The laser pointer is just so you get the bolometer or whatever other thermal chip they have in there in alignment w/ what you measure. So there is no "refraction" occuring because it is measuring the black body radiation emitted by the hot surface...
Night vision goggles work from about 900nm to 1200nm, advanced NVG's work up to 1400nm Humans start glowing in thermal imagers around 12000 to 14000 nm. Infra-red missile guidance on exhausts works in the 4000-8000 nm range...
So no problem on your flask..
Just went to the link...oooh i like that ALOT! guess I'll have to get one.. really good for checkning thermal loss on your fractionating column, oil bath temp. etc. May or may not work on measuring your flask contents, give the walls of the flask will be @ Oil bath temp. I tend to doubt that you could get an internal measurement w/ it. At least it goes up to 270 deg C which is the magic number!