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Show Time! (for you if you don't mind)


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Hello again!

Your time to shine:)! Not mine...

I managed to take some first pictures using the sig setup and it pretty much worked a treat having put it all together for the first time. I need to get my head around a few things before I go out to a dark site, so these pictures were taken from a balcony in the middle of a major city...

So I took 30 subs - 2 minutes guided at ISO400 and some 20 darks. M57 seemed a nice enough target.

(Sure LP is a huge huge issue here but I wanted some data to play around with a try and learn)

Next step to let DSS have a crack. I noticed that the Canon RAW files appeared in DSS with the wrong resolution (way off) and in greyscale, so I let the Canon software convert to TIFF and tried again in DSS.

It worked a treat this time and it produced a greyish image as per usual. Then I got confused again...

Comparing a single sub with the stacked image was like looking at before and after in reverse!

I know nothing about editing but I have gathered that histograms need stretching and when I give that a go the stacked image behaves like a measly jpeg and the strangest things happen - visually unpleasant:rolleyes:. I tinkered a bit with a lone sub and even I can improve it to some extent...

So Show Time! Any chance you could have look at the images below and give me some hints what might be at fault?

I know it's a steep learning curve but this is an overhang pitch!

Thanks for your time!

/Jessun

Below is a crop of one sub, a play around attempt with this, and finally a crop of the stack.

M57 SINGLE SUB CROP FOR SGL.tif

M57 SINGLE EDIT CROP.tif

M57 For SGL.tif

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What exactly do think it means when you say, "histograms need stretching. . . " A histogram should show a hump in the middle of the graph between the blackest black and the whitest white. This does NOT mean that you should take the sliders and move them up to each side of where the hump is.

It appears to me that you have reduced the range of luminance levels of your stack to almost completely white! Are you doing all of your post stacking work with DSS ? You might want to consider using different image processing software to adjust the dynamic range of your resulting stack.

I'm sure someone else will jump into lend better advice, but I would appreciate your input on what you think "stretching the histogram. . . " means to you.

Thanks. Good luck, Jim S.

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Hi JimStan!

Thank you for having a look at my post. I know I'm in at the deep end starting from scratch with astrophotography and editing:)

I am totally new on editing/processing and I am spending hours on end online for tutorials etc. Two I came across were these:

How to stretch the histogram using levels and curves

and

so I believe you are right in saying that I've been moving the sliders towards what starts out as "spikes" to make them more like lumps. That is my initial understanding of the tutorials above.

I have problems with the RAW (CR2) files that my Canon 600D produces. In DSS they come out very dark and out of proportion when stacked. Resolution is read by DSS as 1336*3516 grayscale...

Picture one below is a DSS screen shot of the above problem.

Picture two is same stack result (now converted to TIFF stacked with recommended settings and not tinkered with one bit.)

Picture three is what Nebulosity will align and combine using the same TIFFs.

Picture four shows a Screen shot from Nebulosity.

Picture five shows the above Nebulosity result edited somewhat with the "Powerstrech" tool.

(Nebulosity reads the CR2 as greyscale but with the correct resolution by the way...)

I feel ever so slightly more comfortable with Nebulosity than DSS at the moment, but I am struggling with even basic editing still. Mind you my pictures are nothing much to edit but serve as learning.

Thanks again for your answer!:p

/Jessun

PS I would love to have someones unedited stack of something a bit more grand than my measly M57 - just so I can learn more about editing.

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post-28991-133877667592_thumb.jpg

post-28991-133877667594_thumb.jpg

post-28991-133877667599_thumb.jpg

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Jessun, what you are describing about DSS makes me think that the 600d raws are not recognised by DSS properly as yet. Therefore, if that's the case, you can't use it reliably. If I've read the information from the dcraw page properly, dcraw supports the 600d, but not in the version that is bundled with DSS. It looks like the DSS version with 600d support is currently in beta. Try converting the raw files to tif's and loading those instead.

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Thank you John!

Not always good to have the latest gear... I have only managed to convert the RAWs in Canon's program, I tried IrfanView and they come out black...

But with TIFFs in DSS, looking at the second screenshot above, is that what you would expect it to churn out after stacking? (Yes that whitish field above the graph is actually the result stacked picture!!)

Thanks again for your answer

/Jessun

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I found that almost all my "Autosave.tif" files when previewed in DSS (just before I close the program and fire up PS) are completely white.

One I get them in PS, they look fine though, and I process them as normal.

So before you write the stacked tif file off - open it in another program and check it first.

Cheers

Ant

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Thanks for all input!

I'll check out dcraw too.

Does PS open the Autosave.tif as it is? I don't have PS and no program I've got can open it. My autosaves come up with a black band at the edge (See attachment)

I have spent more time in DSS today (well, the whole day), and I think I'm making small steps forwards. From a folder I was about to delete because it was rubbish, all of a sudden I managed to fish out M101. Ok still rubbish by any standards but it's a small scope looking out from a wobbly building in the middle of a city. See second picture.

All in all I now think I can chuck all my stuff in the car and drive a couple of hours away from town to try at a dark site for the first time.

Last night I also tried a skyglow filter, but found my ISO had to be ramped up to 800 from 400 without... The subs turned pink instead and I noticed no benefit at all...

I hope to get out tonight!

/Jessun

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post-28991-133877667629_thumb.jpg

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