Noisy voltage divider question
Following all the suggestions from Lundin, Frog and Lorenzo Marcantonio (in no particular order, thank you all for helping out), I took the following steps :

replaced the 1000uF capacitor with a 10uF one and added a 100nF one on the 5V side, but got interesting results :





Vcc
Vcc/2








A much noisier Vcc
A far more noisier Vcc/2





added a 100nF capacitor on the R2 which smoothed things out :



tried a different value for R1 and R2, buth lower and higher values, but there were no detectable changes, at least not with my DSO, which for some unknown reason refuses to chart a signal with lower tnan 0.2V/Div scale, so I cannot get a better 'image' of the signal.

My conclusion is that I need to keep the filtering capacitor on R2 and that most likely the DSO and wiring are responsible for some of the noise I see. I hope I can compensate for this later on.
Thank you all for helping out. Time to get to the next question for my project : Hall current sensor noise