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M101 - The Pinwheel Galaxy

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18 replies to this topic

#1 BackyardSpaceDude

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Posted 02 June 2020 - 03:34 PM

Looks like that's it for clear nights for the foreseeable, so I've decided to call this finished. Although as usual I'll probably tinker again...

 

49964078973_89d3c0248b_k.jpg

 

64x 600s (10hrs 40mins) ISO800
19x 600s (3hrs 10mins) Ha 12nm ISO800
SW 80ED DS-Pro
Canon 60D (CentralDS)
SW NEQ6


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#2 Chris_Mammendorf

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Posted 02 June 2020 - 06:59 PM

The contrast of the black sky and the pinkish H-alpha-regions is very strong - wonderful! And there are many other galaxies on the pic - so many details in M101 itself. Thanks for showing! 10 hours + 3 hrs – what an effort! But obviously it was worth it.

 

Greetings,

Chris


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#3 chrysalis

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Posted 02 June 2020 - 07:04 PM

Superb image!


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#4 BackyardSpaceDude

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Posted 03 June 2020 - 05:55 AM

Thanks Chris and Mark! Quite happy with it myself, but if anyone has some tips on how it can be better, let me know!



#5 Starman27

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Posted 03 June 2020 - 10:06 AM

I really like this image.


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#6 sunnyday

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Posted 03 June 2020 - 12:00 PM

wow , nice photo.

very nice details and colors on a black sky .

thanks .


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#7 chanrobi

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Posted 03 June 2020 - 12:29 PM

Is the pinkish colour realistic?


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#8 F.Meiresonne

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Posted 03 June 2020 - 05:01 PM

i guess not, but in AP one never knows...

 

You can pull out quite some colors, if you like you could get a green one,or a  red one or....etc

 

 

I never understood this...

 

I was a visual observer for year. No color , there....

 

But in AP you see so much more detail in incredible small apertures.

 

It got me hooked..

 

So strange colors pink also to me , but alot of detail there though...


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#9 chanrobi

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Posted 03 June 2020 - 05:05 PM

i guess not, but in AP one never knows...

You can calibrate images for colour as how it would appear?

 

https://clarkvision....ost-processing/


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#10 BackyardSpaceDude

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Posted 03 June 2020 - 05:39 PM

Is the pinkish colour realistic?

 

You can calibrate images for colour as how it would appear?

 

https://clarkvision....ost-processing/

I do really struggle with colour balance in my images. My DSLR is modified so it's always a little more red, but recently I've moved to Siril for stacking, and when the stack comes out it's massively green. In post I start by trying to balance the colour histogram in levels, use gradient exterminator and play about in curves until it looks right to me, but invariably I can't get it perfect. So thank you very much for that tutorial, that will come in handy!

 

I'm happy that the pinkish areas stand out though - that's the Ha data coming through.



#11 BQ Octantis

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Posted 03 June 2020 - 07:31 PM

I do really struggle with colour balance in my images. My DSLR is modified so it's always a little more red, but recently I've moved to Siril for stacking, and when the stack comes out it's massively green. In post I start by trying to balance the colour histogram in levels, use gradient exterminator and play about in curves until it looks right to me, but invariably I can't get it perfect. So thank you very much for that tutorial, that will come in handy!

 

I'm happy that the pinkish areas stand out though - that's the Ha data coming through.

I've switched to RawTherapee for color calibration in linear color space. I've found that the red in my 600D/T3i is also significantly overdriven. To first order, the red, green, and blue channel histogram peaks should line up. The dual log-scale histogram in RawTherapee makes it easy to line them up with RGB Curves. And in linear color space, you just need to adjust the endpoints of the lines. For my 200mm f/2.8, I found I can't do just white point or black point. So instead, I lower the red's white point until the histograms line up. I then take it halfway back to 100. I then move the red's black point to the right (control-drag for fine increments) until they line up again. Over a session, the red overdrive increases slowly with the sensor's temperature increase. So for a series of lights, I adjust the RGB Curves for the image closest to the middle of the session and apply that to the rest. This seems to average out the drift; if it doesn't (rare), I'll tweak the stacked TIFF in RawTherapee before attacking it in Photoshop.

 

BQ


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#12 BackyardSpaceDude

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Posted 04 June 2020 - 04:45 PM

That’s interesting, thank you! Is the main benefit of RawTherapee in this example the improved histogram control over the one in PS?



#13 Readerp

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Posted 04 June 2020 - 05:16 PM

You can calibrate images for colour as how it would appear?

 

https://clarkvision....ost-processing/

Appear to whom? Always a bit problematic.

 

Deep sky object appear black and white to humans mostly. 



#14 BQ Octantis

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Posted 04 June 2020 - 05:22 PM

That’s interesting, thank you! Is the main benefit of RawTherapee in this example the improved histogram control over the one in PS?

RawTherapee has many, many useful tools. The ones I use:

 

  • Darks calibration
  • Flat calibration (with a single flat)
  • Fine color calibration (Photoshop has 255 levels, RT has 5,556)
  • Several DeBayer algorithms (one good for stars, one good for DSOs)
  • Outstanding chromatic aberration removal (with more control than Adobe Camera Raw)

 

And on my old limited data, by following the Roger Clark protocol (particularly using the various noise filters) I can get results worthy of print.

 

BQ



#15 tmyers

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Posted 04 June 2020 - 06:02 PM

Looks like that's it for clear nights for the foreseeable, so I've decided to call this finished. Although as usual I'll probably tinker again...

49964078973_89d3c0248b_k.jpg

64x 600s (10hrs 40mins) ISO800
19x 600s (3hrs 10mins) Ha 12nm ISO800
SW 80ED DS-Pro
Canon 60D (CentralDS)
SW NEQ6

How many sessions, nights did it take you to gather that much data?

Sent from my SM-N970U using Tapatalk

#16 tmyers

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Posted 04 June 2020 - 06:05 PM

I am not seeing an image on my phone

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#17 BackyardSpaceDude

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Posted 09 June 2020 - 05:00 AM

RawTherapee has many, many useful tools. The ones I use:

 

  • Darks calibration
  • Flat calibration (with a single flat)
  • Fine color calibration (Photoshop has 255 levels, RT has 5,556)
  • Several DeBayer algorithms (one good for stars, one good for DSOs)
  • Outstanding chromatic aberration removal (with more control than Adobe Camera Raw)

 

And on my old limited data, by following the Roger Clark protocol (particularly using the various noise filters) I can get results worthy of print.

 

BQ

Amazing, strong recommendation! I'll give it a go.

 

 

How many sessions, nights did it take you to gather that much data?

Sent from my SM-N970U using Tapatalk

5 nights, one of them for Ha, and one was purely for darks and my USB hub broke just before my session started.



#18 poobie

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Posted 09 June 2020 - 09:33 PM

I do really struggle with colour balance in my images. My DSLR is modified so it's always a little more red, but recently I've moved to Siril for stacking, and when the stack comes out it's massively green. In post I start by trying to balance the colour histogram in levels, use gradient exterminator and play about in curves until it looks right to me, but invariably I can't get it perfect. So thank you very much for that tutorial, that will come in handy!

 

I'm happy that the pinkish areas stand out though - that's the Ha data coming through.

Since you're already using Siril to stack, you might want to give its photometric color calibration tool a try as well - as I understand things, it plate solves the image, and uses the color of the known stars to set the color balance to something closer to real life.  


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#19 BackyardSpaceDude

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Posted 13 June 2020 - 02:45 PM

Since you're already using Siril to stack, you might want to give its photometric color calibration tool a try as well - as I understand things, it plate solves the image, and uses the color of the known stars to set the color balance to something closer to real life.  

Fantastic, thank you! I had no idea.


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