For an upcoming project I bought an ASI294. See some properties of my first CMOS detector. Here about Bias and Dark,Flatfield
A black body surrounded by a gaseous atmosphere gives a spectrum with continuum and absorption lines. See here.
The rotation of a planet is giving itself in the tilted absorption lines of the reflected sunlight. It is easy to measure with a long slit spektrograph. Find an article about the rotation of Jupiter in German here.