Heart and Soul processing question.

[Adreneline]

Thanks vlaiv. I'll give it a go - nothing fancy though!

Adrian

 

[Adreneline]

Well @vlaiv I've given it a go and the result is not great as the OIII has pretty much disappeared again despite massive stretching of the starless image. At least I have practised the method!

I just need to grab several more hours of OIII on a clear moonless night. Simple!

Thanks for all your help.

Adrian

[Gina]

A clear moonless night is what I need too!! 

Edited March 6, 2020 by Gina

[jager945]

If Ha and OIII are weighted properly to make a synthetic luminance frame, you have some pretty decent signal (your calibration is quite excellent!).

If your software does not have an automatic weighting feature when compositing your synthetic luminance, then it is important to remember that, if you are weighting stacks made up of sub frames of equal exposure times, however with different numbers of subs, then relative signal quality in these individual stacks only increases with the square root of the amount of exposures.

E.g. if you have twice as many Ha sub frames as O-III frames, then signal in the Ha stack is sqrt(2) ~ 1.4x better (not 2x!).

As the human eye is extremely forgiving when it comes to noise in colour data, you don't need too much signal if your calibration is otherwise very good to augment your (deep) luminance rendition with O-III colouring. Creating, for example, a typical HOO bi-color then becomes fairly trivial (as usual, however, stars are pretty dominant in the O-III band however);

Hope this helps!

 

 

 

[Adreneline]

1 hour ago, jager945 said:

If Ha and OIII are weighted properly to make a synthetic luminance frame, you have some pretty decent signal (your calibration is quite excellent!).

Thank you! I’m assuming you used the .fit files I posted to achieve the image in your post. Is your image a straight HOO or is it a luminance augmented HOO? - sorry I’m a little confused. How did you create the synthetic luminance image?

Thanks again for your help and sorry if I’m missing something obvious.

Adrian

 

[jager945]

2 hours ago, Adreneline said:

Thank you! I’m assuming you used the .fit files I posted to achieve the image in your post. Is your image a straight HOO or is it a luminance augmented HOO? - sorry I’m a little confused. How did you create the synthetic luminance image?

Thanks again for your help and sorry if I’m missing something obvious.

Adrian

 

Apologies for any confusion Adrian! The two datasets were used by StarTools to automatically;

• Create a synthetic luminance master (e.g. making the proper blend of 920s of O-III + and 2280s of Ha). You just tell ST the exposure times and it figures it out, but it in this instance, it would have calculated a signal precision of 1.77:1 (Ha:O-III), derived from sqrt(2880/920) for Ha vs sqrt(920/920). So I believe that would have yielded a 1/(1+1.77) * 100% = ~36% OIII vs 1.77/(1+1.77) * 100% = ~64% Ha blend.
• Create a synthetic chrominance master at the same time (e.g. mapping Ha to red, O-III to green and also blue)

If you are using PS or PI, then you can stop reading here as the following will not be possible (you will want to process both datasets with separate workflows and then afterwards combine chrominance and luminance into one image to the best of your abilities).

In ST, the engine processes both synthetic luminance and chrominance masters simultaneously yet separately (for example, during gradient removal both datasets are treated at once). Most operations only affect the luminance portion (stretching, wavelet sharpening, decon, etc.) until you do final color calibration towards the end (please don't do color calibration this late in PS or PI though!) of your processing flow, which will seamlessly merge color and luminance. During this step, you can boost the color contribution of any channel (or remap channels at will), completely separate to the brightness and detail you brought out. It's one work flow, one integrated process with full control over luminance and chrominance interplay of the final result.

If interested, this was the entire work flow for that image in ST 1.6;

--- Compose

Load Ha as red, O-III as green and O-III - again - as blue
Parameter [Luminance, Color] set to [L + Synthetic L From RGB, RGB]
Parameter [Blue Total Exposure] set to [Not set] (we only want to count O-III's contribution once)
Parameter [Green Total Exposure] set to [0h16m (16m) (960s)]
Parameter [Red Total Exposure] set to [0h37m (37m) (2220s)] (exposure times have to be multiples of 60s; close enough )
--- Bin
Parameter [Scale] set to [(scale/noise reduction 35.38%)/(798.89%)/(+3.00 bits)]
Image size is 1663 x 1256
--- Crop
Parameter [X1] set to [78 pixels]
Parameter [Y1] set to [24 pixels]
Parameter [X2] set to [1613 pixels (-50)]
Parameter [Y2] set to [1203 pixels (-53)]
Image size is 1535 x 1179
--- Wipe

Will remove gradients and vignetting in both synthetic datasets (Use Color button to toggle between datasets).
Parameter [Dark Anomaly Filter] set to [6 pixels]
Parameter [Drop Off Point] set to [0 %]
Parameter [Corner Aggressiveness] set to [95 %]
--- Auto Develop
Parameter [Ignore Fine Detail <] set to [3.0 pixels]
Parameter [RoI X1] set to [466 pixels]
Parameter [RoI Y1] set to [60 pixels]
Parameter [RoI X2] set to [779 pixels (-756)]
Parameter [RoI Y2] set to [472 pixels (-707)]
--- HDR
Defaults

--- Deconvolution
Parameter [Primary PSF] set to [Moffat Beta=4.765 (Trujillo)]
Parameter [Tracking Propagation] set to [During Regularization (Quality)]
Parameter [Primary Radius] set to [1.3 pixels]
--- Color

Duoband preset (defaults parameter [Matrix] to [HOO Duoband 100R,50G+50B,50G+50B])

Parameter [Bright Saturation] set to [4.70]
Parameter [Red Bias Reduce] set to [6.91] to boost the blue/teal of the O-III to taste
--- Psycho-Visual Grain Equalization De-Noise (switch signal evolution tracking off, choose 'Grain Equalize')
Parameter [Grain Size] set to [7.0 pixels]
Parameter [Grain Removal] set to [60 %]

(I think I bumped up the saturation just a little afterwards in the Color module)

Hope that helps!

Edited March 8, 2020 by jager945

[Adreneline]

7 hours ago, jager945 said:

Apologies for any confusion Adrian! The two datasets were used by StarTools to automatically;

• Create a synthetic luminance master (e.g. making the proper blend of 920s of O-III + and 2280s of Ha). You just tell ST the exposure times and it figures it out, but it in this instance, it would have calculated a signal precision of 1.77:1 (Ha:O-III), derived from sqrt(2880/920) for Ha vs sqrt(920/920). So I believe that would have yielded a 1/(1+1.77) * 100% = ~36% OIII vs 1.77/(1+1.77) * 100% = ~64% Ha blend.
• Create a synthetic chrominance master at the same time (e.g. mapping Ha to red, O-III to green and also blue)

Thanks very much for the clarification. It is interesting to see and understand the approach used by ST. I'll give it a go and see what difference it makes.

I am sure the rest of your post will have been of interest to ST users.

Thanks again for your help.

Adrian

[vlaiv]

7 hours ago, jager945 said:

Apologies for any confusion Adrian! The two datasets were used by StarTools to automatically;

• Create a synthetic luminance master (e.g. making the proper blend of 920s of O-III + and 2280s of Ha). You just tell ST the exposure times and it figures it out, but it in this instance, it would have calculated a signal precision of 1.77:1 (Ha:O-III), derived from sqrt(2880/920) for Ha vs sqrt(920/920). So I believe that would have yielded a 1/(1+1.77) * 100% = ~36% OIII vs 1.77/(1+1.77) * 100% = ~64% Ha blend.
• Create a synthetic chrominance master at the same time (e.g. mapping Ha to red, O-III to green and also blue)

In this particular case, this approach to creating synthetic luminance is quite wrong. You can try it out - do 64% / 36% mix and do for example 90% / 10% and look at resulting SNR (take a piece of nebula and measure average signal after removing background / gradients and take pure background and measure standard deviation, or just take rather uniform piece of nebula and measure both average signal and stddev).

Above approach actually works only if you take same signal under same conditions and want to stack two different exposure lengths. In general case - you will not have that, even when stacking same filter data (different conditions over the course of the night - like different LP, different extinction, etc ...).

Best way to / correct way to create synthetic luminance would be to stack both channels (or three channels in case of RGB) with both regular stacking and stddev stacking (which ever method for stacking one might be using - they can also use appropriate standard deviation calculation for set of pixel values that go into stack / weights adjusted, etc ...). You adjust stddev to account for number of stacked frames - SNR improvement (in simple average stacking - you divide with square of number of stacked frames), and you wipe background from regular stacked image. This will give you signal and noise for each pixel in each channel.

Next thing you do is solve the following:

( (S1+S2*a) / sqrt(N1^2+(N2*a)^2) )' = 0

for a (or in case that you are mixing more channels - a1, a2 - one less than number of channels) - for each pixel and apply per pixel weights in mixing two images.

(above equation stands for -  SNR of result needs to be maximized for selected coefficient a, so we solve derivative of total SNR is equal to 0 for certain a).

 

[jager945]

31 minutes ago, vlaiv said:

this approach to creating synthetic luminance is quite wrong.

Ok. 🤗