One day at a time - Image processing

[Tailspin45]

Several days ago I manage to get almost everything set up right and captured a bunch of images of the Orion Nebula (M42).

I say, "almost everything set up right," because the camera settings I used to capture the images were far from correct. So all the information (photons) I collected was crammed to the left side of a histogram that shows the distribution of pixel intensity. In other words, I had very few details, a bunch of overexposed areas, and almost no solid black in the sky (which I could have prevented with high contrast or light pollution filters).

Thanks to the weather, I've had time to play around with the frames I did get with slowly improving results thanks to a lot of reading and a few nuggets embedded in far too long YouTube videos.

I used SharpCap to capture the images and it does real-time stacking and alignment so you can see what's what and save what's on the screen if you like it. Here, for example, is one image created from six 90-second frames.

After I put the scope away, I tried playing with it using SharpCap's post-processing tools and ruined it

Three days ago I decided to try post-processing in Adobe Lightroom with this ugly result

Yesterday, after some more reading and fiddling, I was able to create something a little nicer

Today I tried using Photoshop and produced this which is slightly better.

So as my title suggests, one day at a time my results are getting better.

The key takeaways are

• You have to start with good subs

• The software you use, like the hardware, makes a big difference in ease of use and results

• Most edits require very small changes

• The real objective is to improve the contrast to reveal very dim details

• Post-processing is an art that requires a lot reading, practice and mistakes, trial and error

• Most video tutorials are far too long and progress far too slowly

• Holding down the ALT key in Lightroom lets you mask highlights

• I need to research available astrophotography add-ons or stand-alone post-processing tools

• The newest addition to the family (rescue dog) will wake up your wife wiggling in delight when you come to bed late after hours of editing

[Ruud]

 
    

[UlteriorModem]

"The sky is not black"...

That is the signature line of one of the Pixinsight Guru's on their forum. It is quite true. If your background is true 'black' you have clipped your image.

[sdbodin]

Just so we are on the same page about 'clipping' the image. I post up this snapshot of an M42 with a histogram superimposed. Note the left side a definite front porch with zero then the peak, the fainter data, then a gradual tail of brighter data.

You still seem to have all the data crammed over to the left and this probably is not due to captured data, only processing. There is an art to this stuff, so don't be discouraged, keep at it.

Good luck,
Steve

[UlteriorModem]

I agree, the first image actually looks like decent data, but the color calibration and stretch are off.

[Tailspin45]

...You still seem to have all the data crammed over to the left and this probably is not due to captured data, only processing.

I agree, the first image actually looks like decent data, but the color calibration and stretch are off.

Here's what I had to work with: 8-bit PNG pre-stretched by SharpCap, which is undoubtedly the source of the problem.

The subs have, if anything, too much room on the left. The seem mottled/noisy, though.

Blank_Skitch_Document.jpg (16 KiB) Viewed 5200 times

I'll re-stack them with Deep Sky Stacker and reprocess them and see if it looks better

[UlteriorModem]

If you would like to share them on drop box or some such let us take a close look at it.

[Tailspin45]

If you would like to share them on drop box or some such let us take a close look at it.

Thank you! They're here.

I played around with them again. Stacked them in Photoshop and also Nebulosity, and tried enhancing each result. It was ugly.

[UlteriorModem]

So those are the individual frames or a stacked version?

[Tailspin45]

So those are the individual frames or a stacked version?

Individual frames, PNGs produced by SharoCap

[Tailspin45]

It also produced this stacked image, which I post here un-post-processed

[SVBONY SV305]
Output Format=FITS files (*.fits)
Colour Space=RGB24
Capture Area=1920x1080
Pan=0
Tilt=0
Black Level=251
USB Speed=1
Frame Rate Limit=Maximum
Gain=6
Exposure=15.000013
Timestamp Frames=Off
White Bal (B)=400
White Bal (G)=242
White Bal (R)=400
Sharpness=100
Saturation=51
Gamma=1.08
Contrast=93
Banding Threshold=35
Banding Suppression=0
Apply Flat=None
Subtract Dark=None
#Black Point
Display Black Point=0.3984375
#MidTone Point
Display MidTone Point=0.697265625
#White Point
Display White Point=0.99609375a
TimeStamp=2020-02-26T05:11:09.4027736Z
SharpCapVersion=3.2.6219.0

[sdbodin]

I took a crack at the data and stacked this with Nebulosity and finished-off in Photoshop CS5. Process was; two star align and stack, auto color balance, digital development to my taste, others will vary, save as .tif and send to Photoshop.

I tried to maintain some sort of dynamic range, but the central region is over exposed. I guess this is with a DSLR? Might help to know the camera and exposures and scope attached. I made no attempt to filter hot pixel only background noise and maintain a decent histogram. The background is quit a bit above black to illustrate that it does not need to be clipped and still be a nice image.

Clear skies,
Steve

[Tailspin45]

Your image sure looks a lot better! I'll try Nebulosity and see if I can at least come close. May have been trying to drag details out that just are';t there.

Scope was Meade 80mm refractor, camera Svbony SV-305 (see above, which I just posted).

[sdbodin]

I would capture in Nebulosity if that camera is supported, but I have no knowledge of this camera or if it could be captured with a pseudonym in Nebulosity, e.g. some other name that is the same animal. So, 15 sec subs, is what I read, really good amount of faint stuff at that short an exposure. But, M42 is maybe the hardest subject to get in all its glory, need really short exposure for the central part and long for the faint outer, then a lot of Photoshop mumbo jumbo to graft all that together.

My shot was 5 sec, 30 sec, 1 min, and 5 min exposures, at least 5 ea. thru my 80 f6.

I think you are getting there, just requires clear skies, and patients, neither of which I have,
Steve

[Tailspin45]

Well, this is better. But you managed to create a nice transition from the grossly blown out core to the "wings." The auto color correction in Nebulousity helped a lot!

So far I have the patience, but not the weather.

Thanks for the pointers and encouragement!

[UlteriorModem]

That an excellent sunset image!

[sdbodin]

Yup a bunch better. Seems that the RGB24 setting in SharpCap is the culprit, this is only an 8 bit depth, 8x3=24. Really need the 16 bits that Nebulosity offers in raw mode. This would get more of the bright stuff before it clips.

Keep at it, a lifetime project,
Steve

[Kanadalainen]

Wow, there is some great advice here. Thanks to Steve and Tom for this mini workshop.

[Tailspin45]

After a few hours more work...

Problem is, I think, the underlying sub-images really aren't helping. But at least this isn't embarrassing, like my earlier attempts.

The bigger problem is I couldn't possibly explain what I did differently. A little of this, a little of that, etc, etc, etc.

Started with a new program called Observatory by Code Obsession that let me sort through all 941 subs, align and stack the ones I liked. Then Lightroom for all the tweaks.

[UlteriorModem]

I probably overlooked it but... why are you using sharpcap?