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[RCC] Jellyfish SHO +RGB Stars

SHO Request for feedback Sh2-248 IC Objects
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Andreas avatar
Andreas avatar
Hello everyone,

I would like to present my image of the Jellyfish Nebula here. 

https://app.astrobin.com/i/spubzv

I always try to present the narrowband images as naturally as possible. The color contrast is not too high, but the different areas of Sii, Ha and Oiii should still be visible.

For me this is my best shot and image processing so far and that's why I want to show it here to take your suggestions. 

CS 
Andreas
Chase Davidson avatar
Chase Davidson avatar
Beautiful shot Andreas. I like how you kept the contrast to a natural state. I find myself over saturating my shots many times because I have the ability to show off the different gasses. I will try to learn from you.

Clear skies!
Chase
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Noah Tingey avatar
Noah Tingey avatar
Looks super cool. The change from revision A to B was a good one. If I had to give one critique, I would say that you could pull more color out of your stars. IC443 has a cool blue and golden color contrast – I think bringing out the gold and blue stars would complement that well. But overall great photo.
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Kyle Goodwin avatar
Kyle Goodwin avatar
It's a great image.  I have some critiques, but they're fairly minor:
1. I think the background is a tad too bright and the noise reduction could be just slightly more.  Sorry, I just checked your integration time.  The noise level is actually very good for the length of integration here.  I'd recommend somewhat more integration if you want an even cleaner background and it might also be that some noise was caused by gradient extraction.
2. The star shapes seem somehow slightly unnatural to me.  I wonder if BlurX shrank the stars quite a bit without having much effect on the diffraction spikes leading to this look?  Some of the stars look almost diamond or squareish.  You have a lot of RGB exposure time.  I might try culling that pretty aggressively to the best 30 frames of each color and using that for the stars so you don't need to BlurX the stars or at least can do it less aggressively, assuming you're processing the stars separately.
3. Your stars lack color, which happens in the natural course of things unless special care is taken to stretch them separately and less aggressively, increase their saturation, etc.  With the amount of RGB exposure you have I'm confident you have the data to support beautifully colored stars in this image.
4. Stars near the edges of the field seem to have an extra set of diffraction spikes rotated 45 degrees from the main set, which I don't seem to see near the center of the image.  I'm not sure what's causing that.

As you can see, my main recommendation would be to focus on improving your stars.  I think the nebulosity and general processing is excellent.  The stars will be the next level up for your images.  You're doing great work!
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Andreas avatar
Andreas avatar
Kyle Goodwin:
It's a great image.  I have some critiques, but they're fairly minor:
1. I think the background is a tad too bright and the noise reduction could be just slightly more.  Sorry, I just checked your integration time.  The noise level is actually very good for the length of integration here.  I'd recommend somewhat more integration if you want an even cleaner background and it might also be that some noise was caused by gradient extraction.
2. The star shapes seem somehow slightly unnatural to me.  I wonder if BlurX shrank the stars quite a bit without having much effect on the diffraction spikes leading to this look?  Some of the stars look almost diamond or squareish.  You have a lot of RGB exposure time.  I might try culling that pretty aggressively to the best 30 frames of each color and using that for the stars so you don't need to BlurX the stars or at least can do it less aggressively, assuming you're processing the stars separately.
3. Your stars lack color, which happens in the natural course of things unless special care is taken to stretch them separately and less aggressively, increase their saturation, etc.  With the amount of RGB exposure you have I'm confident you have the data to support beautifully colored stars in this image.
4. Stars near the edges of the field seem to have an extra set of diffraction spikes rotated 45 degrees from the main set, which I don't seem to see near the center of the image.  I'm not sure what's causing that.

As you can see, my main recommendation would be to focus on improving your stars.  I think the nebulosity and general processing is excellent.  The stars will be the next level up for your images.  You're doing great work!



Thank you so much for your detailed and constructive feedback – I really appreciate it!
    [*]
    Regarding the background, you're absolutely right – with more integration time, there's definitely room for improvement. I'll try to increase the total integration time in the future and be a bit more careful with gradient removal.
    [*]
    The diamond-like shapes are mostly a result of the GHS stretching process – and they're actually intentional. I was going for a look that resembles the kind of star shapes you see in images taken with a Takahashi Epsilon, which I personally find very appealing.
    [*]
    You're spot on about the lack of star color – that’s definitely something I want to improve. I do have the RGB data, as you suspected, so it should be possible to bring out more saturation and differentiation. However, the image was captured under Bortle 6/7 skies, which I think contributed to the weaker star colors. I’ll try some separate, more careful stretching to bring the colors out more effectively.
    [*]
    I hadn’t noticed the extra diffraction spikes at the edges – great catch! I’ll take a closer look at that. I’m using the Starizona coma corrector, so maybe that’s causing the effect. It could be some kind of refraction or internal reflection related to the corrector’s geometry.



Thanks again for your feedback – especially since you phrased it in such an encouraging way. I'm really happy you like the image overall, and I’ll definitely take your suggestions into account for future processing!
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Andreas avatar
Andreas avatar
Noah Tingey:
Looks super cool. The change from revision A to B was a good one. If I had to give one critique, I would say that you could pull more color out of your stars. IC443 has a cool blue and golden color contrast -- I think bringing out the gold and blue stars would complement that well. But overall great photo.



You're absolutely right about the star colors – that's definitely something I still want to improve. The image was taken under Bortle 6/7 skies, which tends to wash out the colors a bit, but I do have plenty of RGB data to work with. I’ll try doing a more careful star stretch and bring out those gold and blue tones to better match the overall color contrast in IC 443 – I completely agree it would make the image pop even more.

Going forward, I’ll make it a point to pay more attention to star color in general – it really adds a lot when done right.

Glad you liked the revision from A to B – it means a lot! 😊
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