Please let me know if anyone sees any errors or has any additional advice they think helpful.
I will update this post as needed.
To see a full alphabetical list of module topics click here.
Narrowband Accent module (NBAccent) Use (v1.8+)
Purpose:
- To simplify the adding of narrowband accents to visual spectrum images.
This module, and the changes to other modules, greatly simplifies the adding of narrowband accents to an image. After the initial loading of the data this work can now be done in one module.
The narrowband data is processed in parallel to the other data 'behind the scenes' by the Bin, Crop and Wipe modules.
Since the purpose of the narrowband data is in this case to accentuate the visual data the narrowband data is processed independently from, but parallel to, the main dataset.
Useful Sources
For a general overview see NBAccent: Adding Narrowband Accents to Visual Spectrum Datasets.
When to use:
- When you want the narrowband data to accentuate certain elements - and not to contribute to the luminance or chrominance of the main data.
- Use the narrowband data either to supplement LRGB, or to accent it - don't use it for both.
- For example - don't include Ha as luminance if you want to use it for accents.
- If you want the narrowband data to contribute to the luminance or chrominance of the main data use the Compose module instead.
- Use it when you want to:
- Accentuate areas of H-II in galaxies.
- Accentuate large scale background nebulosity.
- Accentuate features in planetary nebulae and other objects.
- Good candidate datasets for accentuating are:
- Ha, O-III or Ha + O-III datasets
- Datasets from OSC and DSLRs taken using duo/tri/quad band filters with narrow spectral responses.
- This is best used after the Color module and before the Denoise module (Tracking off).
AutoDev-{Lens}-Bin-Crop-Wipe-AutoDev (or FilmDev)-{Contrast/HDR/Sharp/SVDecon}-Color-{Shrink/Filter/Entropy/SuperStr/NBAccent}-Track/NR(Unified-Denoise)-{Flux/Repair/Heal/Layer/Synth}
Key: {...} optional modules
Example Workflow (v1.9):
OptiDev-{Lens}-Bin-Crop-Wipe-OptiDev (or FilmDev)-{Contrast/HDR/Sharp/SVDecon}-Color-{Shrink/Filter/Entropy/SuperStr/NBAccent}-Track/NR(Unified-Denoise)-{Flux/Repair/Heal/Layer/Synth}
Key: {...} optional modules
Method:
This is a way of using the module which should give good results in most cases:
- The narrowband data must have been loaded previously in the Compose module:
- Add your luminance and RGB data as normal.
- Press 'NBAccent' button and navigate to and load the narrowband data file.
- Select the 'NBAccent Type' which best describes the data just added, and which selects the R, G or B channels you want to use to highlight.
- The RoI will be inherited from the AutoDev module - change this if needed.
- Adjust 'Ignore Fine Detail <' to remove any noise and other small detail you don't want to be accentuated.
- Other parameters are normally left at their defaults but may be adjusted as described below.
- Press 'Next'.
Page 2: Image Accentuation colouring and brightness. - Depending on the subject - press the associated preset - 'nebula' or 'galaxy'.
- Set 'Response Simulation' to the colouring appropriate to the narrowband channel(s) in the data.
- Set the 'Strength' parameter to give the right emphasis to the accents.
- [v1.8] Set the 'Luminance Modify' to define how much you want the luminance of the image to be modified by the accent.
- [v1.8] Set the 'Color Modify' to define how much you want the colour of the image to be modified by the accent.
- [v1.9] Set the 'Luminance Modify Input' to define how you want the luminance of the image to be modified by the accent.
- [v1.9] Set the 'Color Modify Input' to define how you want the colour of the image to be modified by the accent.
- Set the 'Detail Size' to limit the size of the elements that appear as accents.
- Other parameters are normally left at their defaults but may be adjusted as described below.
- Press 'Keep' when done.
- The accents should be clear and well balanced with the rest of the image.
- If used after the Color module then the usual next step is to turn off Tracking and use the Denoise module.
Screen 1: Signal Stretch and contribution calibration
This stage is to allow you to control which areas will receive the narrowband accentuation.
It is similar in process to the AutoDev module.
A major difference is the way the data is presented. Areas not being enhanced will be made black.
The centres of saturated stars are made black
RoI
Sets the limits of the rectangle representing the Region of Interest (RoI) in pixels.
- The RoI is initially inherited from the AutoDev settings.
Allows NBAccent to ignore small features such as noise below a certain level when allocating dynamic range.
- Particularly important when the image has a low signal to noise ratio (SNR).
- Increase to exclude noise - usually until the image doesn't darken any more.
- Increasing the value also allows the module to concentrate on larger objects and structures in the image.
- The module always makes an exception for very fine but bright details. So star cores will always be handled so as not to get blown out.
- Look for areas that turn black as you increase this parameter. These will be excluded from the augmentation.
- Default is Off. Range is Off then 1.1 to 50.0 pixels.
Defines how much dynamic range to reserve for outside the Region of Interest (ROI).
- Reduce if you have a high dynamic range subject and you want to allocate more dynamic range to the subject.
- Avoid NBAccent clipping the data by never reducing this value to 0%.
- Increase if there is some detail outside the ROI which you want to show up.
- Defaults to 15%. Range is 0% to 100%.
Allows removal of the fainter signal in the narrowband data.
- This parameter should only be used as a last resort.
- Used, for example, where the narrowband data is of very poor quality.
- This may be needed to avoid background imperfections causing unwanted accents.
- The areas not included for augmentation will be turned black.
- Default is 0%. Range is 0 to 100%.
Sets how much linearity is applied to the shadows - before non-linear stretching takes over.
- Values above 50% allocate more dynamic range to the shadows and background.
- Values below 50% allocate more dynamic range to the highlights and foreground.
- Default is 50%. Range is from 0% to 100%.
Nebula preset
This applies settings that accentuate detail in our own galaxy - the Milky Way.
Galaxy preset
This applies settings that accentuate smaller detail in other galaxies.
Strength
This setting controls the overall strength of the accentuation.
- Default is 100%. Range is 0% to 200%.
For cases where the narrowband data has two narrowband signals.
This controls the balance between the two signals.
- Relevant if a duo/tri/quad band filter is used.
- Default is 50%/50%. Range is 0%/100% to 100%/0%.
Optional Gamma correction.
- Default is 1.00. Range is 0.00 to 10.00.
Controls how much the colour of the master image is modified by the selected narrowband data.
- Default is 100%. Range is 0% to 100%.
Controls how the colour of the master image is modified by the narrowband accent data.
- Off: The narrowband accent data input has no effect on the colour of the final image.
- Max of Channel:
- Luminance: The narrowband input luminance controls the colour of the accents in the final image. Where the narrowband luminance is highest the final image colour will be most affected.
- Target Response:
- Source Band:
- Default is Luminance. Range is: Off, Max of Channel, Luminance, Target Response, Source Band.
Controls how much the luminance of the master image is modified by the narrowband accent data.
- Default is 100%. Range is 0% to 100%.
Controls how the luminance of the master image is modified by the selected narrowband data.
- Off: The narrowband accent data input has no effect on the luminance of the final image.
- Max of Channel:
- Luminance: The narrowband accent data input luminance controls the luminance of the accents in the final image. Where the narrowband luminance is highest the final image brightness will be most affected.
- Target Response:
- Source Band:
- Default is Luminance. Range is: Off, Max of Channel, Luminance, Target Response, Source Band.
Brightness Correlation
Defines how much detail must exist in the master image before it is enhanced by the accents.
- Default is 0% (Nebula) 50% (Galaxy). Range is 0% to 100%.
Defines how the narrowband data should be represented in the visual spectrum.
The narrow band red, green & blue channels control specific colouring of the main image.
The selection here dictates which channels (R,G or B) are used by StarTools and how they are mapped to a colour.
- Mapping options are:
- Ha/S-II (Pure Red) - R controls a pure deep red accent. Makes Ha/S-II accents stand out. Use Compose 'NB Accents Type' setting 'Ha/S-II from NB filter'
- HII/Balmer Series (Purple) - R controls a red/purple accent. Use where the R channel represents strong H-II and Balmer series emissions.
- HB/O-III (Cyan) - G & B control a cyan accent. Use where the G & B channels represent Hb & O-III emissions.
- O-III (Teal) - G & B control a teal accent. Use where the G & B channels represent O-III emissions.
- Ha/S-II (Pure Red) + Hb/O-III (Cyan) - R -> deep red, G & B -> Cyan. Use where multi-band filters have captured Ha/S-II and Hb/O-III emissions.
- Ha/S-II (Pure Red) + O-III (Teal) - R -> deep red, G & B -> Teal. Use where multi-band filters have captured Ha/S-II and O-III emissions.
- HII/Balmer Series (Red/Purple) + Hb/O-III (Cyan) - R -> red/purple, G & B -> Cyan. Use where multi-band filters have captured H-II/Balmer series and Hb/O-III emissions.
- HII/Balmer Series (Red/Purple) + O-III (Teal) - R -> red/purple, G & B -> Teal. Use where multi-band filters have captured H-II/Balmer series and O-III emissions.
- Important: In the Compose module you must choose the right 'NB Accents Type' setting to allow the R,G or B channel(s) you want to use to be available here: 'Ha/S-II from NB filter' for R only, 'O-III/Hb from NB filter' for G and B only, and 'Ha/S-II+O-III/Hb from Duo/Tri/Quadband Filter' for R, G and B.
- Default is 'HII/Balmer Series (Purple)'
Sets the maximum size of the detail in the narrowband data that is used to make accents.
- This makes sure only small accents are added - rather than large blobs.
- Setting to 0 pixels means no maximum size.
- Default is 0 pixels (Nebula), 100 pixels (Galaxy). Range is 0 to 100 pixels.
Background Notes:
References to articles on combining Narrowband with LRGB
Article from Light Vortex Astronomy: Tutorial (PixInsight): Combining LRGB with Narrowband
Practice data
There is some suitable data on which to check the NBAccent feature out.
M33 data from Ikarus Observatory data on Stargazers Lounge forum: M33 LRGBHa Data from Ikarus Observatory at SGL
There were some issues with the initial Ha Data - v2 data: M33 LRGBHa Data (v2)
Process the data as described in this forum post.
