The business end, the rectangle is the sensor. There is a window in front of it,
I DO NOT know if it is a UV/IR blocking filter. When I'm not using any other kind of filter
I keep a UV/IR filter in place. In the past it was somewhat customary to use a UV/IR
blocking window on color CMOS cameras in general, but it has become less common
with the wide use of dual/tri band filters, reason being the IR blocking diminishes
the Ha signal. I recommend the use of a UV/IR blocker, even if you never intend
to get any other filters. They're cheap and any dust that gets in the tube will
be kept farther away from the sensor, minimizing the possibility of dust bunnies in your images.