  Precision pulsar timing can be used for a variety of astrophysical tests from
the detection of gravitational waves to probing the properties of the
interstellar medium (ISM). Here we present analyses of the noise contributions
to pulsar timing residuals from continuous multi-hour observations of seven
millisecond pulsars (MSPs). We present scintillation bandwidth measurements for
all MSPs in the sample, some for the first time, and scintillation timescale
measurements and lower limits for all MSPs for the first time. In addition, we
present upper limits on the contribution of pulse phase jitter to the timing
residual error for all MSPs. These long observations also allow us to constrain
variations in dispersion measures (DMs) on hour-long timescales for several
millisecond pulsars. We find that there are no apparent DM variations in any of
the MSPs studied on these timescales as expected. In light of new radio
telescopes such as the Canadian Hydrogen Intensity Mapping Experiment (CHIME),
which will be able to time many pulsars for a short time each day, we search
for differences in timing precisions from continuous TOAs and from equivalent
length time-discontinuous TOAs. We find no differences in the precision for any
MSP in our sample, as expected. We conclude that the TOA variations are
consistent with the expected breakdown into template-fitting, jitter, and
scintillation errors.
