Repair Module Use

Notes from users, documentation addendums.

Repair Module Use

Postby Guy » Wed Apr 12, 2017 5:27 pm

Here are some notes relating to using this module. It is not the only way to use the module and experimentation is encouraged.
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

Repair Module

  • To detect and automatically repair star defects such as those caused by blooming, guiding errors, bad polar alignment, collimation problems, or mirror defects such as astigmatism.
For a general overview see Repair: Star Rounding and Repair. The Repair module is used to repair severely deformed stars. It complements the Magic module which is used if you just want to reduce the stars size.

Useful Sources
The Unofficial guide is also a good source of help. It relates to version 1.3.5 so there may have been some changes. The notes below relate to StarTools version 1.4.
The processing video M8 in Color with modest data has a demonstration of the Repair module between 10m12s and 13m16s

When to use:
  • Can only be used when Tracking is off. Towards the end of the processing workflow.
  • Can be used more than once. Using different algorithms perhaps.
Example Workflow:
AutoDev-{Band/Lens}-Bin-Crop-Wipe-AutoDev(or Develop)-{As needed: Decon/Sharp/Contrast/HDR/Flux/Life}-Color-{Filter}-Denoise-{If needed: Layer/Magic/Heal/Repair/Synth}
Key: {...} optional modules

This is a way of using the module To improve the shape of the stars - which should give good results in most cases:
  1. Create a star mask Mask-Auto-Stars-Keep making sure that the stars in the mask are separated by at least one 'off' pixel.
  2. Load the Repair module.
  3. Select the Algorithm - Warp for oval stars, One of the Redistribute modes for more heavily distorted stars.
  4. You can usually leave all other settings at the default values.
  5. Experiment with the settings if the results aren't right.
  6. 'Keep' the result.
What result to look for:
  • Stars should be round and the colour should be well distributed.
  • Check for artefacts around the corrected stars - increase Grow Mask if they exist.
  • Check for places where two stars have merged into one - if found make sure that all stars in the mask are separated by at least one 'off' pixel.
After Use:
  • Consider using other modules that require Tracking to be off - like Heal, Magic and Synth.
Description of Controls:

For general instructions on using masks see Mask
  • For best results make sure that in the mask all stars are separated by one 'off' pixel - otherwise the stars may be merged.
Sets the algorithm the Repair module uses when repairing stars:
  • Warp - rounds stars by warping them into shape.
  • Redistribute, Core is Avg Location - Tries to redistribute all starlight pixels. Use where stars are severely distorted by astigmatism or heavy coma
  • where starlight is scattered, out of focus (doughnuts) or otherwise badly distorted. Tries to find the original centre of the star by averaging all the sample locations.
  • Redistribute, Core is Brightest Pixel - As above but sets the centre of the star based on the brightest pixel.
  • Debloom (Vertical Streaks) - Tries to recover stars that were affected by CCD blooming. Assumes bloom is in a straight vertical direction and there is negligible rotation.
Grow Mask:
Sets the amount to temporarily grow the mask by.
  • Use a higher value if you can see artefacts around corrected stars.
  • Default is 1 pixel. Range is 0 to 10 pixels.
Radial Samples:
Applies to the Warp algorithm only - Sets the number of samples taken to determine the roundness of a star.
  • A higher value may be needed to correct severely distorted stars but will be slower.
  • Default is 32. Range is 16, 32 or 64.
Sub Sampling
Applies to the Warp algorithm only - Sets the number of subsamples per pixel to use while creating the Radial Samples.
  • A higher value may make the stars more precisely round but will be slower.
  • Default is 4x. Range is 2x, 4x or 8x.
Background Notes:
The Repair module allows for the correction of more complex aberrations than the much less sophisticated 'offset filter & darken layer' method, whilst retaining the star's exact appearance and color.

The repair module comes with two different main algorithms:
  • The 'Warp' algorithm uses all pixels that make up a star and warps them into a circular shape. This algorithm is very effective on stars that are oval or otherwise have a convex shape.
  • The 'Redistribution' algorithm uses all pixels that make up a star and redistributes them in such a way that the original star is reconstructed. This algorithm is very effective on stars that are concave or otherwise heavily distorted, such as stars that look more like patches of light without a distinct core which cannot be repaired using the 'Warp' algorithm.
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