How can pirates work?

[rust]

My understanding was that a lot of the most recent discoveries by amatuers haven't so much been with their own equipment, but from analyzing available photos from various official sources, and then using their equipment to verify it.

Yep, a good example are a number of comets discovered by amateurs
using SOHO pictures.
Many professional projects, especially some of the satellites, produce
a lot more data than the professionals could evaluate themselves, so
these data are made available to amateurs.