Sky smoothing

In the "Sky" module of Nebulb there is also a tool available to apply a smoothing to the sky.

It is true that image stacking is the most effective technique to reduce noise, but it is also true that when applying large light pollution reductions, some noise is likely to appear in the sky part of the image.

It should be noted that Nebulb's light pollution reduction is very effective and powerful, bringing out all the information underneath the light offset that covers the image. However, this also makes the small amount of noise in the image more visible when light pollution reduction is applied (the more the greater the reduction applied).

That said, by means of the "Smoothing" control of Nebulb it is possible to apply a smoothing to the background of the sky (without affecting the stars at all) in order to reduce the noise that may appear in the final image after applying the light pollution reduction.

IMPORTANT 1: The "Smoothing" tool acts on the sky part of the aligned stars image. For the star trails image this tool is disabled, as the smoothing of the star trails is done during stacking.

IMPORTANT 2: This smoothing does not affect the stars in the image, it only has an effect on the background of the sky (nebulae and dark areas).

Two sliders are available to adjust the sky smoothing:

1. Radius: Adjusts the radius of the smoothing filter that is applied to the sky background (the larger the radius, the more smoothing is applied). A radius of 0 indicates that no smoothing is being applied.

1. Intensity: Adjusts the level of intensity with which smoothing is applied to the background of the sky. An intensity of 0 indicates no smoothing at all, while a value of 100 indicates maximum smoothing. The default value is 50.

Below are several example images of the results obtained using this tool:

Region (at 100% zoom) of an image of the galactic centre of the Milky Way captured in an area with very high light pollution, so the light pollution reduction had to be applied to the maximum (5 stops). Because of this, some noise has appeared in the background of the sky.

Same image as above, but applying a smoothing with a radius of 25 and an intensity of 50.

Same image applying a smoothing with a radius of 50 and an intensity of 50. In this case it can be seen that the nebulae in the galactic centre of the Milky Way are much more smoothed than in the original image, without the stars having any smoothing.

Smoothing with a radius of 50 (the same as in the previous image), but with a higher intensity level (75). Now the Milky Way nebulae are much more smoothed.

Smoothing with a radius of 50, but in this case the intensity level is lower (25), which is why this image shows a higher noise level than the previous ones.

And this is another example image using the "Smoothing" tool:

A region of an image of the galactic centre of the Milky Way in which some noise can be seen in the darker areas (due to the large light pollution reduction applied).

Same image as above, but in this case the nebulae at the galactic centre appear much softer as a radius of 80 with an intensity of 50 has been applied.

IMPORTANT: You can do all the tests you want by adjusting the radius and/or the smoothing intensity because these adjustments (like all Nebulb adjustments) are non-destructive, i.e. the image does not degrade at all no matter how many changes you make.

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