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Author Topic: PixInsight - Updated Narrow Band Workflow (Long Post and Large Image Warning)  (Read 5853 times)

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Offline chris.bailey

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There have been a number of changes in PixInsight over the past few months and together with reading others workflows has led me to review my own standard workflow for narrowband images; mono Ha in particular. I thought it might be useful to share it.

As ever with PixInsight some degree of experimentation is key so don't take my exact settings as gospel, they do need tweaking due to conditions and the particular characteristics of your setup. Mono image presentation is also open to a degree of personal style, I like a bit more contrast in my images than many. Hopefully, though, this will provide a few ideas to some people but equally any builds on this are very welcome.

I have posted full sized screen shots as down-sampling tends to make the text unreadable, apologies to those who are monitorally challenged.

This is not a full PixInsight Tutorial!

Chris

ps I still do my calibration long-hand rather than using the batch pre-processing script.

pps not long after taking this image set I discovered that the focuser tube on my FSQ had some discernible play. It has since been stripped down and adjusted!
LX200|ZS70|FSQ85|FLT110|Altair DF250RC|EQ6 Pro(Rowan Belt Mod)|ParamountMX
ATIK383L+/EFW2/OAG|Lodestar|Baader 36mm LRGBHaSIIOIII
Starlight Express SXVRH16/ONAG/FW|Lodestar X2|Baader 2" Filters
Starlight Express SXVRH814/ONAG/FW|LodestarX2|Baader 2" Filters
Lunt LS60PTBF1200|DMK41|Quark Chromo
Samyang 135mm f1.8

Offline chris.bailey

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Re: PixInsight - Updated Narrow Band Workflow (Large Image Warning)
« Reply #1 on: 10:54:55, 06 November, 2015 »
1.Blink

Having backed up the base frames the first thing I do is Blink through the image set [Image Inspection>Blink] and MOVE any that don't come up to scratch to a REJECTED folder. It is quite heart-breaking to cull long narrowband subs but it is important to be quite ruthless. If you have less than say 12 images, it is important to remove any with satellite/plane trails as the tight rejection criteria needed to get rid of them from the stack can be detrimental to the final result.

I remove any at this stage that have a visually lower signal than the rest. Several images in this set were affected by passing bands of high cloud i.e. a pretty normal night!
LX200|ZS70|FSQ85|FLT110|Altair DF250RC|EQ6 Pro(Rowan Belt Mod)|ParamountMX
ATIK383L+/EFW2/OAG|Lodestar|Baader 36mm LRGBHaSIIOIII
Starlight Express SXVRH16/ONAG/FW|Lodestar X2|Baader 2" Filters
Starlight Express SXVRH814/ONAG/FW|LodestarX2|Baader 2" Filters
Lunt LS60PTBF1200|DMK41|Quark Chromo
Samyang 135mm f1.8

Offline chris.bailey

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Re: PixInsight - Updated Narrow Band Workflow (Large Image Warning)
« Reply #2 on: 10:55:39, 06 November, 2015 »
2. Image Calibration

It is important to get the tick boxes right on this one.

BIAS frame calibration should be left unticked.

If you have not previously BIAS subtracted your DARK frames then calibration should be ticked and if your DARK frames don't match the LIGHT frames exactly (duration and temperature) then tick the optimisation tickbox.

I always BIAS subtract my FLAT frames prior to Flats integration so calibration of the FLATS should be unticked as they have already been done.

NB with shorter subs on the SX814 Sony sensor I don't bother with DARK's but with 20 minute frames I do see some small benefit in using them but though they are a pain to collect in sufficient numbers
LX200|ZS70|FSQ85|FLT110|Altair DF250RC|EQ6 Pro(Rowan Belt Mod)|ParamountMX
ATIK383L+/EFW2/OAG|Lodestar|Baader 36mm LRGBHaSIIOIII
Starlight Express SXVRH16/ONAG/FW|Lodestar X2|Baader 2" Filters
Starlight Express SXVRH814/ONAG/FW|LodestarX2|Baader 2" Filters
Lunt LS60PTBF1200|DMK41|Quark Chromo
Samyang 135mm f1.8

Offline chris.bailey

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Re: PixInsight - Updated Narrow Band Workflow (Large Image Warning)
« Reply #3 on: 11:00:19, 06 November, 2015 »
3. Sub Frame Selector Script

I have only recently started using this. It is a bit time consuming but can spot 'dodgy' frames that are not necessarily visual apparent. It is very customisable!

The script measures all the input frames and gives a wealth of information (too much?) about them that may not be obvious visually. For me there are two important parameters, FWHM and Eccentricity. The script enables the setting of approval parameters to reject all images that don't meet the criteria set. Plots help visualise how the images vary within the criteria bounds set. Finally the script can be setup to mark images as approved or rejected and even move rejected images to a REJECTED folder.

Setting the rejection criteria can be quite sensitive but images can be manually ticked to approve them, if say a rejection criteria of <= 3.0 FWHM is set and one image has a FWHM of 3.05 then I would manually approve that for inclusion.

NB many people use FWHMSigma and EccentricitySigma in their expression settings but I find I have a better feel for straight FWHM and Eccentricity.
LX200|ZS70|FSQ85|FLT110|Altair DF250RC|EQ6 Pro(Rowan Belt Mod)|ParamountMX
ATIK383L+/EFW2/OAG|Lodestar|Baader 36mm LRGBHaSIIOIII
Starlight Express SXVRH16/ONAG/FW|Lodestar X2|Baader 2" Filters
Starlight Express SXVRH814/ONAG/FW|LodestarX2|Baader 2" Filters
Lunt LS60PTBF1200|DMK41|Quark Chromo
Samyang 135mm f1.8

Offline chris.bailey

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Re: PixInsight - Updated Narrow Band Workflow (Large Image Warning)
« Reply #4 on: 11:00:56, 06 November, 2015 »
4. Star Alignment

To register all images to a reference. I have reverted to using a BiCubic Spline interpolation algorithm as I find Lanczos interpolation to create undershoot ringing on images taken with my SX814. With dithered sub frames this is less of an issue but can still give some dark halos around brighter stars. Setting this to Auto will work for most people but some experimentation can be worthwhile.
LX200|ZS70|FSQ85|FLT110|Altair DF250RC|EQ6 Pro(Rowan Belt Mod)|ParamountMX
ATIK383L+/EFW2/OAG|Lodestar|Baader 36mm LRGBHaSIIOIII
Starlight Express SXVRH16/ONAG/FW|Lodestar X2|Baader 2" Filters
Starlight Express SXVRH814/ONAG/FW|LodestarX2|Baader 2" Filters
Lunt LS60PTBF1200|DMK41|Quark Chromo
Samyang 135mm f1.8

Offline chris.bailey

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Re: PixInsight - Updated Narrow Band Workflow (Large Image Warning)
« Reply #5 on: 11:01:33, 06 November, 2015 »
5. Image Integration

Having been pretty ruthless with image rejection, only 11 remain to be stacked. This is borderline for using a sigma clipping rejection but it does give better results with >10 images.

LX200|ZS70|FSQ85|FLT110|Altair DF250RC|EQ6 Pro(Rowan Belt Mod)|ParamountMX
ATIK383L+/EFW2/OAG|Lodestar|Baader 36mm LRGBHaSIIOIII
Starlight Express SXVRH16/ONAG/FW|Lodestar X2|Baader 2" Filters
Starlight Express SXVRH814/ONAG/FW|LodestarX2|Baader 2" Filters
Lunt LS60PTBF1200|DMK41|Quark Chromo
Samyang 135mm f1.8

Offline chris.bailey

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Re: PixInsight - Updated Narrow Band Workflow (Large Image Warning)
« Reply #6 on: 11:04:42, 06 November, 2015 »
6. Crop

With all images it is worth cropping off a few pixels from the image edges. With dithered images this can sometimes need to be more.
LX200|ZS70|FSQ85|FLT110|Altair DF250RC|EQ6 Pro(Rowan Belt Mod)|ParamountMX
ATIK383L+/EFW2/OAG|Lodestar|Baader 36mm LRGBHaSIIOIII
Starlight Express SXVRH16/ONAG/FW|Lodestar X2|Baader 2" Filters
Starlight Express SXVRH814/ONAG/FW|LodestarX2|Baader 2" Filters
Lunt LS60PTBF1200|DMK41|Quark Chromo
Samyang 135mm f1.8

Offline chris.bailey

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7. Parameters for MURE De Noise Script

The Mure De Noise Script needs values for the Sensor Gain and an estimate for Gaussian Noise. The former can be obtained from manufacturer data, the latter by putting a couple of dark or bias frames into the [Script>Image Analysis>DarkBiasNoise Estimator] script. The author of both scripts is intending to change the nomenclature of both noise settings to match up.
LX200|ZS70|FSQ85|FLT110|Altair DF250RC|EQ6 Pro(Rowan Belt Mod)|ParamountMX
ATIK383L+/EFW2/OAG|Lodestar|Baader 36mm LRGBHaSIIOIII
Starlight Express SXVRH16/ONAG/FW|Lodestar X2|Baader 2" Filters
Starlight Express SXVRH814/ONAG/FW|LodestarX2|Baader 2" Filters
Lunt LS60PTBF1200|DMK41|Quark Chromo
Samyang 135mm f1.8

Offline chris.bailey

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8. MURE DeNoise Script

This is currently not a part of the standard PI distribution so need to be downloaded from the link here http://pixinsight.com/forum/index.php?topic=9206.0 and then copied into the PixInsight Scripts folder and added via [Script>FeatureScripts>Add]

MUREDeNoise seems to work very well on mono images with a reasonable signal to work with. It does not lead to the "painted" look of many other denoising algorithms and does not lead to background clumpiness. Equally it is very good at preserving fine detail BUT does not remove every grain of noise.

It is an iterative process using the CCD and Noise parameters as a seed. 8 Spin Cycles works well but I see an improvement in upping this to 15. It is quite processor intensive and on this 3300x2700 image, denoising takes about 5 minutes with 15 spin cycles.

Note that MURE DeNoise DOES NOT work with drizzled images and is less successful with those taken over multiple sessions with varying conditions. It only works on monochrome linear images and it should be used before any other operation that may impact on an images levels values including DBE.
LX200|ZS70|FSQ85|FLT110|Altair DF250RC|EQ6 Pro(Rowan Belt Mod)|ParamountMX
ATIK383L+/EFW2/OAG|Lodestar|Baader 36mm LRGBHaSIIOIII
Starlight Express SXVRH16/ONAG/FW|Lodestar X2|Baader 2" Filters
Starlight Express SXVRH814/ONAG/FW|LodestarX2|Baader 2" Filters
Lunt LS60PTBF1200|DMK41|Quark Chromo
Samyang 135mm f1.8

Offline chris.bailey

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9. Dynamic Background Enhance

Placing samples manually is quite critical on many of these extended Ha objects. Only a few samples can still remove large scale gradients.
LX200|ZS70|FSQ85|FLT110|Altair DF250RC|EQ6 Pro(Rowan Belt Mod)|ParamountMX
ATIK383L+/EFW2/OAG|Lodestar|Baader 36mm LRGBHaSIIOIII
Starlight Express SXVRH16/ONAG/FW|Lodestar X2|Baader 2" Filters
Starlight Express SXVRH814/ONAG/FW|LodestarX2|Baader 2" Filters
Lunt LS60PTBF1200|DMK41|Quark Chromo
Samyang 135mm f1.8

Offline chris.bailey

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10. Masked Stretch

This had fallen out of favour with me until I tried reducing the target background and increasing the number of iterations significantly. I also reduce the clipping fraction by several orders of magnitude. Masked Stretch produces tighter stars than doing a normal histogram stretch. It is important to provide Masked Stretch with a background sample via a preview and setting the upper bound of this to a level sampled from within the preview box.
LX200|ZS70|FSQ85|FLT110|Altair DF250RC|EQ6 Pro(Rowan Belt Mod)|ParamountMX
ATIK383L+/EFW2/OAG|Lodestar|Baader 36mm LRGBHaSIIOIII
Starlight Express SXVRH16/ONAG/FW|Lodestar X2|Baader 2" Filters
Starlight Express SXVRH814/ONAG/FW|LodestarX2|Baader 2" Filters
Lunt LS60PTBF1200|DMK41|Quark Chromo
Samyang 135mm f1.8

Offline chris.bailey

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11. HDR Multiscale Transform

I like some contrast in my mono Ha images and it is very easy to overdo it with this tool. 7 or 8 layers with a mask produces a subtle increase in highlight contrast.
LX200|ZS70|FSQ85|FLT110|Altair DF250RC|EQ6 Pro(Rowan Belt Mod)|ParamountMX
ATIK383L+/EFW2/OAG|Lodestar|Baader 36mm LRGBHaSIIOIII
Starlight Express SXVRH16/ONAG/FW|Lodestar X2|Baader 2" Filters
Starlight Express SXVRH814/ONAG/FW|LodestarX2|Baader 2" Filters
Lunt LS60PTBF1200|DMK41|Quark Chromo
Samyang 135mm f1.8

Offline chris.bailey

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12. ACD Noise Reduction

MUREDeNoise does a fine job of noise suppression but can leave some visible noise in the shadows. A subtle application of ACDNR with a strong high signal protection mask can provide some further suppression.
LX200|ZS70|FSQ85|FLT110|Altair DF250RC|EQ6 Pro(Rowan Belt Mod)|ParamountMX
ATIK383L+/EFW2/OAG|Lodestar|Baader 36mm LRGBHaSIIOIII
Starlight Express SXVRH16/ONAG/FW|Lodestar X2|Baader 2" Filters
Starlight Express SXVRH814/ONAG/FW|LodestarX2|Baader 2" Filters
Lunt LS60PTBF1200|DMK41|Quark Chromo
Samyang 135mm f1.8

Offline chris.bailey

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13. Local Histogram Equalisation

Another tool that can be a bit of a contrast sledgehammer but turned right down can lift overall contrast in a much gentler way than resorting to an S-Curve. When the preview looks about right, I tend to turn the amount down by a further 0.1!
LX200|ZS70|FSQ85|FLT110|Altair DF250RC|EQ6 Pro(Rowan Belt Mod)|ParamountMX
ATIK383L+/EFW2/OAG|Lodestar|Baader 36mm LRGBHaSIIOIII
Starlight Express SXVRH16/ONAG/FW|Lodestar X2|Baader 2" Filters
Starlight Express SXVRH814/ONAG/FW|LodestarX2|Baader 2" Filters
Lunt LS60PTBF1200|DMK41|Quark Chromo
Samyang 135mm f1.8

Offline chris.bailey

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14. Histogram Transformation

I used to reach for the histogram tool early in the workflow but now prefer to make a single final adjustment near the end and aim to just clip the shadows by a little whilst stretching the image slightly (to taste). The benefit of doing the second stretch at this stage is that the various contrast enhancement and second stage noise reductions will have had an impact on the histogram and as the stretch can be data destructive it seems best to do it late on.
LX200|ZS70|FSQ85|FLT110|Altair DF250RC|EQ6 Pro(Rowan Belt Mod)|ParamountMX
ATIK383L+/EFW2/OAG|Lodestar|Baader 36mm LRGBHaSIIOIII
Starlight Express SXVRH16/ONAG/FW|Lodestar X2|Baader 2" Filters
Starlight Express SXVRH814/ONAG/FW|LodestarX2|Baader 2" Filters
Lunt LS60PTBF1200|DMK41|Quark Chromo
Samyang 135mm f1.8

 

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