That's a very interesting experiment Mirko; makes me want to try it for myself.
Upon searching for the Pixelteq bandpass filter, I stumbled upon an amazing image from one Tom Williams on Astrobin:
https://app.astrobin.com/equipment/e...10nm-fwhm-38nm
https://app.astrobin.com/i/psuedp
Apparently Tom used an additional IR850 filter because there was some green & blue light leaking past the Pixelteq. The extra filter may help a little in reducing the glare from the sunlit side.