How to pronounce “1000th” in English

So it's like getting a new prescription of glasses that correct the distortions.But you have to do this very fast. The characteristic time in the atmosphere is about 1000th or a 2000th of a second on Mauna Kea.We so need to understand every 2000th of a second what aberrations have been introduced by the atmosphere. We then have to send signals to this deformable