NB processing help appreciated!

[richbandit]

Guys,

The other day I obtained some NB data of NGC6820, followed by my usual process with APP before going on to process in Star Tools - however, I just can't seem to get a decent result, no matter what combination of settings I try! Admittedly, I haven't done any processing for a couple of months (weather, etc.) but even so .... not had this problem before.

Could be my bad data (quite possible!), or is NGC6820 one of those that just needs many more subs? I took 20 x 180 secs each of Ha, SII and OIII using GT81 'scope and asi183mm pro cooled camera. Night was very clear, so I was surprised. I do notice there was not a lot of SII and OIII data showing, seemed to be all Ha - or is that to be expected with this object? But other images (e.g. on Astrobin) tend to show adequate abundance of all channels.

Any chance one of you very kind people out there might find the time to look at my data - is it just me, or is the data no good?

I've put the stacked files on Dropbox at https://www.dropbox.com/sh/kktdt7o5je3e ... V1OKa?dl=0 - please feel free to download if you wish and offer any advice or comments.

Many thanks in anticipation!

Richard

[admin]

Hi,

I didn't have any particular problems processing your dataset.
Of course, just 1h per band is not very much signal, but there is enough there to show the object;

NewComposite.jpg (512.39 KiB) Viewed 2306 times

Usually, Ha is by far the strongest signal, so it is not too unexpected for the O-III and S-II signal to be weak but in StarTools that is not a problem (detail and color is processed separately as you know).

Processed in ST 1.8a (preview to be released soon to anyone interested; EOI here);

--- Compose
Parameter [Luminance, Color] set to [L + Synthetic L From RGB, RGB]
Parameter [Color Ch. Interpolation] set to [On]
Parameter [UNKNOWN] set to [Ha/S-II from NB filter]
Parameter [Lum Total Exposure] set to [Not set]
Parameter [Blue Total Exposure] set to [1h00m (60m) (3600s)]
Parameter [Green Total Exposure] set to [1h00m (60m) (3600s)]
Parameter [Red Total Exposure] set to [1h00m (60m) (3600s)]
Image size is 5512 x 3694
Type of Data: Linear, was not Bayered, or was Bayered + white balanced
--- Auto Develop
Parameter [Ignore Fine Detail <] set to [Off]
Parameter [Outside RoI Influence] set to [15 %]
Parameter [RoI X1] set to [0 pixels]
Parameter [RoI Y1] set to [0 pixels]
Parameter [RoI X2] set to [5512 pixels (-0)]
Parameter [RoI Y2] set to [3694 pixels (-0)]
Parameter [Detector Gamma] set to [1.00]
Parameter [Shadow Linearity] set to [50 %]
--- Bin
Parameter [Scale] set to [scale 25.00% / +4.00 bits / +3.00x SNR improvement]
Image size is 1378 x 923
--- Crop
Parameter [X1] set to [23 pixels]
Parameter [Y1] set to [20 pixels]
Parameter [X2] set to [1357 pixels (-21)]
Parameter [Y2] set to [904 pixels (-19)]
Image size is 1334 x 884
--- Wipe
Parameter [Synthetic Dark/Bias] set to [Off]
Parameter [Gradient Edge Behavior] set to [Absorb 50%]
Parameter [Synthetic Flats] set to [Off]
Parameter [Correlation Filtering] set to [Off]
Parameter [Sampling Precision] set to [256 x 256 pixels]
Parameter [Dark Anomaly Filter] set to [1 pixels]
Parameter [Gradient Falloff] set to [0 %]
Parameter [Synth. Bias Edge Area] set to [100 %]
Parameter [Gradient Aggressiveness] set to [75 %]
Redoing stretch of linear data
--- Auto Develop
Parameter [Ignore Fine Detail <] set to [Off]
Parameter [Outside RoI Influence] set to [15 %]
Parameter [RoI X1] set to [0 pixels]
Parameter [RoI Y1] set to [0 pixels]
Parameter [RoI X2] set to [1334 pixels (-0)]
Parameter [RoI Y2] set to [884 pixels (-0)]
Parameter [Detector Gamma] set to [1.00]
Parameter [Shadow Linearity] set to [17 %]
--- Contrast
Parameter [Expose Dark Areas] set to [Yes]
Parameter [Brightness Retention] set to [Off]
Parameter [Precision] set to [256 x 256 pixels]
Parameter [Shadow Detail Size] set to [10 pixels]
Parameter [Locality] set to [50 %]
Parameter [Shadow Dyn Range Alloc] set to [50 %]
--- Spatially Variant PSF Deconvolution
Parameter [PSF Resampling] set to [None]
Parameter [Synthetic PSF Model] set to [Circle of Confusion (Optics Only)]
Parameter [Sampled Area] set to [15x15]
Parameter [Synthetic PSF Radius] set to [1.5 pixels]
Parameter [Synthetic Iterations] set to [Off]
Parameter [Spatial Error] set to [1.00]
Parameter [Deringing Fuzz] set to [20.0 pixels]
Parameter [Deringing] set to [50 %]
Parameter [Dyn. Range Extension] set to [1.00]
Parameter [Linearity Cutoff] set to [85 %]
Parameter [Sampled Iterations] set to [10x]
--- Color
Parameter [Bias Slider Mode] set to [Sliders Reduce Color Bias]
Parameter [Style] set to [Artistic, Not Detail Aware]
Parameter [LRGB Method Emulation] set to [RGB Ratio, CIELab Luminance Retention]
Parameter [Matrix] set to [SHO 40SII+60Ha,70Ha+30OIII,100OIII]
Parameter [Dark Saturation] set to [3.6]
Parameter [Bright Saturation] set to [2.0]
Parameter [Saturation Amount] set to [264 %]
Parameter [Blue Bias Reduce] set to [1.00]
Parameter [Green Bias Reduce] set to [4.36]
Parameter [Red Bias Reduce] set to [1.35]
Parameter [Mask Fuzz] set to [1.0 pixels]
Parameter [Cap Green] set to [0 %]
Parameter [Highlight Repair] set to [8 pixels]
--- Super Structure
Parameter [Detail Preservation] set to [Linear Brightness Mask Darken]
Parameter [Compositing Algorithm] set to [Multiply, Gamma Correct]
Parameter [Brightness, Color] set to [Process Both]
Parameter [Brightness Retention] set to [Local Median]
Parameter [Mask Fuzz] set to [1.0 pixels]
Parameter [Airy Disk Radius] set to [50 %]
Parameter [Gamma] set to [0.75]
Parameter [Detail Preservation Radius] set to [20.0 pixels]
Parameter [Saturation] set to [50 %]
Parameter [Strength] set to [100 %]
--- Unified De-Noise
Parameter [Grain Size] set to [18.1 pixels]
Parameter [Walking Noise Size] set to [1.0 pixels]
Parameter [Walking Noise Angle] set to [0]
--- Unified De-Noise
Parameter [Scale 1] set to [99 %]
Parameter [Scale 2] set to [95 %]
Parameter [Scale 3] set to [95 %]
Parameter [Scale 4] set to [95 %]
Parameter [Scale 5] set to [50 %]
Parameter [Equalized Grain] set to [0 %]
Parameter [Scale Correlation] set to [50 %]
Parameter [Color Detail Loss] set to [50 %]
Parameter [Brightness Detail Loss] set to [50 %]
Parameter [Grain Dispersion] set to [18.1 pixels]

Hope that helps!

[richbandit]

Hi Ivo,

Many thanks indeed for your response, and especially for sharing your process.

As expected, your result is much better than my attempt, and it's highlighted a number of areas where my processing was incorrect! In particular:

1. I generally try not to bin if I can get away with it, to try to retain as much detail as possible; when I do I tend to stick to 50%, certainly no more than 35%. However, your setting of 25% has indeed made a difference. So, my theory is obviously completely wrong - I guess by not binning so much I've been retaining too much noise?
2. Wipe - I've tended to keep and use default values, but again your setting of 'show linearity' (reduced from default 50% to 17%) made a noticeable difference.
3. Decon - same here, I've tended to keep 'mask fuzz' at default 8px - increasing to 20px as you did helped further.
4. Superstructure - I confess to not having used this before (my bad!). Following your procedure added further detail, so must use in future!
5. Finally - the big one for me I suspect - denoise (tracking off). I've always tried to keep the grain size setting as low as I can reasonably get away with, on the basis that the higher this is the more possibility of erasing too much 'real' data. I nearly fell off my chair when I saw you'd set it to 18.1px!! But, using that setting certainly made the biggest difference to my eyes.

So, I've learned that I need to take more care over certain key settings (particular those as above!). I've run through the process again following your settings and yes, arrived at the same final result as you.

Once again, many thanks indeed Ivo - this has been an enormous help to me!

Kind regards,

Richard