Exclude images with stray lights during star trails stacking
One of the main problems that star trails images have always had is that, as they are obtained by maximum stacking, any light that appears during the whole capture time is added to the final image (whether it is in the sky or on the ground).
To solve the problem of stray lights in the sky (by planes, satellites or meteors) Nebulb has a functionality that allows to automatically remove all those unwanted light trails and leave only those of the stars (https://help.nebulb.com/portal/en/kb/articles/remove-flying-objects-in-star-trails).
However, in many occasions the problem of stray lights also occurs on the ground, since it is quite common that the lights of a vehicle or the headlights of a person end up illuminating the scene in an unwanted way.
To avoid this problem, what used to be done was to review, one by one, all the images to remove those in which there was a stray light. However, this had two drawbacks:
1. One had to do a manual review job of all the images (which is a somewhat tedious task).2. Removing images that had stray lights generated gaps in the star trails (which is far from desirable).
Well, precisely to solve this problem (without generating these two inconveniences) Nebulb has the option "Exclude images with stray lights".
By selecting this option Nebulb analyzes the light intensity of the scene (the part of the ground) in all images and automatically excludes from the stack those that have some stray light, so that these lights do not appear in the final image. In addition, the exclusion of images with stray lights does not generate any gaps in the star trails, since Nebulb has a mechanism to fill the possible gaps that appear in the star trails (https://help.nebulb.com/portal/en/kb/articles/smooth-and-fill-star-trails).
Below you can see how by activating the option "Exclude images with stray lights" the lights of a car that were turned on during the capture do not appear in the final image:
IMPORTANT: The "Exclude images with stray lights" option is disabled by default, since enabling it also discards all images that have been voluntarily illuminated (Nebulb cannot differentiate between voluntary and unwanted lights). So do not activate this option in case you have specifically illuminated one of the images and do not want it to be discarded (although you could also import it as a master image, as explained here: https://help.nebulb.com/portal/en/kb/articles/import-a-master-image-for-the-ground). However, if this is not the case and you know that there were stray lights during the capture, you can activate this option so that Nebulb automatically discards them.