diurnal parallax

If we know the value of the diurnal parallax, we can determine the distance to the Sun from the geometry of the Earth.

When the telescope became available, the diurnal parallax of Mars was again measured in an effort to determine the Sun-Earth distance.

Diurnal parallax is a parallax that varies with rotation of the Earth or with difference of location on the Earth.

For this purpose, the position of Mars was measured against the background stars from different points on the Earth, thereby measuring the diurnal parallax of the planet.

Since this new star displayed no detectable diurnal parallax, Galileo concluded that it was a distant star, and therefore disproved the Aristotelian belief in the immutability of the heavens.

During the seventeenth century, Tycho Brahe measured the diurnal parallax of Mars that Johannes Kepler used to make a preliminary calculation of the relative distance to the planet.

The diurnal parallax of the Sun was accurately measured during the transits of Venus in 1761 and 1769, yielding a value of 9" (compared to the present 1976 value of 8.794148").

The English astronomer David Gill used this opportunity to measure the diurnal parallax of Mars from Ascension Island, which led to a parallax estimate of 8.78 0.01 arcseconds.

The equations for horizontal coordinates do not account for diurnal parallax, that is, the small offset in the position of a celestial object caused by the position of the observer on the Earth's surface.