Loaded images
This section shows the summary information of the total number of imported images. First is the number of imported images ("Count") and second is the total capture time between the first and last image ("Capture time").
IMPORTANT: The capture time is not the exposure time multiplied by the number of images, but it is the elapsed time between the first captured image and the last one. This is because for Nebulb what is important is the displacement of the stars in the sky (due to the Earth's rotation) during the time being captured, rather than the exposure time of each of the images.
First image
This section shows the name of the first image captured along with the date/time of capture.
Base image
This section shows the name and capture time of the image that Nebulb will use as the basis for the stacking, i.e. the image on which the stars of all the other images will be aligned during the stacking.
IMPORTANT: Nebulb automatically selects as the base image the one that is chronologically in the middle of the total capture interval, i.e. the base image is always the image that is captured right in the middle. Moreover, it is not possible to set the base image manually (change it for another one), since, for the best possible stacking result, it is convenient that the base image (on which the rest of the images are aligned) is the one captured in the center (so the stars are symmetrically displaced on both sides of the base image).
That said, once the stacking is finished, it is possible to select the exact time of the night for which to align the sky, which is especially useful for the processing of meteor showers (where it is important to align all the meteors according to the radiant for the time of the night that generates the greatest possible visual impact).
More information on the latter can be found in both the stacking (stacking refinement) and meteor shower processing documentation.
Last image
In this section the name of the last captured image is shown together with the date/time of capture.
Master image
This section shows the name and capture time of the master image (in case it has been imported).
It is very common to take a capture illuminating the scene, or taking advantage of the twilight at sunset or sunrise, and then merge it with the part of the sky obtained during stacking. Nebulb allows the import of a "master" image for this purpose.
Just as it is not possible to modify the base image on which the rest of the images are aligned, it is possible to select a master image for the ground, that is, in Nebulb you can obtain an image that is the result of merging the ground part of the master image with the sky obtained during stacking.