each setup - the scope and the camera on tripod). 2s subs for 90 minutes... that would be 2700 subs.

 

Not sure how many subs you took with the camera on the tripod... or what camera or lens or what tripod you're using. I'm not sure what you're doing in DSS... if you're trying to process it or you're somehow setting something wonky, because my results doing a very similar experiment turned out quite differently:

 

Wide Angle View of Orion Nebulae

 

That was stacked in DSS and processed in PixInsight. It's 1200 light frames at 2s each using my G9, 50-200mm lens at 100mm, f/4, ISO 3200.

 

This is how a single sub looks from that data (converted to JPG):

 

M42 Single 2s Sub

Edited by jonnybravo0311, 30 November 2020 - 08:10 PM.

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#11 rj144

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Posted 30 November 2020 - 09:37 PM

Can you upload a completely unedited raw light frame you took to a google drive or dropbox or similar? (one from each setup - the scope and the camera on tripod). 2s subs for 90 minutes... that would be 2700 subs.

 

Not sure how many subs you took with the camera on the tripod... or what camera or lens or what tripod you're using. I'm not sure what you're doing in DSS... if you're trying to process it or you're somehow setting something wonky, because my results doing a very similar experiment turned out quite differently:

 

 

 

That was stacked in DSS and processed in PixInsight. It's 1200 light frames at 2s each using my G9, 50-200mm lens at 100mm, f/4, ISO 3200.

 

This is how a single sub looks from that data (converted to JPG):

 

Thanks... I'll do that in a bit.  But that looks very nice.

 

It was a Nikon 70-300 mm VR ED at 300 mm, at I believe, ISO 1000.  The subs were 0.8 s and there was about 1400 of them.



#12 rj144

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Posted 30 November 2020 - 09:41 PM

Can you upload a completely unedited raw light frame you took to a google drive or dropbox or similar? (one from each setup - the scope and the camera on tripod). 2s subs for 90 minutes... that would be 2700 subs.

 

Not sure how many subs you took with the camera on the tripod... or what camera or lens or what tripod you're using. I'm not sure what you're doing in DSS... if you're trying to process it or you're somehow setting something wonky, because my results doing a very similar experiment turned out quite differently:

 

 

 

That was stacked in DSS and processed in PixInsight. It's 1200 light frames at 2s each using my G9, 50-200mm lens at 100mm, f/4, ISO 3200.

 

This is how a single sub looks from that data (converted to JPG):

 

Here is the NIkon NEF for the second shot on the tripod:

 

https://app.box.com/...s4yqi3yd3yduy27

 

Here is Sony ARW for the first shot on the telescope:

 

https://app.box.com/...1dduyzlkaci6tas



#13 jonnybravo0311

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Posted 30 November 2020 - 10:40 PM

Here is the NIkon NEF for the second shot on the tripod:

 

https://app.box.com/...s4yqi3yd3yduy27

 

Here is Sony ARW for the first shot on the telescope:

 

https://app.box.com/...1dduyzlkaci6tas

Thanks. I just grabbed these and opened them both in PixInsight. I don't see any of the issues you're showing. Here's the screenshot:

 

PI M42 rj144

 

So, there's nothing wrong with the subs. What does the stacked image out of DSS look like? Again, no edits, just the linear, unstretched 16 bit autosave.tif that gets generated. Also, if you can lay out the steps/options you picked in DSS to do the stack that would be helpful.



#14 rj144

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Posted 30 November 2020 - 11:22 PM

Thanks. I just grabbed these and opened them both in PixInsight. I don't see any of the issues you're showing. Here's the screenshot:

 

 

 

So, there's nothing wrong with the subs. What does the stacked image out of DSS look like? Again, no edits, just the linear, unstretched 16 bit autosave.tif that gets generated. Also, if you can lay out the steps/options you picked in DSS to do the stack that would be helpful.

Thanks.  Yeah, I didn't see anything weird in the individual images which I thought it was something related to the stacking process.

 

Here is the first TIF with the scope:

 

https://app.box.com/...kf7dwk64zmg769b

 

This is the second TIF on the tripod:

 

https://app.box.com/...hn1l3xxkgtqsjfl

 

I just used default settings for both on DSS with 40 darks and 20 dark bias frames, but no flats for each, just to see how that works.



#15 jonnybravo0311

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Posted 01 December 2020 - 12:12 AM

Those stacked files are too small. They should be far larger. 15.6MB and 145.9MB for the final stacked results? For example, the image I shared above of Orion the stacked result is 244MB.

 

Your "300mm" file is closer to the appropriate size, but there's definitely something still wrong with it. It's like you saved your resulting stacked image in 4 bit How many subs did you stack for the camera/tripod result? How about for the telescope result?

 

More curious details... the raw file from your Sony camera is 3936x2624, but your stacked image is 1968x1324 - just about half the size.

 

So, the resulting stacked image is too small by far (both in pixels and storage) and even though it claims to be 16 bit depth, the render is showing like it's something from back in the early '80s on a CYMK 4 color monitor :p

 

I really suggest you take a look at the settings in DSS. Make sure you're not doing something like creating super-pixels in the RAW development process settings (choose bilinear interpolation). You'll have to restack.


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#16 rj144

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Posted 01 December 2020 - 01:16 AM

Those stacked files are too small. They should be far larger. 15.6MB and 145.9MB for the final stacked results? For example, the image I shared above of Orion the stacked result is 244MB.

 

Your "300mm" file is closer to the appropriate size, but there's definitely something still wrong with it. It's like you saved your resulting stacked image in 4 bit How many subs did you stack for the camera/tripod result? How about for the telescope result?

 

More curious details... the raw file from your Sony camera is 3936x2624, but your stacked image is 1968x1324 - just about half the size.

 

So, the resulting stacked image is too small by far (both in pixels and storage) and even though it claims to be 16 bit depth, the render is showing like it's something from back in the early '80s on a CYMK 4 color monitor tongue2.gif

 

I really suggest you take a look at the settings in DSS. Make sure you're not doing something like creating super-pixels in the RAW development process settings (choose bilinear interpolation). You'll have to restack.

 

Thanks... super helpful.

 

Now that I remember, I did think I checked super pixel because almost no stars were detected even after adjusting the threshold way down because the stars are not points for the telescope pic. I'll see if I did that.

 

For the pic on tripod, I definitely did not do that.  For the tripod pic it was 1400 subs, for the telescope something like 2800.

 

I'll try to restack again though.

 

Thanks.




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