The Orange Tip (Anthocharis cardamines) is a common butterfly (that counts at least up here in Finland) and finding eggs is not too difficult. However, as with any species, the time and place must be right.
The shape of the eggs is pretty similar to those of the Common Brimstone (Gonepteryx rhamni). Eggs will be around only for a short period as the caterpillars tend to hatch already after 5-7 days. Once you start seeing the first males flying, wait for another moment. I waited two weeks this spring after spotting the first male, and got lucky. The first female I actually sighted after first finding the first eggs.
Here’s a couple photos from my search this spring. I also tried to capture the larval habitat to show what kind of surrounding I found eggs in.
