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alan4908

Bubble nebula (NGC7635)

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I decided to go for an LRGB rendition of the Bubble nebula since the red channel is relatively bright. I extracted the data mainly from the various test shots of my new unguided imaging setup (an Esprit 150 on a GM1000HPS) which gives 0.7 arc seconds/pixel with my CCD. Having run yet more V-curves with FocusMax, to improve my focusing precision, I'm now of the opinion that my seeing is much better than I had previously thought, last night it was below 2 arc seconds, so having a low plate scale should help resolve DSO details. The image below represents just over 4 hours of integration time.

Alan

 592fcb5bd0c59_30.Final.thumb.jpg.28e2c67f0ea81e5355d3149f43da92d6.jpg

LIGHTS: 8; R:6: G:5: B:7 x 600s. DARKS:20; FLATS:40; BIAS: 100 all at -20C.

 

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Nice to see this level of detail,

it has come out very nice indeed.

well done

Paul

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Thanks for all the comments guys, which are much appreciated :hello:

Alan

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53 minutes ago, PatrickGilliland said:

Nice work Alan, I found this a tougher than expected target in LRGB, so i am impressed :)

Thanks Paddy. I too like the result, the only (minor) issue that I have with the image is that some of the stars within the red nebulosity are a little too purple for me. They started off magenta which I reduced within PS, using selective colour and Hue/saturation. However, I found that if I reduced the magneta too much, the result didn't look correct, so I settled on a compromise of purple/blue. If you have any tips for a better magenta reducing strategy,  please let me know !

Alan

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34 minutes ago, alan4908 said:

Thanks Paddy. I too like the result, the only (minor) issue that I have with the image is that some of the stars within the red nebulosity are a little too purple for me. They started off magenta which I reduced within PS, using selective colour and Hue/saturation. However, I found that if I reduced the magneta too much, the result didn't look correct, so I settled on a compromise of purple/blue. If you have any tips for a better magenta reducing strategy,  please let me know !

Alan

In PS short of what you are doing no.  In PI yes have a little pixel math formula for this very issue.  There is a tool that can help also but I have totally forgotten what it's called!  Uses catalogues to look up star colour and calibrates based on that.  I think that is PS based too.

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Very obviously there's an awful lot to like in this image. :icon_salut: I do have a reservation based on Harry Page's astute critiques of my own pictures a while back, though. He objected that my stellar cores were burned to white. I see this here. Since then I've been careful in applying luminance to stars, and tried to find ways of keeping it out of the brighter ones.

Olly

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2 hours ago, PatrickGilliland said:

In PS short of what you are doing no.  In PI yes have a little pixel math formula for this very issue.  There is a tool that can help also but I have totally forgotten what it's called!  Uses catalogues to look up star colour and calibrates based on that.  I think that is PS based too.

Thanks Paddy - I shall have a look at PI a little more for a possible solution.

2 hours ago, ollypenrice said:

Very obviously there's an awful lot to like in this image. :icon_salut: I do have a reservation based on Harry Page's astute critiques of my own pictures a while back, though. He objected that my stellar cores were burned to white. I see this here. Since then I've been careful in applying luminance to stars, and tried to find ways of keeping it out of the brighter ones.

Olly

Thanks for the comment Olly - yes, I'd like less white cores, which as you say are caused by the additive effect of the Lum, I shall experiment a little more - thanks for the critique and tip ! 

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8 hours ago, alan4908 said:

Thanks Paddy - I shall have a look at PI a little more for a possible solution.

Thanks for the comment Olly - yes, I'd like less white cores, which as you say are caused by the additive effect of the Lum, I shall experiment a little more - thanks for the critique and tip ! 

If you have PI then no need to look, just run the formula below

2017-06-04_08-06-41.png.5dd827614f2b65c50ab0a79a48ae76f6.png

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After experimenting with various ways to make my star cores less white, I decided on a two stage technique:

i) To stretch the Luminescent layer for the moderately bright stars slightly less, this reduces their size and allows more colour. 

ii) After watching an Adam Block processing tutorial: to shrink the moderately bright stars slightly via the Pixinsight Erosion filter (eg Morphological Transformation) with the Kernal filter set to a 5x5 diamond option, rather than a circular shape. 

After working out how to program Pixinsight with Pixelmath functions and trying various options to reduce the magenta, I still didn't like the result, however, I also found that I'm getting more partial to slightly purple stars :happy11:

Alan

593932b54f27a_40.Final-reprocessed.thumb.jpg.3f17a9d3a7e04c38a400c705d409aef3.jpg

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