I understand that stacking multiple exposures and using calibration frame will produce better final results than leaving out any one of those ingredients, but my question is this: If I don't have, for example, flat frames, will my stacked images suffer more than if I had taken a single exposure?
The reason I ask is that I attempted my first imaging session with multiple exposures and calibration frames two nights ago. Unfortunately, I messed up the flat frames by finding out too late that I should have retained my focus setting and camera orientation. I attempted to reproduce them from memory, but that was unlikely correct, and my results weren't very appealing - lots of vignetting.
I then decided to try stacking without the flat frames, guessing that they were doing more harm than good and assuming that my results would be at least better than a single exposure with no calibration at all. I was surprised to find that I still had noticeable vignetting, which I had not seen the week before with a single exposure.
Is there anything about the stacking process that exaggerates whatever vignetting might be occurring?