Does jackknife scale really matter for accurate large-scale structure
  covariances?
  The jackknife method gives an internal covariance estimate for large-scale
structure surveys and allows model-independent errors on cosmological
parameters. Using the SDSS-III BOSS CMASS sample, we study how the jackknife
size and number of resamplings impact the precision of the covariance estimate
on the correlation function multipoles and the error on the inferred baryon
acoustic scale. We compare the measurement with the MultiDark Patchy mock
galaxy catalogues, and we also validate it against a set of log-normal mocks
with the same survey geometry. We build several jackknife configurations that
vary in size and number of resamplings. We introduce the Hartlap factor in the
covariance estimate that depends on the number of jackknife resamplings. We
also find that it is useful to apply the tapering scheme to estimate the
precision matrix from a limited number of resamplings. The results from CMASS
and mock catalogues show that the error estimate of the baryon acoustic scale
does not depend on the jackknife scale. For the shift parameter $\alpha$, we
find an average error of 1.6%, 2.2% and 1.2%, respectively from CMASS, Patchy
and log-normal jackknife covariances. Despite these uncertainties fluctuate
significantly due to some structural limitations of the jackknife method, our
$\alpha$ estimates are in reasonable agreement with published
pre-reconstruction analyses. Jackknife methods will provide valuable and
complementary covariance estimates for future large-scale structure surveys.
