As per the title.
I've got a Pulsar Apex XD50 thermal riflescope to use for a while -- and am racking what little brain I seem to have left to devise a good zeroing target.
Black shoot-n-see roundels on a white backer seemed like a good idea, but only as long as the sun was on the target face: as soon as the sun went in the heat differential -and the roundels- disappeared.
So I really want something that (1) holds its thermal signature independent of its surroundings, (2) is large enough to see at 100m (3) is small enough to allow a precise point of aim, (4) bears a sufficiently constant relation to a backer so that misses can be seen and corrected for easily and accurately, (5) is readily available, (6) is easily portable, and (7, 8 9 & 10) is cheap!
At the moment I'm thinking of filling some old 12g cartridges with water, freezing them, taking them into the field in a Thermos, and poking them into pre-prepared holes in a cardboard backer...
But then I have been at the whiskey!
As ever, all helpful suggestions will be much appreciated, and I await the wisdom and wit of the SD with eager anticipation!