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FaB-Bo-Peep

M51, what can you do with this stacked Tiff please?

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Posted (edited)

Practicing from my severely light polluted back garden I know I'm really up against it and my images would definitely benefit from a darker location but while I'm trying to get to grips with my new Skywatcher 250PDS scope, Rebel XS, (1000D), DSLR and controlling everything from Stellarium and Astro Photography Tool my back garden it is! Light pollution aside the potential of my new scope is clear and the detail in the subs / final images are the best I've ever captured but my processing skills also leave a lot to be desired.  I've attached the autosave Tiff file produced directly after Deep Sky Stacker had done it's thing and I will have a go at processing this over the next couple of evenings but would be grateful if some of you lovely people could also have a go and post your results with a brief description of what processing techniques you used as at the moment I really feel that I'm stumbling around with no clear processing sequence / technique. I will be very interested to see how what you achieve compares to my efforts and to learn from you.

Thanks in advance

🙂

Autosave.tif

Edited by FaB-Bo-Peep

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12 minutes ago, alacant said:

Nice shot. Any good?

Cheers

51.jpg.91628f275abe2d4a28748b3c48914078.jpg

That looks amazing thanks! When you have time could you please post a full res version and give me a brief rundown on what you did?

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Posted (edited)

Hi

The book Dark Art or Magic Bullet would be a good read for you.

Or if need something web based look on budgetastro.net and Carol on this forum has a processing tips webpage.

GIMP is free and does a fair bit of Photoshop.

I use StarTools which is powerful but inexpensive.

Edited by happy-kat
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Posted (edited)

I got this with StarTools:

M51-SGL.jpg.3bcae0988db2683631cf04e34df7ec22.jpg

 

In black and white is even better (residual gradient can be reduced even more):

 

M51-SGL-BW.jpg.c9722edb2f019b2e1f138e4b069c75d7.jpg

My workflow was:

Autodev -> Wipe -> Autodev -> Crop ->Deconvolution -> Color -> Life (Less=More 75%) -> Life (Isolate 75%) ->Bin 50% -> Contrast 75% -> Stop Tracking Final Noise Reduction -> Sharp (Large 25%) -> Contrast 75%.

BTW, very heavy gradient: I image from the balcony in downtown Turin, which is a 900K inhabitants city, and I never got such a nasty one. Maybe you could try to shield the scope with some cardboard divider or something like that.

Edited by AltAzAstro
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With startools would be better to Crop first then Bin then process. You want to bin with the most unchanged data but with no artifacts from stacking.

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I cropped first, just added now in the flow, about bin you are right, even if I never found dramatic differences.

 

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Posted (edited)

WIth binning right at the beginning ... there is more gradient left on the top:

 

M51-SGL-2.jpg.1ac7fa3c37ebd5ba3f2a3e4eea85e8be.jpg

 

M51-SGL-2-BW.jpg.d8b2187268ef5cbf1e70995feb135d6c.jpg

 

I

Edited by AltAzAstro

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+1 for this book

2 hours ago, happy-kat said:

The book Dark Art or Magic Bullet would be a good read for you.

 

Quick play with PS. Think I may have over stretched a tad

Autosave-(2).jpg

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Since I shot m51 recently, I gave a shot at processing your data too. Here it is, although I did't do a great job with the synthetic flat.

Autosave.thumb.jpg.898abea1752352308211970763f47823.jpg

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This time using Astro Pixel Processor to reduce light pollution, instead of the Wipe function of Star Tools.

M51-SGL-4.thumb.jpg.b69299f8e89a1124b657e01c868c4f88.jpg

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A quick process in StarTools then using Infanview saved as png, my monitor is fairly calibrated so it might look dark on a none tweaked monitor.

It would be useful to know how many lights and calibration files were used in a stack, I couldn't find much blue but am not sure if that is down possibly to number of lights taken.

There was strong vignetting which flats should help with but it was a nice image to process.

1884821845_Autosave(1.1).png.2c257c147db6105e105aec6557ff51ba.png

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Very nice, @happy-kat. There is indeed a strong vignetting pattern in the background. I wonder if flats were used at all. I also found a strong gradient from left to right. Light pollution, most likely. Getting the blue to reveal itself is quite a challenge. Only one remark regarding your image. For my taste, the background is a bit too flat. It will probably look more natural if you leave a little noise in there. That way, you can also show a little more of the tidal structure.

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Thank you and I agree re background but I went for faster approach with the background so lost some of the fainter tidal structure.

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Ok, so here's my version. Processed in PixInsight

Before (STF stretch applied):

Autosave_clone1.thumb.jpg.3821ea1209009bccff6159a9601bf8a2.jpg

After:

M51_FBP190515.thumb.jpg.01ebd98011bf5cccf84923554c86a6b4.jpg

(click to enlarge)

I haven't completely flattened the background. There's still a dark structure to the upper right. But I didn't want to destroy the tidal stream coming from M51B.

Process:

  • crop all stacking artefacts
  • DBE in several stages. First with a few markers to remove the LP gradient. Then with more markers to remove the vignetting. Finally a pass to reduce some of the remaining artefacts.
  • Photometric Colour Calibration, including background neutralisation
  • Extraction of Luminance
  • Arcsinh and masked stretch of the colour image.
  • Various passes of colour saturation with mask to protect the background

On the synthetic luminance:

  • deconvolution (this increased the noise in the lighter parts of the galaxy, but I wanted to reveal more structure here)
  • stretching
  • HDR compression
  • noise reduction (with a 50% lightness mask)

Then LRGB combination followed by chrominance noise reduction.

  • Curves transformation, targeting the b-component in Lab mode, with a lightness mask to protect the background. This step enhances the blue colour in the galaxy
  • Chrominance noise reduction of the background

@FaB-Bo-Peep:

You have a lot of light pollution, consider investing in a filter, eg an IDAS LP filter. When imaging from a light polluted site without filter, you need to increase the total exposure time a lot. For every magnitude in sky darkness that you lose, you need to increase the total imaging time by a factor of 2.5. So, if you image in a Mag 20 area (reasonably dark sky, where you can just see the Milky Way), you need a total exposure of 2.5 hours for every hour exposure in a Mag 21 area (very dark sky). If you image in a Mag 18 area, you need about 15 times as long as in Mag 21.

There is vignetting in your image. Flats will reduce this.

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Thanks everyone, really useful to see your results and read your comments. I've just had a play with Startools and followed a tutorial on Youtube and that's given me a significant improvement without needing to get too technical. It's early days and I will continue to play with Startools over the next couple of days but I'm pretty sure I will be buying a licence. As you cannot save your work in the free trial version I've attached a screenshot of my initial processed image taken with Windows Snipping Tool. Still more practice needed of course but this is easily my best image of M51 to date.

M51-Startools snip.JPG

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Try to use the Color function and select "Cap Green" -> "To  Yellow": that will help to correct for the green dominant. 😉

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Hi,

I can't be totally sure, but it appears to me the dataset has already been non-linearly stretched. If this is the case then, some things like light pollution/gradient removal, color calibration and deconvolution cannot be performed correctly (from a mathematical point of view). StarTools, especially, is sensitive to this, as much of the processing engine effectiveness hinges on being able to reliably track signal evolution from linear source (e.g. 1-to-1 photon counts) to final processed image.

When you save the DSS result, try saving with settings "embedded" rather than "applied". This should give you a dataset that is linear. If you already did this, then the problem may lie somewhere else; be sure to stack only RAW files (e.g. CR2, NEF or ARW files), and do not use any intermediary programs before passing the frames to DSS. And, as everyone else already commented; flats, flats, flats! 😀 They are the single most effective way of improving your datasets (with dithering between frames a close second). Best of all, it's free (just a bit of effort).

Still, nicely done though; galaxies are not easy to capture from a light-polluted environment, and you've actually managed to capture the faint tidal tail! (problem of course is that gradients and unevenness can look like tidal tails as well, that's why flats are so important; they remove the need to engage in subjective processing trickery and let the dataset speak for itself)

Good stuff!

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^ good spot.

Star tools likes best the autosaved fits file with no rgb alignment.

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Thanks again for all the feedback and comments, I'm learning so much. I checked and DSS appears to be defaulting to "embedded" but thanks for mentioning that.  My stack comprises of Large JPEGS so I will need to make sure my DSLR is switched to RAW files for my next project and look at taking some flats. Just had another go this time using a 32 bit FITS file saved from DSS as apposed to a 16 bit TIFF, the file is much larger so must contain more data to start with yes? To me it looks like another step in the right direction but it's all subjective and as each time I process in Startools I'm using slightly different settings, tweaks and the masks so obviously it's impossible to exactly replicate previous results, someone could go mad with all this tweaking, does anyone ever truly finish an image? Anyway one things is for sure, I absolutely love Startools as it makes complex image manipulation so easy, (which is perfect for me). Again the attached is a screenshot of my processed image taken with Windows Snipping tool as I cannot save the processed image in the trial version. Time to go and buy a licence!

M51-Startools snip-3.JPG

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You can save masks and open a mask to use on a reprocess of the same image, if you don't close the star tools session the crop size is retained just remember to bin the same.

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