The lifetime of the excited state of a material is essential for characterizing its photophysical and photochemical processes and substantially affects the quantum efficiencies of its luminescence (fluorescence or phosphorescence) and photo(catalytic) reactions. However, undergraduate students are much more likely to do steady-state, rather than time-resolved, spectroscopy in a laboratory class. In this report, a small hand-held photon-counting device is proposed for this measurement within a time scale from about 100 ns to 10 s. Measurements of emission decays from excited chromium(III) in ruby as a photophysical example and ruthenium(II) tris(bipyridine), [Ru(bpy)[subscript 3]][superscript 2+], as a photochemical example are demonstrated using the device.