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Barnard's Galaxy ( NGC 6822 ) in the constellation Sagittarius

 

image.jpeg

 

( click on image to see larger )

 

Barnard's Galaxy is one of a number of dwarf galaxies relatively near to us in our Local Group of galaxies. Similar in structure to the Small Magellanic Cloud, Barnard's galaxy is thought to be about half the size and around eight times as far away at 1.6 M Light Years. 

Weather permitting I hope to add more subs to help bring the faint detail further out from the sky background.

Details:

Barnard's Galaxy ( NGC 6822 ).
Skywatcher Quattro 10" f4 Newtonian telescope.
Skywatcher AZ Eq6 GT Mount.
Orion 80mm f5 guide scope and auto guider - PHD2.
Baader MPCC Mark 3 Coma Corrector, no filter.
Nikon D5300 (unmodified).
Field of view (deg) ~ 1.35 x 0.90.
ISO400, 14bit NEF, Long Exp. NR on.
40 x 180sec (1/3 before & 2/3 after zenith) 25 Aug 16.

Processed in PixInsight and finished off in Photoshop.

Links:
https://500px.com/MikeODay
http://photo.net/photos/MikeODay

 

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Great image of this faint target. And excellent write-up.

You have faint colour in the stars. I think that with carefull processing, you could bring out more colour. That would make this image a winner, IMO.

I would love to have a go at this myself sometime, but I would have to cut down trees to be able to see it. :p

Thanks for sharing

Edited by wimvb

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2 hours ago, wimvb said:

Great image of this faint target. And excellent write-up.

You have faint colour in the stars. I think that with carefull processing, you could bring out more colour. That would make this image a winner, IMO.

I would love to have a go at this myself sometime, but I would have to cut down trees to be able to see it. :p

Thanks for sharing

Thanks Wim, much appreciated.

I had another go at the processing to increase the saturation and also to raise the contrast in the shadow areas.. Results below ...

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Tweaked processing to increase saturation in the stars and to raise the contrast in the shadow areas ...

 

image.jpeg

 

oh, and a tad warmer colour balance in the highlights as well.

 

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The re-processed version further highlights the light and dark areas across the frame.   Is anyone familiar with this area of space and do you know if the effect in my image is real or if it more likely to be a processing artifact?

I'm pretty sure that the darkness in the extreme corners is due to imperfectly corrected vignetting but I'm less sure about the other dark and light areas.

Edited by mike005

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Gradients in an image are usually, well, gradual. If there is any detail present, it's probably a real albeit very faint, structure. In your image, I would agree that the dark corner is an artefact, while the rest may very well be structure. One way to better detect structure is to inverse the luminance (make a "negative") and stretch this. Black stars on a light bacground can help reveal very faint data.

When using DBE on images with faint structures, I sometimes make a copy of the image. I then stretch to the extreme and use this copy to place samples for dbe. I then drag an instance of this dbe to the workspace. I close dbe and apply the instance on the workspace to my original image. This way it's easier to avoid placing samples over real structure.

Very faint background structure can be revealed by carefull stretching. Masked stretch is usually the best alternative for a first stretch. Using exponential transform (exponential stretch), can bring out really faint detail.

See this example (scroll down the thread)

http://pixinsight.com/forum/index.php?topic=9649.0

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Thanks Wim for your very detailed and helpful reply.  I'm still fairly new to Pixisight and your suggestions are much appreciated.  

Cheers

Mike

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9 hours ago, wimvb said:

Gradients in an image are usually, well, gradual. If there is any detail present, it's probably a real albeit very faint, structure. In your image, I would agree that the dark corner is an artefact, while the rest may very well be structure. One way to better detect structure is to inverse the luminance (make a "negative") and stretch this. Black stars on a light bacground can help reveal very faint data.

When using DBE on images with faint structures, I sometimes make a copy of the image. I then stretch to the extreme and use this copy to place samples for dbe. I then drag an instance of this dbe to the workspace. I close dbe and apply the instance on the workspace to my original image. This way it's easier to avoid placing samples over real structure.

Very faint background structure can be revealed by carefull stretching. Masked stretch is usually the best alternative for a first stretch. Using exponential transform (exponential stretch), can bring out really faint detail.

See this example (scroll down the thread)

http://pixinsight.com/forum/index.php?topic=9649.0

I also posted the question about the light and dark parches to the Image Processing help forum and Andrew Luck kindly posted the image below and there is some structure in the background.

image.jpeg

Cheers

Mike

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Nice image. It's always very informative to see what others can do with one's data. While looking at your reprocessed images, I thought I saw structure in the background, but this differs from the structure revealed by Andrew Luck.

I've found that dbe can be a very tricky process when applied to a rich starfield. Sometimes it can result in a background with a false structure.

You could try searching for wide field images of this area on google. Maybe there are images that confirm your results.

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8 hours ago, wimvb said:

Nice image. It's always very informative to see what others can do with one's data. While looking at your reprocessed images, I thought I saw structure in the background, but this differs from the structure revealed by Andrew Luck.

I've found that dbe can be a very tricky process when applied to a rich starfield. Sometimes it can result in a background with a false structure.

You could try searching for wide field images of this area on google. Maybe there are images that confirm your results.

Yes still not sure about the structure.. I'm in the middle of re-processing with different DBE settings and I'll see what I end up with.

Cheers

Mike

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6 hours ago, peter shah said:

you can certainly see the faint stuff in the background, a beautiful object well imaged

Thanks Peter, much appreciated.

Cheers

Mike

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I have re-processed the image with improved removal of vignetting and more uniform background extraction...

 

Barnards Galaxy ( NGC 6822 ) in Sagittarius - v2a compressed.jpg

 

And here is a more heavily stretched version compared to a downloaded DSS image ...

 

Untitled-1d small.jpg ( my image )

dss_ngc6822_r small.jpg ( DSS image )

 

Given the different filters/cameras/processing ( and of course far better image from very dark skies, large scope, etc ) I think the background structure is similar enough to say that it is real in my image and not just a DBE artifact.

Edited by mike005

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Great result! Definitely a winner, in my book.

You could experiment with masked exponential stretch of the background to reveal even more, but you run the risk of starting to stretch the noise.

The way I learned PixInsight was to post an image I got stuck with as a processing challenge on the PixInsight forum. I got some great feedback which kept me busy for months (on and off) learning and trying to replicate results from others. The forum, and Alejandro Tombolinis website are a great place to learn PI.

Good luck.

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Super image of a not often seen target now added to my list of must gets though a little low on the horizon now - thanks.

Do you have ability to add HA think that would really help with the structures.

Paddy 

 

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12 hours ago, wimvb said:

Great result! Definitely a winner, in my book.

You could experiment with masked exponential stretch of the background to reveal even more, but you run the risk of starting to stretch the noise.

The way I learned PixInsight was to post an image I got stuck with as a processing challenge on the PixInsight forum. I got some great feedback which kept me busy for months (on and off) learning and trying to replicate results from others. The forum, and Alejandro Tombolinis website are a great place to learn PI.

Good luck.

Thanks Wim.

I did try exponential stretch but it did not fit in very well with my current workflow; I think my repeated use of masked stretch has already heavily weighted the stretch to the first few bits and there was not much left to extract and resulted in a blotchy overstretched background.  I will have to experiment some more.

Cheers

Mike

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11 hours ago, PatrickGilliland said:

Super image of a not often seen target now added to my list of must gets though a little low on the horizon now - thanks.

Do you have ability to add HA think that would really help with the structures.

Paddy 

 

Thanks Paddy, much appreciated.

No I am not able to concentrate on just the HA.. I have an unmodified DSLR and I do not have any narrow band filters.. In any case, my mount has a problem tracking in DEC so I turn it off; the longest subs I can take without obvious errors in DEC is about 3 to 4 minutes and I think I would need a fair bit longer than that with a narrow band filter.

Cheers

Mike

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