John created a new topic ' Darks, Flats and bias frames' in the forum. 9 months ago

As I have become a bit more comfortable with my asrtoberry setup and using kstars/ekos I would like to start taking additional frames to hopefully help with my stacking.  I was already taking dark frames, but I guess I want to check if I am doing all this right.

For dark frames I cover my scope and take 20 or so frames at the same conditions as the subs  I took.  I then drop all of those frames into DSS with my light subs and stack.
Flats confuse me still.  I covered my telescope with some white cloth and tried to get even lighting (have a light on the way) and used the calibration wizard or whatever in ekos.  I just selected Flats > dust cap with light > and then number of frames I wanted.
I am lost on the difference between bias and darks.

So my questions are what are bias frames and how do you take them? For flats do I need to do any post processing or does it work just like darks and I throw them all into dss for it to make a master flat file (do I need to do any histogram editing or anything first)?  I want to figure this out because the biggest issue I have with my pictures now is vignetting and then gradient circle stemming out from the center ( I assume this may be light pollution).