  We report on spectroscopy of cold dysprosium atoms on the $1001\,\mathrm{nm}$
transition and present measurements of the excited state lifetime which is at
least $87.2(6.7)\,\mathrm{ms}$ long. Due to the long excited state lifetime we
are able to measure the ratio of the excited state polarizability to the ground
state polarizability at $1064\,\mathrm{nm}$ to be $0.828(0.129)$ by parametric
heating in an optical dipole trap. In addition we measure the isotope shifts of
the three most abundant bosonic isotopes of dysprosium on the
$1001\,\mathrm{nm}$ transition with an accuracy better than $30\,\mathrm{kHz}$.
