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FORUMS Photo Sharing & Visual Enjoyment Astronomy & Celestial 
Thread started 16 Nov 2009 (Monday) 14:44
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Deneb area widefield

 
MintMark
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Nov 16, 2009 14:44 |  #1

Here is a widefield picture of the area behind cygnus. It is 11x120s shot at 35mm f2.8 ISO800 on a Canon 1000D with an Astronomik CLS clip filter mounted on an Astrotrac.

This was one of my first real attempts with the filter and I'm really pleased with how much I can see in this picture. There's the North America nebula of course (my first nebulosity) and a little of the pelican too. Above that is M39 and just left and up from there you can see a small black strip leading to the cocoon nebula. Any other sights in there?

I would have shot for longer, but this scene was disappearing over the roof of the house.


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jmx
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Nov 16, 2009 20:57 |  #2

I like it, but its super dark. Was that on purpose?

I stretched the image a bit more, but cant really do much with a compressed 8bt jpeg.


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http://jmx.ls1howto.co​m (external link)Beginner astro shots w/50D
Scopes: 6" Newtonian (750mm f/5), Skywatcher Equinox 80 (500mm f/6.25), AT 8" Newtonian (800mm f/4).
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Adrena1in
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Nov 17, 2009 02:08 |  #3

Wow, that brought NGC7000 out beautifully...wish I knew how to PP my astro-images so well! ;)

Cygnus and the surrounding area is one of my favourite parts of the sky to shoot.


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kostas75
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Nov 17, 2009 03:58 |  #4

Hello MintMark
It would be an interesting project to go to a dark site and try again this target with/without the Astronomik CLS filter. Try an exposure of 10 minutes with the Astrotrac setup and shoot in RAW mode.
I am sure you will be astonished by the result :)
Kostas


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Adrena1in
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Nov 17, 2009 05:44 |  #5

Wonder where the nearest really decent dark site is to Hampshire. Thinking of taking myself on a camping trip somewhere some time.


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MintMark
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Nov 18, 2009 07:25 as a reply to  @ Adrena1in's post |  #6

Jmx your stretching worked really well. I did try stretching it more during the original processing but whenever I emphasised the nebula it also emphasised red halos around many of the stars (CA from the lens I think). Your stretching has brought out some blue patches in the backgound. All I can think is that the jpeg compression for posting removed the halos so it wasn't a problem when stretching it again. I'm using pixinsight LE for curves... what did you do?

Kostas, I did try a 3 minute exposure and the peak was half way across the histogram, so I thought 2m was OK for my polluted location. And much longer than possible without the filter. And yes, I would be astonished at a 10 minute exposure, expecially if there was no trailing! :)

Thanks for the comments. I'll try processing it again. As for trips somewhere dark... it all depends on the weather doesn't it. Still, we have our own dark sky park in Scotland now. I wonder how often it is clear?


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Celestron
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Nov 18, 2009 08:00 |  #7

Very nice Mark .




  
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Nighthound
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Nov 18, 2009 08:53 |  #8

Great work Mark. That's a beautiful part of the night sky.

Your original here shows your red channel clipped, the green and blue are much better. Jmx's stretch nicely recovered some of the red channel. If you place the two images side by side and compare histograms you'll see the change. If you do a test sample of a darkest region of the background you'll see the RGB numbers are quite a bit uneven. If you go for R=25, G=25 and B=25 (or as close as possible) then all else will fall in place.

The more I see Astrotrac images the more I'd like one for a grab 'n go rig.


Steve
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Adrena1in
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Nov 19, 2009 03:16 |  #9

Nighthound wrote in post #9036305 (external link)
The more I see Astrotrac images the more I'd like one for a grab 'n go rig.

Likewise, but I'd still rather try and make a powered Barn Door Tracker myself.


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foxbat
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Nov 19, 2009 06:42 |  #10

Adrena1in wrote in post #9029430 (external link)
Wonder where the nearest really decent dark site is to Hampshire. Thinking of taking myself on a camping trip somewhere some time.

Definitely Wales. The weather can be 'challenging' for camping over there though. The New Forest would be another good bet but not as dark.

(ref: http://www.cpre.org.uk …y/results/light​-pollution (external link))


Andy Brown; South-east England. Canon, Sigma, Leica, Zeiss all on Canon DSLRs. My hacking blog (external link).

  
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MintMark
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Nov 22, 2009 03:12 |  #11

Adrena1in wrote in post #9042099 (external link)
Likewise, but I'd still rather try and make a powered Barn Door Tracker myself.

I really considered building a barn door tracker but, even though I have O-level woodwork :) , I knew I would quickly get frustrated with it. The main problems I thought would be

  • Nuts and bolts. Getting hold of imperial threads for camera and tripod mounting is a bit of hassle.
  • Alignment. You need some way of aligning the hinge with north. I didn't know so much about collimating polar and finder scopes then, so I thought this would be really hard.
  • Accuracy... of the drive. It would only ever be useful for widefield.
So I bought an Astrotrac. I tell my wallet that I am doing my bit to support British (and US) innovation and engineering :)

Mark

  
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MintMark
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Nov 22, 2009 04:35 |  #12

Nighthound wrote in post #9036305 (external link)
Great work Mark. That's a beautiful part of the night sky.

Your original here shows your red channel clipped, the green and blue are much better. Jmx's stretch nicely recovered some of the red channel. If you place the two images side by side and compare histograms you'll see the change. If you do a test sample of a darkest region of the background you'll see the RGB numbers are quite a bit uneven. If you go for R=25, G=25 and B=25 (or as close as possible) then all else will fall in place.

The more I see Astrotrac images the more I'd like one for a grab 'n go rig.

OK, I took the advice from the thread and reprocessed the image. The basic steps I did were

  • Stretiching and gradient removal (same as first attemnpt)
  • Colour balancing the background by adjusting the dark point of each channel's histogram. The CLS filter gives you an image with less red. When you balance it you reduce green and blue and end up with pink stars (or pink halos around stars).
  • Enhanced the nebula. I ended up creating a mask for this by thresholding the red channel and applying a median filter to eliminate the tiny red areas, leaving just the large areas of red. With the mask in place I could boost the red without turning the stars into pink mush.
  • Removed the mask and reduced the red highlights, so the stars with red halos don't look so pink. Having said that, the jpeg compression seems to take out the star colours anyway.
Thanks for all your suggestions and help.


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