star trail
... that star trail observations of Polaris have been used to measure the vibrations in telescope mounting systems?
... that <b id="mwAVk"><a class="mw-redirect" href="./Star_trail_(photography)" id="mwAVo" rel="mw:WikiLink" title="Star trail (photography)">star trail</a></b> observations of <a href="./Polaris" id="mwAVs" rel="mw:WikiLink" title="Polaris">Polaris</a> <i id="mwAVw">(example pictured)</i> have been used to measure the vibrations in telescope mounting systems?