Hello Farzad_k,
I also don't think that DBE, or ABE, affects star selection.
Take into account that StarMask utility is strongly simplified by using a preliminar hard compression of dynamic range, following the suggestion of Juan Conejero, reported as anwer in the following post:
https://pixinsight.com/forum/index.php?topic=4559.0By using that method, the risk of selecting part of nebulae is actually negligible.
You can note the adoption of Contour option to select the stars' halos; however, specially in a first reducing step, could be better to select the stars entirely, before applying the Erosion (minimum) filter.
Sincerely,
Giuseppe.