The Black Body & Extinction model is the default model
and is much more sophisticated than the Balance RGB model.
You will need to select areas with stars that are not strongly influenced by nebulosity.
The purpose is to select stars that represent main sequence stars. Realize that most of the stars in our images will be main sequence stars
that reside in our own galaxy, the Milky Way.
The model parameters, slope & constant, depend on the used camera
and the used filters, internally and/or externally
The constant parameters can be used to adjust for green/magenta cast.
If you need to lower/raise one of the constants lower/raise both constants a similar amount.
The Blue-Red slider needs to be used to perform the important white star calibration. Realize in this case, that most of the stars from the selected areas
will be red stars, since these live much longer than the blue stars. There are simply much more old red stars than young blue stars.
So most of the stars in your calibrated image, should normally be orange or red.
By adjusting the Blue-Red slider, you are informing APP the location
of white stars in the selected star population.
Adjust the slope values in such a way that the star populations in the
color-color diagrams nicely follow the model line.