Plastic lenses for LWIR?

[Ultrapurple]

Here is (more or less) the setup I used for the initial Fresnel lens experiments.

The photos were taken the day after, so aren't a 100% accurate representation of what I did; in particular, the 25mm FL length Fresnel lens shown was much closer to the Therm-App imager for focus, and I  didn't bother to ensure the lens was perfectly aligned (height, L/R, square-on to the imager, etc).