KELT-9b is a recently discovered exoplanet with a 1.49 d orbit around a B9.5/A0-type star . The unparalleled levels of UV irradiation it receives from its host star put KELT-9b in its own unique class of ultra-hot Jupiters , with an equilibrium temperature > 4000 K. The high quantities of dissociated hydrogen and atomic metals present in the dayside atmosphere of KELT-9b bear more resemblance to a K-type star than a gas giant . We present a single observation of KELT-9b during its secondary eclipse , taken with the Wide Field Camera on the Isaac Newton Telescope ( INT ) . This observation was taken in the U-band , a window particularly sensitive to Rayleigh scattering . We do not detect a secondary eclipse signal , but our 3 \sigma upper limit of 181 ppm on the depth allows us to constrain the dayside temperature of KELT-9b at pressures of \sim 30 mbar to 4995 K ( 3 \sigma ) . Although we can place an observational constraint of A _ { g } < 0.14 , our models suggest that the actual value is considerably lower than this due to \ce H- opacity . This places KELT-9b squarely in the albedo regime populated by its cooler cousins , almost all of which reflect very small components of the light incident on their daysides . This work demonstrates the ability of ground-based 2m-class telescopes like the INT to perform secondary eclipse studies in the NUV , which have previously only been conducted from space-based facilities .