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Update: 3rd June Re-processed to remove slight magenta tint caused by the non-uniform removal of light pollution by the DBE process ( it was being fooled by the very bright image centre ).

The weather here has been quite bad for a while now ( thunderstorms most nights and otherwise cloudy ), so, for something to do, I went back to the original exposures I captured of Omega Centauri back

Thank you all very much for your very kind comments - I am so pleased you liked my new image. Cheers Mike    

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18 hours ago, Atreta said:

Fantastic image. 

 

17 hours ago, celestron8g8 said:

That is just about as Awsome as you can get ! Great capture !

 

17 hours ago, swag72 said:

Wow, wow and wow..... and double wow!!! That's superb :) 

Thanks Guys, much appreciated :)

 

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I have for some time been trying to understand what is the source of the coloured "stripe" that I get across bright stars in my images.  In particular, is it a result of defects in the optical system or  processing artefacts or maybe a little of both?

It is complicated because I think I might have at least two contributing issues ...

1. I do have a problem with astigmatism, either in the scope or the coma corrector or both.  It is not usually too bad as it is masked by normal seeing conditions and really only shows up during focusing ( when the round stars become oval when out of focus and the orientation of the oval rotates 90 deg when changed to the other side of focus ) except when seeing is extrodinary, eg. as can be seen in the image below - with crosses appearing in the in-focus stars.

8592E919-2282-47D2-8D23-B39CA863E1DA.jpeg.dc19e352e565c1ec36a3d50edd26b3ec.jpeg

2. But I have another probelm that shows up sometimes - a coloured line across the in-focus stars.  As can be seen in this 100% crop of this image of Omega Centauri ( left hand image )

10D718DE-089F-4DDD-A082-36E467CC1B0F.jpeg.1120156de5f06c8dcae98f257432740e.jpeg F5D8FC9D-D133-4886-A7E0-95071857EA98.jpeg.f8ae3472fb6a889f6759d24672648883.jpeg

                                        ( old workflow )                                                                          ( new workflow )

I decided to see if I could improve the stars by changing the way I calibrate and colour balance my images.  The result is maybe a slight improvement ( or It may just be the result of different contrast reducing the appearance ).

Now I look at them together I suspect it may just be the different stretch / deconvolution between the two images and the 'stripe' is probably just the same.  I am also tending to think now that it is really just a manifestation of the astimatism problem.

Anyway, here is the new version of Omega Centauri with the new workflow - plus every so slightly different colour balance and stronger deconvolution ..

1277454240_globulastarclusteromegacentauri(ngc5139)inhdr2018v2(2732wide)compressed.thumb.jpg.1afb51e9065bd7811c431375c13ca6ed.jpg

Globular cluster, Omega Centauri ( NGC 5139 )  ( please click / tap on image to see larger and sharper )

Edited by MikeODay
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Mmmm, I can't decide now if I prefer the 1st or 2nd versions :) - what do you think?

746C585E-6C62-4D30-818B-856E2074EA6A.jpeg.b6c2f6739aa6a8e698c0b572f9427f2c.jpeg

282EDD48-A56A-4E0D-B2E1-7B7603B22330.jpeg.571c5fcd19eb511afe42dec5c3407552.jpeg

......

The new one is brighter ( due to slightly different stretch but also a little stronger deconvolution resulting in brighter stars ).  It also does not suffer from the strong residual red background in the first - and as a result it looks a little greener by comparison.   The colours are richer in the first and overall I think I might prefer the colour balance of the first ( even thought I suspect that it is less realistic ( a lttle too magenta I think ).  Anyway, I'd love to hear your thoughts and get the benefit of different eyes that have not stared at the images for too long :)

 

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Looking from my iphone i like the first one better , brightness of second one drowns some of the center stars and i personally prefer to see all center stars as much as possible . Also i think the colors are slightly better in the first one . Too much brightness drowns color . 

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Mike,

1st, although the cluster appears smaller the image has an overall better balance the surrounding star field invokes more feeling to the central cluster kinda huge & powerful yet isolated even lonely.

Feelings are what you want from an image when you view it!

Great work.

Peter

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16 hours ago, celestron8g8 said:

Looking from my iphone i like the first one better , brightness of second one drowns some of the center stars and i personally prefer to see all center stars as much as possible . Also i think the colors are slightly better in the first one . Too much brightness drowns color . 

 

16 hours ago, cuivenion said:

First one for me too.

 

15 hours ago, whipdry said:

Mike,

1st, although the cluster appears smaller the image has an overall better balance the surrounding star field invokes more feeling to the central cluster kinda huge & powerful yet isolated even lonely.

Feelings are what you want from an image when you view it!

Great work.

Peter

Thanks guys - a clear consensus  for the 1st version!

Cheers

Mike

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3 hours ago, Mr Spock said:

The seconds one has merits, but the first gets the inner core detail. If you could get the best of both... ?

Yes I think you may be right ...

This is a capture of the results of a google search for images of Omega Centauri, the image on the top right is the first one from this thread.

629844CB-EA45-4529-8C8D-0001CAADC49A.jpeg.0b3d0025d78c28d01beb4d813341fc78.jpeg

Compared to some of the other images, particularly the ESO image on Wikipedia, mine has subtle but definite hint of magenta.  I will have another tweak and, as you suggest, see if I can keep the best of both.

Cheers

Mike

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You can do a composite of both and see how it comes out . You can also do a selection of the core , do feather for 2 count , right click and copy , and paste on the second image . Be sure to feather to make it look right . Would be interesting . 

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9 minutes ago, celestron8g8 said:

You can do a composite of both and see how it comes out . You can also do a selection of the core , do feather for 2 count , right click and copy , and paste on the second image . Be sure to feather to make it look right . Would be interesting . 

Thanks Ron, good suggestions.   I'll have a go tomorrow - I should really put the Ipad down now - time to dream  ?

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Ok, here is the new version.

I found the problem that was causing the slight magenta tint - the DBE process was having some difficulty with the very bright central portion and was not correctly removing the light pollution that is constant across the frame.  I fixed that and then merged the results back into the previous versions ( heavily weighted to the latest version ).

1822684557_globulastarclusteromegacentauri(ngc5139)inhdr2018v3(2732wide)compressed.thumb.jpg.b87b20181680fe71f8cd3c5b6dcf3033.jpg

The globular star cluster Omega Centauri ( NGC 5139 ) in Centaurus  ( please click / tap on image to see full size )

And here is the original version from the top of the thread:

1450464857_globulastarclusteromegacentauri(ngc5139)inhdr2018v1(2732wide)-compressed.thumb.jpg.a4c0a922ccba37b730bd4d75c02bfe13.jpg

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On 05/06/2018 at 19:08, Jkulin said:

The new version Mike is superb, really love that, jealous or what ?

 

13 hours ago, Highburymark said:

I'm visual only and just stumbled across this thread. It's one of the most stunning images I've ever seen. Thanks for sharing your amazing work Mike

 

Thanks guys, that is very kind of you.

Cheers

Mike

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  • 6 months later...

The weather here has been quite bad for a while now ( thunderstorms most nights and otherwise cloudy ), so, for something to do, I went back to the original exposures I captured of Omega Centauri back in the middle of the year and re-processed them with the aim of trying to improve the colour balance and also bring out the faint stars a little better.

What do you think?

308841029_OmegaCentauri(NGC5139)-IPADPro-compressed2.thumb.jpg.e6704811b1d0756c7eee8a5c81fd722d.jpg

The globular star cluster Omega Centauri ( NGC 5139 ) in Centaurus  ( please click / tap on image to see larger )

The full size image can be found here

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Mike, they're all superb, but that final version really wins it for me. The slight red/magenta cast has gone and every star right through the core is resolved. Viewing the full size version on Flickr is simply amazing....:thumbright:

Cheers, Geof

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18 hours ago, Mark at Beaufort said:

It looks brilliant to me Mike.

 

17 hours ago, geoflewis said:

Mike, they're all superb, but that final version really wins it for me. The slight red/magenta cast has gone and every star right through the core is resolved. Viewing the full size version on Flickr is simply amazing....:thumbright:

Cheers, Geof

 

Thanks Guys, much appreciated.

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