A method for determining baseline corrections in a spectrometer that measures the energy of events occurring in a detector connected to a preamplifier wherein the preamplifier produces pulses, referred to as event pulses, in response to events, wherein the spectrometer measures the energy of events by, using a first linear filter, referred to as the energy filter, to transform event pulses into shaped pulses (35, 42), referred to as energy pulses, wherein the energy pulses are characterized by a first basewidth, and wherein the energy filter's output signal is characterized by a DC offset (38, 48) in the absence of event pulses, the DC offset being referred to as the energy filter's baseline, measuring a characteristic of at least some energy pulses to provide estimates of the energies of their associated events, and using a baseline correction to compensate the measured characteristics for the energy filter's baseline; the method for determining such baseline corrections being characterized by: using a second linear filter, referred to as the baseline filter, to transform event pulses into shaped pulses, referred to as baseline pulses that are characterized by a second basewidth that is shorter than the first basewidth; determining times when the baseline filter is not processing any event pulses; capturing baseline values from the baseline filter during such determined times; and updating the baseline correction for the energy filter using at least some of the baseline values captured from the baseline filter. using a first linear filter, referred to as the energy filter, to transform event pulses into shaped pulses (35, 42), referred to as energy pulses, wherein the energy pulses are characterized by a first basewidth, and wherein the energy filter's output signal is characterized by a DC offset (38, 48) in the absence of event pulses, the DC offset being referred to as the energy filter's baseline, measuring a characteristic of at least some energy pulses to provide estimates of the energies of their associated events, and using a baseline correction to compensate the measured characteristics for the energy filter's baseline; the method for determining such baseline corrections being characterized by: using a second linear filter, referred to as the baseline filter, to transform event pulses into shaped pulses, referred to as baseline pulses that are characterized by a second basewidth that is shorter than the first basewidth; determining times when the baseline filter is not processing any event pulses; capturing baseline values from the baseline filter during such determined times; and updating the baseline correction for the energy filter using at least some of the baseline values captured from the baseline filter. using a second linear filter, referred to as the baseline filter, to transform event pulses into shaped pulses, referred to as baseline pulses that are characterized by a second basewidth that is shorter than the first basewidth; determining times when the baseline filter is not processing any event pulses; capturing baseline values from the baseline filter during such determined times; and updating the baseline correction for the energy filter using at least some of the baseline values captured from the baseline filter.