Operates using the same technology as the Mk. 1 Beer Goggles.
The beer monocular is used intermittently while surreptitiously draining your pint glass. The results are usually filtered at first through a coloured lens that will vary according to the beverage in your pint glass, ranging from very light - Carling Black Label, to practically impervious - Guinness. As the liquid diminishes the filter becomes less effective, until at last the beer monocular can be deployed in its unrestricted mode of operation.
Interestingly, the greater number of refills of the filter liquid and repeat observations, the greater the effectiveness of the beer monocular. The end result is exactly the same as the famed Beer Goggles.
Plans are underway to develop a model incorporating a night vision capability for use in low-light conditions (probably at the behest of THEM).
Here is an outstanding demonstration of a beer monocular actually being deployed in the field - Gulp-Lapse Photography