astro pixel processor

[Rowland]

Hi Michele. My interest was comparing results to see what APP is doing, rather than critiquing your work...

PixInsight manages flat illumination really well. My script produced virtually the same result as APP and I need to work on improving flat correction in the script.

Thanks again for sharing your work. Nice image set. No big deal about the flats. Difficult to get right at anytime.

Having tried just about everything to take good flats, I finished up buying a custom made lightbox. The user (me) is still the main source of error.

Clear skies...

Rowland
EDIT: Here is a work flow that eliminated the gradients almost entirely. I'm sure the process beyond Wipe could be improved. First, the stacked image was separated into L R G B channels and recombined in ST LRGB and pushed the colour channel blur to 5 pixels. Binned to 50% which helps as well.

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-----------------------------------------------------------
StarTools 1.4.329
Sun Oct 22 11:38:24 2017
-----------------------------------------------------------
File loaded in LRGB module [/home/geoland/Astrophotography/Veil/L.tiff].
File loaded in LRGB module [/home/geoland/Astrophotography/Veil/R.tiff].
File loaded in LRGB module [/home/geoland/Astrophotography/Veil/G.tiff].
File loaded in LRGB module [/home/geoland/Astrophotography/Veil/B.tiff].
--- LRGB
Parameter [Cap Green] set to [No]
Parameter [Channel Interpolation] set to [On]
Parameter [RGB Blur] set to [5.0 pixels]
Parameter [Blue Ratio] set to [1.00]
Parameter [Green File] set to [1.00]
Parameter [Red Ratio] set to [1.00]
--- Bin
Parameter [Scale] set to [(scale/noise reduction 50.00%)/(400.00%)/(+2.00 bits)]
--- Auto Develop
Parameter [Ignore Fine Detail <] set to [Off]
Parameter [Outside ROI Influence] set to [15 %]
--- Wipe
Parameter [Mode] set to [Correct Color & Brightness]
Parameter [UNKNOWN] set to [Yes]
Parameter [Precision] set to [256 x 256 pixels]
Parameter [Dark Anomaly Filter] set to [2 pixels]
Parameter [Drop Off Point] set to [0 %]
Parameter [Corner Aggressiveness] set to [100 %]
Parameter [Aggressiveness] set to [75 %]
--- Auto Develop
Parameter [Ignore Fine Detail <] set to [Off]
Parameter [Outside ROI Influence] set to [15 %]
--- HDR
Parameter [Small Detail Precision] set to [Max]
Parameter [Channels] set to [Brightness Only]
Parameter [Algorithm] set to [Reveal All]
Parameter [Dark/Bright Response] set to [1.00]
Parameter [Detail Size Range] set to [20 pixels]
Parameter [Strength] set to [1.2]
--- Color
Parameter [Cap Green] set to [To Yellow]
Parameter [Bias Slider Mode] set to [Sliders Reduce Color Bias]
Parameter [Style] set to [Scientific (Color Constancy)]
Parameter [LRGB Method Emulation] set to [RGB Ratio, CIELab Luminance Retention]
Parameter [Dark Saturation] set to [2.00]
Parameter [Bright Saturation] set to [Full]
Parameter [Saturation Amount] set to [200 %]
Parameter [Blue Bias Reduce] set to [1.00]
Parameter [Green Bias Reduce] set to [1.22]
Parameter [Red Bias Reduce] set to [1.83]
Parameter [Mask Fuzz] set to [1.0 pixels]
--- Wavelet Sharpen
Parameter [Intelligent Enhance] set to [Yes]
Parameter [Scale 1] set to [100 %]
Parameter [Scale 2] set to [100 %]
Parameter [Scale 3] set to [100 %]
Parameter [Scale 4] set to [100 %]
Parameter [Scale 5] set to [100 %]
Parameter [Mask Fuzz] set to [8.0 pixels]
Parameter [Amount] set to [60 %]
Parameter [Small Detail Bias] set to [75 %]
--- Wavelet De-Noise
Parameter [Scale 1] set to [90 %]
Parameter [Scale 2] set to [90 %]
Parameter [Scale 3] set to [90 %]
Parameter [Scale 4] set to [90 %]
Parameter [Scale 5] set to [0 %]
Parameter [Mask Fuzz] set to [1.0 pixels]
Parameter [Scale Correlation] set to [6]
Parameter [Color Detail Loss] set to [12 %]
Parameter [Brightness Detail Loss] set to [12 %]
Parameter [Grain Size] set to [7.0 pixels]
Parameter [Read Noise Compensation] set to [Off]
Parameter [Smoothness] set to [75 %]
--- 
Parameter [Quality] set to [Medium]
Parameter [New Darker Than Old] set to [Yes]
Parameter [Grow Mask] set to [0 pixels]
Parameter [Neighbourhood Samples] set to [0]
Parameter [New Must Be Darker Than] set to [Off]
Parameter [Neighbourhood Area] set to [200 pixels]
--- 
Parameter [Quality] set to [Medium]
Parameter [New Darker Than Old] set to [Yes]
Parameter [Grow Mask] set to [0 pixels]
Parameter [Neighbourhood Samples] set to [0]
Parameter [New Must Be Darker Than] set to [Off]
Parameter [Neighbourhood Area] set to [200 pixels]
File saved [/home/geoland/Astrophotography/Veil/stack_Veilst.tif].

[micheleorsini]

Hi Rowland,
don't worry, I appreciate any comment that might lead to a better practice!

Flats are my current weak point, I still have problems: my last picture (soon will be on Gallery) showed a checkered pattern (with dithering, this time I'm sure!) and after making different stacking tests I found that the fault was in flats. I suspect they were underexposed, because my DIY flatbox is crappy and stretching them lead to the same checkered pattern you have in lights.

In that case I ended up not using them, I've been lucky because the imaging train with WO Star71 shows no vignetting and the cleanup sensor routine of my Canon works amazingly well - at least, at the level I need, I saw dust motes "fingerprints" in lights literally disappearing after using it - but I'm aware of the fact that this is one of the things to fix sooner.

"Inspired" by your idea of splitting LRGB, I was looking for a method to build a Luminance layer and I ended up in User Notes for Layer module. Here I found yet another post processing technique (http://forum.startools.org/viewtopic.php?f=12&t=1149, see Splitting into Luminance and RGB before Processing): I will repeat both yours workflow and the one described there the see what happens!!

thank you again!!

Michele

[Rowland]

If you have ImageMagick installed, you can extract the RGB channels from your stacked image like so - on the command line. I could write a small utility to do this, if it were useful for Linux/Mac - very quick.

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convert stack.tiff -depth 16 -separate +channel %d.tiff

...which produces 0.tiff 1.tiff 2.tiff or R G B, in that order. Rename 0.tiff to R.tiff and so on.

Next, extract the luminance channel from your stacked image

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convert stack.tiff -depth 16 -alpha off -colorspace Gray L.tiff

Change tiff to whichever format you are using - fits png.

If you want luminance and lightness for a comparison or mask...

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convert stack.tiff \( -clone 0 -depth 16 -colorspace LAB -separate -channel L +write Lab.tiff +delete \) \ -depth 16 -alpha off -colorspace Gray L.tiff

-depth 16 is nominal and optional. I use 16 bit because it's adequate and fast.

[micheleorsini]

I know very little about ImageMagick, but yes, it is installed

Thank again Rowland!!

M.

[Rkonrad]

Hi Michele,

Thanks for your data. Sorry I can't contribute to the core of your questions but I downloaded your final stacked image and had a lot of fun. Great data! Would you mind sharing what scope do you use? (hopefully upgrading at some point soon from a cheapish zoom lens). I didn't have any issues removing odd gradients at all. Is that stacked with dss or app? The upper right corner is rather dark but maybe that's the way its supposed to be? My result is a private picture on flickr. https://www.flickr.com/gp/rkonrad/6G280F
Cheers Richard

[Rkonrad]

Hi Rowland,

Just reading your tips on separating channels. I was wondering what would be the advantage to this? Does it improve colour accuracy? Thanks.

Richard

[Rowland]

Hi Richard.

Depending on the data, separating the stacked RGB and recombining in the LRGB module, produces an image with much more control over colour saturation.

An added benefit appears to be the ability to blur the RGB colour channels reducing colour noise. But I find that combining channels promotes this as well.

With Michele's data, the LRGB process eradicated the gradients she reported in the RGB. But I did include a 50% bin.

Your rendition of the Veil is very nice and you should post the processing log. I spend more time developing preprocessing methods than I do post processing - not my strong suit.

Edit: as to accuracy, I find some variation with Red tending to pink. This may not be to everyone's liking. Primarily, the object was to improve the Wipe result. I applied the default scientific RGB luminance ratio palette.

[Rkonrad]

Thank you Rowland. I shall try that soon - and thanks for the methodology.

Richard

[micheleorsini]

Richard thank you
your post processing is really good, I'm quite impressed because to have such faint details I had to mix RGB with HA

I'm sorry I have to try everything by myself, had to reinstall everything for work in the last two days, I'll try in a few days

btw, this thread is a goldmine, thank you all dudes!

Michele

p.s. I'm Michele (italian for Michael or Mike), a male name, not an important thing anyway

[micheleorsini]

p.p.s. Richard can you provide the startools log? I'm curious!