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Old 29-08-2020, 06:27 PM
FrancoRodriguez (Franco)
Franco

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yet another helix nebula

Hi All, here's my rendition of the helix nebula. It definitely goes into the "purty pitchers" category, certainly not an unadulterated pure science image, but I wanted something that looked nice because I'm pretty new to pure narrowband imaging.
I went pretty deep with around 50 x 20 minute exposures in order to get the outer wisps in Ha. I used Ha luminance layer and red channel, oxygen for blue and green, and sulphur for green too (not many sulphur photons).
Weighted batch preprocessing in pixinsight
the rest done with layers in PS and LR
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Old 30-08-2020, 06:04 AM
Placidus (Mike and Trish)
Narrowing the band

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Welcome



First up, the depth is amazing! You've got the largest of the super-faint outer chevrons, and the still-fainter ones are starting to show. Excellent bordering on remarkable.



Mapping H-alpha to red and OIII to blue-green is legit and solid.



Using H-alpha as a luminance layer is fraught with traps. The most obvious is any area that is a pure lovely brilliant OIII with no H-alpha will come out black.


You mentioned that the SII was scanty, and that makes it hard (but not impossible, given the great depth you've achieved) to do an SHO rendition without ending up with bloated red rings round the stars from the SII.



One very labour intensive way around (routine for us for all narrowband images) is to separate the image into stars and nebulosity. You can then process the stars and the nebulosity (which is the important thing!) completely separately, getting the colour balance right in the nebulosity, applying sharpening and then reassembling (just adding the two together again).



Much quicker and easier (but not our favourite approach): I'd suggest that you either scrap the SII, or perhaps map it to its natural red if you don't want to throw it out, and you'll have a nice almost-natural-colour narrowband image.


Very best,Mike
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Old 30-08-2020, 09:09 AM
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Cosmic (Daniel)
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Nice work Franco, big fan of the outer nebulosity captured.
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Old 30-08-2020, 05:26 PM
FrancoRodriguez (Franco)
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I really appreciate the feedback. HSO is very new to me (I've usually just enhanced OSC images with narrowband data). It's a lot harder than I had imagined. I think I understand what you mean regarding Ha as luminance. Would one way around the problem be to make two images, One with Ha lum layer and the other without, and get those two separate images, make them layers themselves and use one of the purely additive blending modes? I'm not happy with the lack of detail in the inner portion of the image. I lost a lot of the subtle oxygen radial streaming data. It's all pretty new to me. can I show you the original mono images?
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Old 30-08-2020, 05:33 PM
FrancoRodriguez (Franco)
Franco

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Here they are. I put them through masked stretch and linear fit. How would you recommend I improve the streaky oxygen (Bok globule?) data? I had to compress the hell out of the files to 1mb otherwise it wouldn't let me upload them
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Old 02-09-2020, 06:11 PM
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codemonkey (Lee)
Lee "Wormsy" Borsboom

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Nice work Franco, you brought out a lot of very faint detail there!
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Old 02-09-2020, 08:06 PM
topheart
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Very nice!
Wonderful faint stuff there!

Cheers,
Tim
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Old 07-09-2020, 09:29 PM
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ChrisV (Chris)
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There's a lot of getting detail coming through. Well done!
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