A portion of the UV SED of 3C 454.3 as seen by GALEX in 2008 October (in black). The red SED points are derived from a contemporary UVOT observation. At z = 0.859, the Lyα line (λ₀ = 1216Å) is shifted close to the effective frequency of the uvm2 filter, while the neighbouring uvw2 and uvw1 are less sensitive to it. The observer-frame frequency of the Lyα line is shown by the dotted vertical line. The effective areas of the UVOT filters are also plotted for reference, with thick dotted lines; the reference scale is reported on the right vertical axis.