Supernova ( SN ) 2018oh ( ASASSN-18bt ) is the first spectroscopically-confirmed type Ia supernova ( SN Ia ) observed in the Kepler field . The Kepler data revealed an excess emission in its early light curve , allowing to place interesting constraints on its progenitor system \citep dimitriadis-18oh , shappee-18oh . Here , we present extensive optical , ultraviolet , and near-infrared photometry , as well as dense sampling of optical spectra , for this object . SN 2018oh is relatively normal in its photometric evolution , with a rise time of 18.3 \pm 0.3 days and \Delta m _ { 15 } ( B ) = 0.96 \pm 0.03 mag , but it seems to have bluer B - V colors . We construct the “ uvoir ” bolometric light curve having peak luminosity as 1.49 \times 10 ^ { 43 } erg s ^ { -1 } , from which we derive a nickel mass as 0.55 \pm 0.04M _ { \odot } by fitting radiation diffusion models powered by centrally located ^ { 56 } Ni . Note that the moment when nickel-powered luminosity starts to emerge is +3.85 days after the first light in the Kepler data , suggesting other origins of the early-time emission , e.g. , mixing of ^ { 56 } Ni to outer layers of the ejecta or interaction between the ejecta and nearby circumstellar material or a non-degenerate companion star . The spectral evolution of SN 2018oh is similar to that of a normal SN Ia , but is characterized by prominent and persistent carbon absorption features . The C II features can be detected from the early phases to about 3 weeks after the maximum light , representing the latest detection of carbon ever recorded in a SN Ia . This indicates that a considerable amount of unburned carbon exists in the ejecta of SN 2018oh and may mix into deeper layers .