Compose module 1.6.386 NGC2903

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JLP
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Compose module 1.6.386 NGC2903

Post by JLP »

Compose module 1.6.386
I would like to fully understand how to use the compose module. I have read many different threads on this and some relate to earlier versions of ST. I have just upgraded from my mirroless camera to a mono camera and filterwheel. ASI1600MMPro EFW with LRGB and Ha filters on a iOptron RC6.
I have taken some images of NGC 2903 and stacked them in DSS 4.2.3 using the first Clear (luminance) frame as the reference for all the other LRGB Ha stacks. This has resulted in 5 fits files
Autosave Lum 1hr 38min.fts, Autosave Red 2hr 30min.fts, Autosave Green 2Hr 34min.fts, Autosave Blue 1hr 36min.fts and Autosave Ha 1hr 40min.fts.
I then created a new Luminance file by composing in L + Synthetic L From RGB, Mono using just the LRGB Autosave files and saving it as NewLum LRGB.tiff. I am doing this because I read somewhere it was the thing to do but why do it and what are the advantages of doing this.
The question is what is the exposure weighting of this file? 9hr 58min(sum of LRGB)?
I then created a new red again using the in L + Synthetic L From RGB, Mono by loading Ha into Lum and my Autosave Red into red. I saved that as NewRed.tiff. Again is the weight of this 4hrs 10min (sum of red and Ha)?
I then use compose L, RGB and loading the NewLum LRGB.tiff into Lum, NewRed.tiff into Red, my Autosave Green file into Green and Autosave Blue file into Blue. Is this what you call LLRGB?
I do not adjust the exposure sliders. There is some confusion here because the manual says pages 108/109 that the Lum Total Exposure slider only has effect when luminance dataset incorporates (L, RGB,……) then latter on page 110 under “L, RGB” it states the exposure settings are ignored. So which is it? I process as normal from here onwards.
When I use Compose Luminance, Color setting L + Synthetic L From RGB, Mono to combine different filter sets does it matter which files I load into the different buttons. Eg is loading Autosave Ha into Luminance and Autosave Red into red the same as loading Autosave Ha into green and Autosave Red into blue? I am assuming that the resulting saved tiff file does not know what color it represents.

If I can create a synthetic Luminance file from just R+G+B do I need to take a Clear (Luminance set)? I have a 5 position filter wheel so if I got an OIII filter and swaped it with the Clear filter am I loosing much but not taking Luminance frames?

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Re: Compose module 1.6.386 NGC2903

Post by admin »

Hi,

Congrats on the new gear!
Using the Compose module/mode has made processing LRGB a lot more straightforward as of 1.5+.
JLP wrote:Compose module 1.6.386
Autosave Lum 1hr 38min.fts, Autosave Red 2hr 30min.fts, Autosave Green 2Hr 34min.fts, Autosave Blue 1hr 36min.fts and Autosave Ha 1hr 40min.fts.
I then created a new Luminance file by composing in L + Synthetic L From RGB, Mono using just the LRGB Autosave files and saving it as NewLum LRGB.tiff. I am doing this because I read somewhere it was the thing to do but why do it and what are the advantages of doing this.
This creates a synthetic luminanc dataset from the L + RGB data and saves it for later use. I'm not sure what the advantage or purpose of that would be without further information.
The advantage/innovation in the new Compose module, is that it processes luminance (or synthetic luminance if you so choose) and color separately, yet simultaneously.
From the documentation;
Compose: Effortless, Signal Evolution-Tracked Composite Creation and Processing

The Compose module is easy-to-use, but extremely flexible compositing and channel extraction tool. As opposed to all other software, the Compose module allows you to effortless process, LRGB, LLRGB, or narrowband composites like SHO, LSHO and more composites, as if they were simple RGB datasets.

In traditional image processing software, composites with separate luminance information (for example acquired through a luminance filter, created by a synthetic luminance frame, or a combination of both), require lengthy processing workflows; luminance (detail) and color information needs (or should!) be processed separately and only combined at the end to produce the final image.

Through the Compose module, StarTools is able to process luminance and color information separately, yet simultaneously.

This has important ramifications for your workflow and signal fidelity;
  • Your workflow for a complex composite is now virtually the same as it is for a simple DSLR/OSC dataset; Modules like Wipe and Color automatically consult and manipulate the correct dataset(s) and enable additional functionality where needed.
  • Because everything is now done in one Tracking session, you get all the benefits from signal evolution tracking until the very end, without having to end your workflow for luminance and start a new one for chroma/color; all modules cross-reference luminance and color information as needed until the very end, yielding vastly cleaner results.
  • The "Entropy" module can consult the chroma/color information to effortlessly manipulate luminance as you see fit, while Tracking monitors noise propagation.
Synthetic luminance dataset are created by simply specifying the total exposure times for each imported dataset. With a click of a button, synthetic luminance datasets can be added to an existing luminance dataset, or can be used as a (synthetic) luminance dataset in its own right.

Usage

Creating a composite is as easy as loading the desired datasets into the desired slots, and optionally setting the desired composite scheme and exposure lengths.

The "Luminance" button loads a dataset into the "Luminance File" slot. The "Lum Total Exposure" slider determines the total exposure length in hours, minutes and seconds. This value is used to create the correct weighted synthetic luminance dataset, in case the "Luminance, Color" composite mode is set to create a synthetic luminance form the loaded channels. Loading a Luminance file will only have an effect when the "Luminance, Color" parameter is set to a compositing scheme that incorporates a luminance dataset (e.g. "L, RGB", "L + Synthetic L From RGB, RGB" or "L + Synthetic L From RGB, Mono") .

The Red, Green and Blue buttons load a dataset in the "Red File", "Green File" and "Blue File" slots respectively. The "Red Total Exposure", "Green Total Exposure", "Blue Total Exposure" sliders determine the total exposure length in hours, minutes and seconds for each of the three slots. These values are used to create the correct weighted synthetic luminance dataset (at 1/3rd weighting of the "Lum Total Exposure"), in case the "Luminance, Color" composite mode is set to create a synthetic luminance from the loaded channels.

Loading an dataset into the "Red File", "Green File" or "Blue File" slots will see any missing slots be synthesised automatically if the "Color Ch. Interpolation" parameter is set to "On". Loading a color dataset into the "Red File", "Green File" or "Blue File" slots will automatically extract the red, green and blue channels of the color dataset respectively.

There are a number of compositing schemes available, some of which will put StarTools into "composite" mode (as signified by a lit up "Compose" label on the Compose button on the home screen). Compositing schemes that require separate processing of luminance and color will put StarTools in this special mode. Some module may exhibit subtly different behaviour, or expose different functionality while in this mode.

The following compositing schemes are selectable;

"RGB, RGB" simply uses red + green + blue for luminance and uses red, green and blue for the color information. No special processing or compositing is done. Any loaded Luminance dataset is ignored, as are Total exposure settings.

"RGB, Mono" simply uses red + green + blue for luminance and uses the average of the red, green and blue channels for all channels for the color information, resulting in a mono image. Any loaded Luminance dataset is ignored, as are Total exposure settings.

"L, RGB" simply uses the loaded luminance dataset for luminance and uses red, green and blue for the color information. Total exposure settings are ignored. StarTools will be put into "composite" mode, processing luminance and color separately but simultaneously. If not Luminance dataset is loaded, this scheme functions the same as "RGB, RGB" with the execption that StarTools will be put into "composite" mode, processing luminance and color separately yet simultaneously.

"L + Synthetic L from RGB, RGB" creates a synthetic luminance dataset from Luminance, Red, Green and Blue, weighted according to the exposure times provided by the "Total Exposure" sliders. The color information will consists of simply the red, green and blue datasets as imported. StarTools will be put into "composite" mode, processing luminance and color separately yet simultaneously.

"L + Synthetic L from RGB, Mono" creates a synthetic luminance dataset from Luminance, Red, Green and Blue, weighted according to the exposure times provided by the "Total Exposure" sliders. The color information will consists of the average of the red, green and blue channels for all channels, yielding a mono image. StarTools is not put into "composite" mode, as no color information is available.

On synthetic luminance generation
For practical purpose, synthetic luminance generation assumes that, besides possibly varying total exposure lengths, all other factors remain equal. E.g. it is assumed that bandwidth response is exactly equal to that of the other filters in terms of width and transmission, and that only shot noise from the object varies (either due to differences in signal in the different filter band from the imaged object, or due to differing exposure times).

When added to a real (non synthetic) luminance filter source, the synthetic luminance's three red, green and blue channels are assumed to contribute exactly one third to the added synthetic luminance. E.g. it is assumed that the aggregate filter response of the individual three red, green and blue channels, exactly match that of the single luminance channel.
The question is what is the exposure weighting of this file? 9hr 58min(sum of LRGB)?
With the above documentation information in hand, the total synthetic synthetic luminance information is 4h51m; Lum 1hr 38min.fts + (Red 2hr 30min.fts + Green 2Hr 34min + Blue 1hr 36min.fts) / 3.
I then created a new red again using the in L + Synthetic L From RGB, Mono by loading Ha into Lum and my Autosave Red into red.
This is not correct/recommended; given that it is assumed that L's weighting is 3x that of red, green and blue. The correct course of action (if you wish to use the exposure sliders as a means to create a blend), is to import Ha and R as a color channel.
I saved that as NewRed.tiff. Again is the weight of this 4hrs 10min (sum of red and Ha)?
Blending wide band and narrowband and then trying to express/understand the aggregate signal as a sum is a little tricky. They are just very different signals; Ha records only a slight portion of the total red signal. Creating this weighting/blend is only really useful to achieve a new color channel.
I then use compose L, RGB and loading the NewLum LRGB.tiff into Lum, NewRed.tiff into Red, my Autosave Green file into Green and Autosave Blue file into Blue. Is this what you call LLRGB?
There are a few names for this (I don't think there is an official scheme). I would call this (SynL)L(R+Ha)RGB, LL(R+Ha)GB, LLRHaGB or similar.
I do not adjust the exposure sliders. There is some confusion here because the manual says pages 108/109 that the Lum Total Exposure slider only has effect when luminance dataset incorporates (L, RGB,……) then latter on page 110 under “L, RGB” it states the exposure settings are ignored. So which is it?
I'm not sure where the confusion is here... Would you be able to elaborate? 108 says;

Code: Select all

Loading a Luminance file will only have an effect when the "Luminance, Color" parameter is set to a compositing scheme that incorporates a luminance dataset (e.g. "L, RGB", "L + Synthetic L From RGB, RGB" or "L + Synthetic L From RGB, Mono") .
110 says;

Code: Select all

"L, RGB" simply uses the loaded luminance dataset for luminance and uses red, green and blue for the color information. Total exposure settings are ignored.
I don't see any contradicting or confusing statements?
When I use Compose Luminance, Color setting L + Synthetic L From RGB, Mono to combine different filter sets does it matter which files I load into the different buttons. Eg is loading Autosave Ha into Luminance and Autosave Red into red the same as loading Autosave Ha into green and Autosave Red into blue? I am assuming that the resulting saved tiff file does not know what color it represents.
Indeed, L is treated differently to R, G or B (see above).
If I can create a synthetic Luminance file from just R+G+B do I need to take a Clear (Luminance set)? I have a 5 position filter wheel so if I got an OIII filter and swaped it with the Clear filter am I loosing much but not taking Luminance frames?
The only reason people tend to take separate Luminance frames is if the R+G+B datasets are intended to be of lesser quality. Luminance requires higher fidelity vs just color information. The most common use case is shooting Luminance at bin 1x1 and shooting color at bin 2x2. This way you spend more time on what is important (e.g. detail/luminance) and less on what it less important (color). The human eye is much more sensitive to luminance fidelity and color fidelity. Other use cases would be to shoot luminance with light pollution filter in place, and color without light pollution filter.

I hope this helps!
Ivo Jager
StarTools creator and astronomy enthusiast
JLP
Posts: 19
Joined: Thu Apr 14, 2016 11:46 am

Re: Compose module 1.6.386 NGC2903

Post by JLP »

Thank you Ivo for your detailed reply. It seems I still have some fundamental misunderstanding of what to take and how to process the files. My decision to go mono was in part due to ST 1.6 having the ability to process multiple filtered files in a simpler way than other software. I have not yet achieved the optimum in Astro image processing but do not think I could achieve anywhere near what I am getting without the help from Startools, so thank you.

I think I now understand the the difference of combining files between Lum and RGB buttons. NGC 2903 is suppose to have some HII in its core that's why I have taken Ha. Is it best to combine this in the colour channels and then use a replacement red or green?
admin wrote:Hi,
I do not adjust the exposure sliders. There is some confusion here because the manual says pages 108/109 that the Lum Total Exposure slider only has effect when luminance dataset incorporates (L, RGB,……) then latter on page 110 under “L, RGB” it states the exposure settings are ignored. So which is it?
I'm not sure where the confusion is here... Would you be able to elaborate? 108 says;

Code: Select all

Loading a Luminance file will only have an effect when the "Luminance, Color" parameter is set to a compositing scheme that incorporates a luminance dataset (e.g. "L, RGB", "L + Synthetic L From RGB, RGB" or "L + Synthetic L From RGB, Mono") .
110 says;

Code: Select all

"L, RGB" simply uses the loaded luminance dataset for luminance and uses red, green and blue for the color information. Total exposure settings are ignored.
I don't see any contradicting or confusing statements?
I am unable to copy the relevant bit of text so have taken an image. The paragraph to me seems to relate to Luminance, Colour and the Lum Total Exposure sliders. "This value is used to create the correct weighted synthetic luminance dataset, ..." I have therefore taken that the exposure sliders matters when using L, RGB because "(e.g. "L, RGB, ..."
But if the result is that when I process an LRGB dataset using Luminace, Colour setting L, RGB I do not have to set the exposure sliders then I can settle for that.
ST text Luminance.jpg
ST text Luminance.jpg (72.13 KiB) Viewed 875 times
If I can create a synthetic Luminance file from just R+G+B do I need to take a Clear (Luminance set)? I have a 5 position filter wheel so if I got an OIII filter and swaped it with the Clear filter am I loosing much but not taking Luminance frames?
The only reason people tend to take separate Luminance frames is if the R+G+B datasets are intended to be of lesser quality. Luminance requires higher fidelity vs just color information. The most common use case is shooting Luminance at bin 1x1 and shooting color at bin 2x2. This way you spend more time on what is important (e.g. detail/luminance) and less on what it less important (color). The human eye is much more sensitive to luminance fidelity and color fidelity. Other use cases would be to shoot luminance with light pollution filter in place, and color without light pollution filter.
In my ignorance I did not think the Luminance frames were that important (until now) in capturing detail and I thought that the reason for going mono was to get more detail in the R + G + B exposures. I have read that binning with CMOS sensors is not necessary, so have not looked at it.

I did process these files using just the LRGB Autosave files and the Luminance, Colour setting L, RGB and then again using just the RGB files and the Luminace, Colour L + Synthetic From RGB, RGB and could not detect any difference?

I think this step from OSC to mono + filters is a much bigger learning curve than I had anticipated. I need to have a deeper study about what I am doing. Thanks again for trying to explain.
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Re: Compose module 1.6.386 NGC2903

Post by admin »

JLP wrote:Thank you Ivo for your detailed reply. It seems I still have some fundamental misunderstanding of what to take and how to process the files. My decision to go mono was in part due to ST 1.6 having the ability to process multiple filtered files in a simpler way than other software. I have not yet achieved the optimum in Astro image processing but do not think I could achieve anywhere near what I am getting without the help from Startools, so thank you.
A mono instrument is the absolute best, most flexible way of imaging the night skies, so congratulations on this big step! :thumbsup: The afforded flexibility comes with some more complexity when it comes to acquisition decisions, but the learning curve shouldn't be too bad. Indeed, ST's Compose mode greatly helps with reducing the complexity of processing such complex composites, while achieving better results.
I think I now understand the the difference of combining files between Lum and RGB buttons. NGC 2903 is suppose to have some HII in its core that's why I have taken Ha. Is it best to combine this in the colour channels and then use a replacement red or green?
This is definitely one popular way of doing it (e.g. create a new red channel from a Ha + R blend). There are alternative techniques too, but they are more complex. I am actually looking to expand the Compose/Color module and Compose mode processing in a future version of StarTools for visual Ha.
I am unable to copy the relevant bit of text so have taken an image. The paragraph to me seems to relate to Luminance, Colour and the Lum Total Exposure sliders. "This value is used to create the correct weighted synthetic luminance dataset, ..." I have therefore taken that the exposure sliders matters when using L, RGB because "(e.g. "L, RGB, ..."
But if the result is that when I process an LRGB dataset using Luminace, Colour setting L, RGB I do not have to set the exposure sliders then I can settle for that.
ST text Luminance.jpg
Thank you. I will revisit whether any clarification is needed in the docs or interface.
In my ignorance I did not think the Luminance frames were that important (until now) in capturing detail and I thought that the reason for going mono was to get more detail in the R + G + B exposures. I have read that binning with CMOS sensors is not necessary, so have not looked at it.
Indeed, hardware binning is getting less important, as the read noise benefits are becoming less with more modern technology.
The overall idea is/was that you spend less time collecting RGB and more time acquiring L. However, these days, a synthetic luminance dataset from "deep" R, G and B may yield results that are almost just as useful and quick to capture. That said, acquiring L is still the "cleanest" way of acquiring detail, as it reduces the amount of variables greatly (e.g. varying seeing, tracking error, flexure, etc. that may affect the 3 color channels differently).
I did process these files using just the LRGB Autosave files and the Luminance, Colour setting L, RGB and then again using just the RGB files and the Luminace, Colour L + Synthetic From RGB, RGB and could not detect any difference?
You should find that the L+SynL - all other things equal - has a cleaner, deeper signal than just L by itself.

Clear skies!
Ivo Jager
StarTools creator and astronomy enthusiast
JLP
Posts: 19
Joined: Thu Apr 14, 2016 11:46 am

Re: Compose module 1.6.386 NGC2903

Post by JLP »

Thanks again Ivo and I look forward to even more improvements in your great product ST. :thumbsup:
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