On improving IR photometric passbands

In response to recommendations made by a Working Group on Infrared Extinction and Standardisation of IAU Commission 25, we have compared the past and present versions of the passbands in the Johnson JHKLMNQ broadband photometric system used at a number of observatories with the atmospheric window transmissions calculated by MODTRAN. The existing passbands are very diverse; contrary to a widespread misperception, there is no semblance of a standard set in use. We have used a family of solar-composition model stellar fluxes from Kurucz (1991 private communication) to model the atmospheric extinction under different water-vapor, height, and airmass conditions. Thus, we have simulated extinction curves for the infrared passbands used at several observatories