Abstract: Careful and accurate indication of regeneration temperatures of catalysts associated with the refining of hydrocarbons such as occurring in catalyst-aided hydrocracking and catalyst-aided reforming processes--in real time--occurs by monitoring--from an overflying aircraft--the infrared energy, say in a frequency range greater than 300 .times. 10.sup.9 but not more than 10.sup.15 Hertz, emitted from a plurality of distributed metallic studs mounted as by welding to the exterior surface of the sidewall of a vessel undergoing catalytic regeneration. The dynamic temperature variation of such energy rays readily indicates regeneration temperatures of the catalyst interior of the vessel. The studs extend through the insulation of the vessel but do not penetrate its interior. Where the regeneration process is cyclically occurring, not only is there a marked decrease in the time required for regeneration, but there is also better statistical certainty that full regeneration of the catalyst has occurred.