I am helping out on a project from the Lowell Observatory on young M class dwarf stars, trying to determine the rotational period of a number of selected objects. The assumption is these stars have large spots, which makes detection of a rotation period possible. Being M class objects, they are of course very red, as is several (of the very few) available comp stars in the various fields.
I know there is a general prohibition about using reddish comp stars, but how about for for red stars themselves? I am thinking since I don't need a precise corrected magnitude, only a differential magnitude to measure the light changes, it shouldn't make all that much difference.