[RCC] NGC 7380 Wizard Nebula (Ha/OIII)

Request for feedback
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[deleted]
[deleted]
Hello Folks,

I need some general guidance for image processing in Siril, I'm fooling around with the Askar C1 (Ha/OIII) filter on my OSC for this image of NGC 7380. I plan on imaging the nebula with the C2 (SII/OIII) filter in the next night of two and combine them for a SHO image..

Part of my problem is that I'm really new to this aspect of the image processing, another problem is that I have a Red/Green color deficiency, according to the test that I've taken online, I have a moderate deficiency in the red color.. So subtle hue changes in red may not register..

With that being said here is the work flow that I used:

Stacking: Siril OSC_Preprocessing script

Image Processing: Siril
1) Auto Strech view
2) Image Processing => Background Extraction
3) Image Processing => Color Calibration = Photometric
4) Linear view
5) Image Processing => Histogram Transformation => Auto stretch
6) Image Processing => Remove Green Noise
7) Image Processing => Histogram Transformation => Auto stretch
8) Save => JPG File

The attached image is from two night sessions,
session1: 46x 180sec, 2.3hrs
session2: 40x 180sec, 2.0hrs

I'm debating on weather to take some more Ha/OIII data tonight, or switch to the C2 filter and start collecting SII/OIII data now, merge my data for the SHO image and resubmit my RCC on the final image...

NGC7380: NGC7380

Thanks
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Tony Gondola avatar
Tony Gondola avatar
I think there's a lot in there but the stars are just taking over the image. You would really benefit by removing the stars and processing them separately.
Brian Puhl avatar
Brian Puhl avatar
So first off, you've got some things going on with stars there.   I cant quite put my finger on it because they're quite bright, but it looks like you have tilt in your optical train, the bottom left is far worse than the top.    Smaller sensors like the 533 usually don't display tilt errors much since they're so small, so that tells me this is pretty far out of whack.  I would do yourself a favor and work on getting your optics aligned, and possibly backfocus dialed in properly before you spend too much time here.

As for the processing, you're using a unique filter in which I don't really have experience with, but since it's considered a dual narrow(ish)band filter, I'd extract the red and green channels and use them as narrowband, process them as such.   I would not use any sort of color calibration here because the image is not true color.    Regardless of approach taken, the image is also extremely noisy.   Noise is lack of signal…. so naturally if we don't have enough signal, we should not try to stretch our image as hard.   Try relaxing your stretch by at least a factor of two.  You'll find the results are much more appealing.
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[deleted]
[deleted]
Brian Puhl:
So first off, you've got some things going on with stars there.   I cant quite put my finger on it because they're quite bright, but it looks like you have tilt in your optical train, the bottom left is far worse than the top.    Smaller sensors like the 533 usually don't display tilt errors much since they're so small, so that tells me this is pretty far out of whack.  I would do yourself a favor and work on getting your optics aligned, and possibly backfocus dialed in properly before you spend too much time here.

As for the processing, you're using a unique filter in which I don't really have experience with, but since it's considered a dual narrow(ish)band filter, I'd extract the red and green channels and use them as narrowband, process them as such.   I would not use any sort of color calibration here because the image is not true color.    Regardless of approach taken, the image is also extremely noisy.   Noise is lack of signal.... so naturally if we don't have enough signal, we should not try to stretch our image as hard.   Try relaxing your stretch by at least a factor of two.  You'll find the results are much more appealing.

Thanks Brian, A question.... would flexure be considered the same as tilt?
Tim Stevenson avatar
Tim Stevenson avatar
I exclusively use a DB filter… in my case I have used the L-eNhance, L-Extreme, and L-Ultimate.

My flow is…
Crop to remove any artifacts around the edges
ImageSolver to get the coordinates associated with the image
SpectroPhotometricColorCalibration to correct the star color which will also correct the nebula color
BlurXTerminator
NoiseXTerminator
HistrogramTransformation … a mild amount to the point where you just start seeing the nebula
ArcsinhStretch … be careful not to over stretch it.  That's my biggest problem and it's impossible to correct later.  I'm actually reprocessing images that I now feel are over stretched.
StarXTerminator
Sharpen the image … I use wavelets to sharpen and have good success IMO
NarrowbandNormalization … I just learned about this process and I love it.  It really helps to bring out the OIII signal and get the colors you want … HOO, SHO, etc
Last items are tweaks to contrast … saturation … brightness

Oh … your stars.  I agree, they look a little off.  But you can reduce them in your stars only image before you recombine.

I hope this helps.
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Brian Puhl avatar
Brian Puhl avatar
Brian Puhl:
So first off, you've got some things going on with stars there.   I cant quite put my finger on it because they're quite bright, but it looks like you have tilt in your optical train, the bottom left is far worse than the top.    Smaller sensors like the 533 usually don't display tilt errors much since they're so small, so that tells me this is pretty far out of whack.  I would do yourself a favor and work on getting your optics aligned, and possibly backfocus dialed in properly before you spend too much time here.

As for the processing, you're using a unique filter in which I don't really have experience with, but since it's considered a dual narrow(ish)band filter, I'd extract the red and green channels and use them as narrowband, process them as such.   I would not use any sort of color calibration here because the image is not true color.    Regardless of approach taken, the image is also extremely noisy.   Noise is lack of signal.... so naturally if we don't have enough signal, we should not try to stretch our image as hard.   Try relaxing your stretch by at least a factor of two.  You'll find the results are much more appealing.

Thanks Brian, A question.... would flexure be considered the same as tilt?



Flexure is when the guide scope and the imaging scope become misaligned due to temperature differences or other factors causing the mounting plate and rings to warp or bend.   It will happen slowly over time and cause oval stars in your subs, but the oval stars will be consistent throughout the entire image.   In your case, it's mostly bottom left, so flexure is not a factor here.
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[deleted]
[deleted]
@Brian Puhl  Thanks again... I'll recheck the back focus spacing on the optical train.....  When I take a more critical look at the image, I want to say the the stars seem "bloated" and not more pinpoint could that be what you and @TStevens83 see as something being off?

Thanks again, I do appreceate the feed back from everyone!!
Tim Stevenson avatar
Tim Stevenson avatar
[deleted] ​​​​@Brian Puhl ... I agree with you Phil that the stars seem VERY bloated.  How did you focus the image?  For comparison, my stars are much smaller than yours and my image is at more magnification.   

https://www.astrobin.com/wmy85x/

Note that I probably did do some star reduction in this image and it was before I learned about NarrowbandNormalization so it's on my list to redo.
[deleted]
[deleted]
[deleted] ​​​​@Brian Puhl ... I agree with you Phil that the stars seem VERY bloated.  How did you focus the image?  For comparison, my stars are much smaller than yours and my image is at more magnification.   

https://www.astrobin.com/wmy85x/

Note that I probably did do some star reduction in this image and it was before I learned about NarrowbandNormalization so it's on my list to redo.

So this is my pre-imaging routine, which is all done thru my ASIair:

1) Perform PA
2) Perform AF, Check AF results with Bahtinov mask, and adjust if needed manually
3) Select / slew to taget to be imaged
4) Startup / calibrate guiding
5) Perform another AF on target, Check AF results with Bahtinov mask, and adjust if needed manually
6) Put in my autorun
7) Go

Now, with what you and @Brian Puhl have commneted on the stars.. I probably should add, I pulled apart my optical train to clean out some dust particales I was seeing... obviously pulling it apart and putting it back together means the orientation of the camera sensor may not be exactly lined up from the previous nights session....

Using the previous nights image I slew to target, but the image framing was off by about 0.6 deg, I went ahead and synched it up and proceeded with imaging, I'm taking a guess, could that be one of the things wrong with the image? I kept each nights image session in theri own folder, but when I went to stack them, I just dumped them all in the Siril Home/Lights folder and proceeded with the stacking... I made the asumption that if there were any problems between the two session images, Siril would choke, give me an error and stop processing

Forgot to mention, I'll be making a slow transition to N.I.N.A as soon as I get comfortable with using that software
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Brian Puhl avatar
Brian Puhl avatar
Frame rotation would not affect the stars.  The only place you would notice rotation would be the edges of the frame where stacking edges appear.

What I was talking about was physical tilt of the sensor.  One side of the sensor is closer to the corrector than the other, which basically means one side is slightly out of focus and will lead to the oblong stars.   Tilt is a pita to deal with when you're new, but you can get tilt plates which are lifesavers.  

Try opening a single sub, debayered and run scripts>abberation inspector on it.  Post a screenshot in here.
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Tim Stevenson avatar
Tim Stevenson avatar
[deleted] ​​​​@Brian Puhl  ... Phil, I have a Skywatcher Quattro 250P and I haven't cleaned the mirror in a couple years.  I trust that the flats will take care of any dust bunnies.

I would recommend looking at the two sessions of subs using the Blink process in PI.  I don't use Siril, I use AstroPixelProcessor and APP wants you to enter and identify your subs from separate sessions.  I do not know how Siril handles different sessions.

Does ASIair have an automatic focus routine?  I use NINA and I trust it's AF routine to give me the best focus possible.  BTW ... I love NINA.
[deleted]
[deleted]
@Brian Puhl , @TStevens83 .... Gents, I think the back focus may be out of adjustment... I'm not sure... When I look at the final stacked image from my first night at 400x, On the bigger stars I'm seeing spikes, and I see the same on my session 2, and session 1&2 togetther stacked images per the following image of my session 1 stacked image, I'm going to recheck the back focus spacing for the 73A field flattener... it's adjustable.. so in my dinking around, and taking the image train apart it's probably that it losened up and changed.

@TStevens83 Yes, the ASIair has a auto focus program in it, so that's what I've been using.. along with the ASIair to get my feet wet with the imaging process, I won't say I completely understand of everything that is going on, but at least I now have a better understanding now to where I can start to play around with nina and phd2

Thanks for your time and feed back, much appreciated

[deleted]
[deleted]
I exclusively use a DB filter... in my case I have used the L-eNhance, L-Extreme, and L-Ultimate.

My flow is...
Crop to remove any artifacts around the edges
ImageSolver to get the coordinates associated with the image
SpectroPhotometricColorCalibration to correct the star color which will also correct the nebula color
BlurXTerminator
NoiseXTerminator
HistrogramTransformation ... a mild amount to the point where you just start seeing the nebula
ArcsinhStretch ... be careful not to over stretch it.  That's my biggest problem and it's impossible to correct later.  I'm actually reprocessing images that I now feel are over stretched.
StarXTerminator
Sharpen the image ... I use wavelets to sharpen and have good success IMO
NarrowbandNormalization ... I just learned about this process and I love it.  It really helps to bring out the OIII signal and get the colors you want ... HOO, SHO, etc
Last items are tweaks to contrast ... saturation ... brightness

Oh ... your stars.  I agree, they look a little off.  But you can reduce them in your stars only image before you recombine.

I hope this helps.

Hey Tim, thanks for your work flow... I'm definetly going to look at all of the processing programs that you're using in your process...

I measured all of my back spacing between the 73A flattener and the imaging sensor, and I was off about 0.8mm out, if I were to believe the markings on the 73A flattener

Anyway... I got everything setup last night and took 30x 180sec frames, I didn't see alot of change in the star size in the stacked fit file, so I'll be at it again tonight, make a 5mm adjustment to the flattener and hopefully see some sort of change in the image in one direction or another (Better or worse), so i can have a reference point on which to work from.

Another question I have, when I zoom in to check the stars in the corners.. should i look at the individual light frames or at the stacked image file??

thanks
Tim Stevenson avatar
Tim Stevenson avatar
Hi Phil, you have to use single subs to evaluate your optical train… stacking most likely would mask any issues you want to evaluate
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Robert Habolin avatar
Robert Habolin avatar
First off, not a bad image for a beginner. However, this is a TOUGH target. It's much dimmer than other nebulas and requires lots and lots of exposure. So get att least 10 hours before you even start to process. ( trust me its worth it, it makes processing easier too ) 

Then get pixinsight, and Starexterminator from Russel Croman. its worth every penny... Because you will need to remove those stars to really access all the nebulosity thats underneath. 

My workflow for something like this goes roughly : Pixinsight, DBE for all filters. Combine RGB, noise red, Star separation save as sep files. Same for Luminance. Same for Narrowband filters. Histogram Transform to sort of halfway of what would be final stretch. BlurX, and another noise red. Then into Photoshop, with RGB STARLESS, RGB STARS. LUM STARLESS, LUM STARS, HA STARLESS, ( we dont need the HA STARS. ) In photoshop all the levels, selective colors, contrast enhancements, combination of channels. ( this includes elaborating with how much of the narrowband signal i want blended or vice versa ) adding the starlayers ( this usually is mostly RGB stars with a little bit of the LUM stars added depending of how much i want) , tweaks in Camera raw filter. Then back to pix for another round of BlurX if needed ( often mostly for starsizes ) and a gazillion of other small edits thats too much to mention, but in a nutshell. 

But as first step, for you id really try and separate the stars, so you can see what's underneath, and also get more hours of data. 

here's an image of this target that i revisited today for some new editing. https://www.astrobin.com/full/393468/B/ 

its with much longer Focal length obviously so much more zoomed in, but this is 30 hours of exposure.
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[deleted]
[deleted]
@Robert Habolin Thanks for your comments and insight..... I've started to think about the quality of what I want to do with my astrophotography hobby. I recently watched a Youtube vid where the individual talked about Slowing down and spending more time on the target to improve the image quality.

I'm assuming everyone here started like I am, I stacked and processed my first image and "wow" that looks really cool, not great... "Cool" and I'm off posting to my Facebook... Since joining this site... I've looked at other individuals work... compared it to some of what I did and thought "Man, I got a lot of work to do" So now I'm making the shift of quantity, to quality Spending more time on gathering data on a Project... and with multiple rigs I can set one up for that, while another can allow me to hop around the sky looking for other possible projects

I've been thinking about jumping to PixInsight, the cost of the software has me hesitant on pulling the trigger on that.. but in all likelihood I'll go ahead to do so soon... it's kind of funny that I had no problem on spending $320 bucks on a pieces of glass, but I'm hymming and hawing on a pieces of software that will probably help my final images , Thanks again, and sorry for the long winded babble
Robert Habolin avatar
Robert Habolin avatar
I heard someone say, Astrophotography is a black hole that sucks you in deeper and deeper, forever chasing a better and better picture. It's very true, but we all HAVE to start somewhere. And this is a great start. 

As far as spending money on gear, apps. I def hear ya. But, if I was to choose one thing it would be Pixinsight, as so many use it, there are tons of tutorials. And you can do so much with it. If you want to get decent images, Pix is almost a necessity. 

Feel free to hit me up with any questions regarding processing. Always happy to help, if i can. 


cheers 
Rob
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Tim Stevenson avatar
Tim Stevenson avatar
I agree Rob … PixInsight is a must… IMO.  We all started in humble beginnings and most of us are still learning.  I'm willing to help at any time.

Tim