With a -3dB point of 1.59 milliHerz, this is a filter for the ultra-low frequency band. It's only first-order, but I thought such a low-frequency filter with such ordinary components would be a little interesting, at least. The frequency can be set much lower by increasing the resistor alone.
Oh wait... it's dependent on the op-amp's exact gain. That is not good at all. :/ Op-amp gain varies with frequency, even in high-speed op-amps.
