Nothing is more disappointing than when a newcomer to astrophotography sees those black frames for the first time.
It doesn’t matter whether it is from a One-Click, Advanced Request, or a Pro Data Set.
You will get the same thing. A zip file containing monochrome images, that when first opened in processing software presents the owner with nothing but black frames.
Don’t worry, it takes just a few times before it becomes second nature to stretch the frames.
Because there is so little light generated by the stars and deep space object, most of the pixels are occupied by the blackness of space. In order to see the image the user must use the Screen Transfer Function (STF). This basically allows the display of the lighter areas on the screen. It should be noted that this does not change the actual pixel values and the file is not saved a stretched version.
More information can be found at: https://pixinsight.com/.../ScreenTransferFunction.html...
But where’s the color?
The individual files produced during image acquisition each come from an exposure through an individual color filter. A grayscale image is produced of only that color light. When combined in the processing software the frames are assigned to individual layers representing Red, Blue, and Green and displayed in full color. In narrowband images, the same thing occurs, but the Ha,SII,OIII are mapped to the RGB colors as the user sees artistically fit.
During the processing stage there are many other steps that are used to improve the image, but this will keep you out of the darkness.