Can I install a photocell on a 3-way switched circuit?
Yes.

The photocell is placed in series with the feed from the panel ahead of the switches. The white is the neutral, the black is the hot feed, and the red is the switched hot. Of course, this makes the circuit inoperable during the light of day and there will be no manual override.

I would install an astronomical timer like this one:
https://www.amazon.com/gp/product/B004AP92N2/ref=oh_aui_search_detailpage?ie=UTF8&amp;psc=1

This also goes in series with the switches in the circuit but it has a manual override and does not need to be placed outdoors. The built-in computer calculates the times for dawn and dusk for your lattitude and longitude. Those default start and stop times can be adjusted to your preferences.

Good luck and stay safe!