Maskelyne's astronomical measurements were the first to be conducted.

But I must say that we're very proud of our own instrument, which has begun making important astronomical measurements.

Its principle was to lie at the heart of astronomical measurement down to the twentieth century.

The second thus defined is consistent with the ephemeris second, which was based on astronomical measurements.

So far, the comparisons point to a universe with a relatively low matter density, as other astronomical measurements have suggested.

"How in hell does an extraterrestrial know our system of astronomical measurements?"

They might guess, but they would never know, that it had once marked the zero point of all astronomical measurements.

It was a very large mural sextant that achieved a high level of accuracy for astronomical measurements.

The micrometer, as it became known, was to lie at the heart of astronomical measurement down to the twentieth century.