Processing Example

Protecting background and stars

by Alejandro Tombolini


Image of TingTing44 publicated in General. Generate a mask to protect at the same time background and stars. Main notes: Starmask and StarAlignment tools for creation of the starmask and PixelMath to substract from Lmask. Date: February 2015.

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Image Data

  • Object: Andromeda
  • Author: Tingting44


To protect at the same time background and stars you can substract a starmask from a Lmask.

In this example, the information on the starmask obtained with starmask tool is enhanced with a structure map of the image which aim to include in the mask the stars that are over the galaxy.

Lmask could be previously fine tuned with HistogramTransformation tool to darkness the background if you wish to have a better protection. Also can be applied intensity transformations as LocalHistogramEqualization to better contrast of the structures in the galaxy.

Generate Lmask extracting it with ChannelExtraction or directly from the icon in the image Tool bar in the menu.


Generate StarMask using StarMask Tool. Fine tune the Noise theshold and Scale parameters to include the big stars of the images. Use Truncation when needed to improve protection in the cores of mask structures.


Use StarAlignment tool to generate a structure map of the image.


Regenerate the star profile in the structure map first using MorphologicalTransformation tool to enlarge the stars.


Finally smooth a little with MultiscaleLinearTransform deleting layers 1,2 and 3.


With PixelMath add starmask to structure map and substract it from Lmask.



Last Update: 27/11/2023 03:57 UT