Number of Iterations 32 default

Display Iterations: checked (default)

Process high-frequency components only: checked (default).

Now select a few stars with the mouse and click on each one. Try to choose stars that are not too bright or saturated—what we are looking for is "average" stars. As you click on each, you will see the PSF value changing as its PSF is averaged into the group. The PSF Display will show you the PSF that will be used in the deconvolution. The value you get for the PSF is dependent on the profiles of the selected stars, and varies depending on the optics, the camera pixel size, and the seeing conditions present when the image was acquired.

Then click Execute Deconvolution to start the deconvolution. Because this image is larger, iterations take longer than they did with the small planetary image. When it is done, you will need to change the display parameters to compare the two. Select each image and click on the Auto button. You will also find it helps to set the Gamma to a value of 2 to bring out the faint nebulosity. Notice how much sharper the star images are, and how the bright star at X=288, Y=280 is much less bloated. Detail in the nebula is also enhanced.

The value for sigma used in the PSF needs to be carefully chosen in order to avoid dark ring artifacts around stars. The rings are characteristic of Lucy-Richardson deconvolution with the PSF value set too large. By specifying this value through the selection of typical stars in the image, these artifacts can be all but eliminated.

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