Hi Alec,
thank you for your reply. The first schematic will not work. The second works well for what it needs to do: detect light variation at low intervals (>1 second, up to minutes).
I made a new schematic, this time to compare the second circuit above with a design needing only one comparator.
I am in a bind however how to introduce a delay for the voltage on pin 9 (non-inverting) going up on the one-comparator design.
Downward voltage may be immediate; upward I would like to see an RC delay.
I have a gut feeling this will need an active component (mosfet)?