I'm not an expert but I'm happy to critique. However, images uploaded to IIS are squeezed down to < 200kB, a lot of artefacts created, and this will make it hard to identify any issues with processing.
Can I suggest possibly uploading to astrobin. They accept image files up to 25MB on a free account, and you can provide a link. Then we can see your image in all its glory.
The image is SiiGOiii
2min Subs
x40 Ha (used for luminance)
x30 Sii
x15 Green
X30 Oiii
WO GT-81 & ASI2600MM
Losmandy G-11
I'm not too sure about my adjustment of the field flatterner, it always seems to be a compromise and trying to squeeze two nebula in seems to led to something a bit worse than one nebula in the middle.
I'm still battling with the mount (second hand). I'm not sure I have confidence yet that everything is working well. I recently dropped from 5min subs to 2min hoping to get perfectly round stars but I think there are still issues.
I think the image has potential, but there are a couple of things you can focus on to improve.
For me, the first thing I see is noise. More subs would help. I ran some noise reduction (NoiseXterminator) on a portion of your image to clean it up and I've attached the results below. I think it helps.
In the noise reduced image you'll also see "ringing" around the stars. Is that from star reduction, deconvolution, some form of masking during processing, do you know when it's occurring?
Also, if you want to check your field flatness, I can help. If you can post up a single unprocessed sub from the image onto your google drive I'll run it through CCDInspector.
First of all I want to say well done on a very nicely captured and processed image. There is a lot of detail and some very nice colours.
From a personal viewpoint, I would decrease saturation a little. That is personal taste though. Others love saturation. Also, I would recommend looking a little further at your image acquisition. There seems to be some star elongation, perhaps due to tilt, guiding, polar alignement,... However, I am being super picky because of your request. Overall this is an image you should be very proud of. Well done indeed.
This region of the sky has many delightful natural colours, so I'd question:
Why narrow band?
But if NB floats 'yer boat, I'd suggest choosing a palette to reveals the underlying physical processes, rather than 60's pop art that seems to be a bit of a trend of late.
Still hard to critique your technique at the posted scale, but if you ensure the stars don't have weird shapes, multi-coloured fringes or dark doughnuts
the rest should fall into place nicely.
Hi Chris.
I did some star reduction and deconvolution in the processing. That stuff always seems a like a trade off with ringing and greying out around the stars.
Thanks for the comments
Quote:
Originally Posted by ChrisD
Hi John,
I think the image has potential, but there are a couple of things you can focus on to improve.
For me, the first thing I see is noise. More subs would help. I ran some noise reduction (NoiseXterminator) on a portion of your image to clean it up and I've attached the results below. I think it helps.
In the noise reduced image you'll also see "ringing" around the stars. Is that from star reduction, deconvolution, some form of masking during processing, do you know when it's occurring?
This region of the sky has many delightful natural colours, so I'd question:
Why narrow band?
But if NB floats 'yer boat, I'd suggest choosing a palette to reveals the underlying physical processes, rather than 60's pop art that seems to be a bit of a trend of late.
Still hard to critique your technique at the posted scale, but if you ensure the stars don't have weird shapes, multi-coloured fringes or dark doughnuts
the rest should fall into place nicely.
Thanks for your thoughts Peter. As far as colors go I was actually trying to put Green in to get away from the SHO pallet. What comes out is a bit pastel-ly for my tastes really but SHO looks too blue and brown.
First of all I want to say well done on a very nicely captured and processed image. There is a lot of detail and some very nice colours.
From a personal viewpoint, I would decrease saturation a little. That is personal taste though. Others love saturation. Also, I would recommend looking a little further at your image acquisition. There seems to be some star elongation, perhaps due to tilt, guiding, polar alignement,... However, I am being super picky because of your request. Overall this is an image you should be very proud of. Well done indeed.
Regards,
Stéphane
Thanks, yes I think tracking needs to improve esp for 2min subs
This region of the sky has many delightful natural colours, so I'd question:
Why narrow band?
But if NB floats 'yer boat, I'd suggest choosing a palette to reveals the underlying physical processes, rather than 60's pop art that seems to be a bit of a trend of late.
Still hard to critique your technique at the posted scale, but if you ensure the stars don't have weird shapes, multi-coloured fringes or dark doughnuts
the rest should fall into place nicely.
Completely agree!!
Quote:
Originally Posted by Gastraea
Thanks for your thoughts Peter. As far as colors go I was actually trying to put Green in to get away from the SHO pallet. What comes out is a bit pastel-ly for my tastes really but SHO looks too blue and brown.
John, I'm confused about what you've done. In the SHO palette, HII emission would show up as green. So, if anything, a raw SHO image of this neb, where HII dominates, would require you to colour rebalance quite a bit to REMOVE some green. Moreover, I have no idea why green would be absent in the first place to the extent you'd need to "put green in" . Note also that putting green in will move you towards, not away, from an SHO image.
PS: Ah! OK, I see you've used the green filter, not Ha so your image is HaSGO. That explains a lot. You can't just put Ha in as a luminance channel without having Ha colour to hang off it. Won't work. You should start with Ha in the green channel and use LHa as luminance.
John, I'm confused about what you've done. In the SHO palette, HII emission would show up as green. So, if anything, a raw SHO image of this neb, where HII dominates, would require you to colour rebalance quite a bit to REMOVE some green. Moreover, I have no idea why green would be absent in the first place to the extent you'd need to "put green in" . Note also that putting green in will move you towards, not away, from an SHO image.
PS: Ah! OK, I see you've used the green filter, not Ha so your image is HaSGO. That explains a lot. You can't just put Ha in as a luminance channel without having Ha colour to hang off it. Won't work. You should start with Ha in the green channel and use LHa as luminance.
Hi Thanks for your comments. I can see I'm going to have to give the RGB pallet another go.
So I can tell you my process and see if it make sense.
(this is in pixinsight)
After BG removal & stretch I combine SiiGOiii to make RBG.
I remove any greencast with SCNR
I then use a Ha in LRGB combination with Ha as L.
(I'm adapting my another workflow and have just realized I could have done LRGB directly but nevermind)
So this was an experiment to see what happened. I adapted it from this video https://youtu.be/o4Rl3heOIro from Dylan O'Donnell where he uses a HaGOiii pallet as a compromise between narrowband with it's psychedelic colours and RBG.
Anyway I guess the suggestion is that I might like to try HaRGB, is this correct?
In reality I only have access to my Bortle 4 skies in my backyard so initially I jumped on the narrowband bandwagon.
Hi Thanks for your comments. I can see I'm going to have to give the RGB pallet another go.
So I can tell you my process and see if it make sense.
(this is in pixinsight)
After BG removal & stretch I combine SiiGOiii to make RBG.
I remove any greencast with SCNR
I then use a Ha in LRGB combination with Ha as L.
(I'm adapting my another workflow and have just realized I could have done LRGB directly but nevermind)
I don't use Pixinsight and I'm not a fan of NB. I prefer the beauty of a natural palette. However, I do appreciate an SHO image if it's done correctly and the colours are rich and well balanced to reveal underlying processes.
Quote:
Originally Posted by Gastraea
So this was an experiment to see what happened. I adapted it from this video https://youtu.be/o4Rl3heOIro from Dylan O'Donnell where he uses a HaGOiii pallet as a compromise between narrowband with it's psychedelic colours and RBG.
Just a note, NB colours don't need to be psychedelic.
Quote:
Originally Posted by Gastraea
Anyway I guess the suggestion is that I might like to try HaRGB, is this correct?
In reality I only have access to my Bortle 4 skies in my backyard so initially I jumped on the narrowband bandwagon.
Do you have a luminance filter? My advice would be to try either LRGB, RGB or straight SHO first. If you want an enhanced natural palette image, do LHa(RHa)G(BHa) (cf: my version from 2009 - Bortle 4 skies at the time)
PS: If you know there's some Oiii signal present, you can also augment the blue and green channels with some Oiii data to taste; usually 20% and 10% respectively. I call that augmented natural palette.
Last edited by marc4darkskies; 28-07-2022 at 08:10 AM.
Reason: Description of augmented natural palette blend
Hi Chris.
I did some star reduction and deconvolution in the processing. That stuff always seems a like a trade off with ringing and greying out around the stars.
Very true. Personally I avoid deconvolution because it can causes more problems in the image than it fixes. Sometimes I use it on galaxy images but generally not for nebula. Just a personal choice.
Very true. Personally I avoid deconvolution because it can causes more problems in the image than it fixes. Sometimes I use it on galaxy images but generally not for nebula. Just a personal choice.
Chris
Thanks Chris
I have been following some youtube tutorials on pixinsight and at least in the first instance it's all monkey see monkey do. There were great to start with but when you look closely and start to get fussy you start to wonder about certain things. The greying around stars also seems to look green when contrasted against the often red magenta in the nebula. Anyway good to see others have different opinions about how to process this stuff.
As far as CCDInspector goes I set up the optics train a while ago during my 30day evaluation of the software and haven't disassembled it since. Cross fingers it's still about the same. I just wish that software wasn't such poor value for money. I'm not happy enough with the subs with this image to bother giving it to you. I'll try to tackle the tracking next. The stars aren't too bad but there is room for improvement. Perhaps I should ask Mr Ward how much a AP MACH2GTO is going for nowadays (one day perharps )
Last edited by Gastraea; 27-07-2022 at 06:08 PM.
Reason: typo
. Note also that putting green in will move you towards, not away, from an SHO image.
(one day perharps 
)
