Crabtree was born in 1610 in the hamlet of Broughton Spout, which was on the east bank of the River Irwell, near the area now known as "The Priory" in Broughton, Salford and was educated at the Manchester Grammar School.
He married into a wealthy family and worked as a merchant in Manchester.
In his spare time, his great interest was astronomy.
He carefully measured the movements of the planets and undertook precise astronomical calculations.
With improved accuracy, he rewrote the existing Rudolphine Tables of Planetary Positions.

Crabtree corresponded with Jeremiah Horrocks, another enthusiastic amateur astronomer, from 1636.
A group of astronomers from the north of England, which included William Gascoigne, formed around them and were Britain's first followers of the astronomy of Johannes Kepler. "
Nos Keplari" as the group called themselves, were distinguished as being the first people to gain a realistic notion of the size of the solar system.
Crabtree and Horrocks were the only astronomers to observe, plot, and record the transit of Venus across the Sun, as predicted by Horrocks, on 24 November 1639 Julian calendar (4 December Gregorian calendar).
The two correspondents both recorded the event in their own homes and it is not known whether they ever met in person, but Crabtree's calculations were crucial in allowing Horrocks to estimate the size of Venus and the distance from the Earth to the Sun.
Unfortunately, Horrocks died early in 1641 – the day before he was due to meet Crabtree.
Crabtree made his will on 19 July 1644, and was buried within the precincts of the Manchester Collegiate Church on 1 August 1644, close to where he had received his education.

The recording of the transit is now seen by many as the birth of modern astronomy in Britain, and indeed, John Flamsteed later said that the work of Horrocks and his north country colleagues laid much of the foundation upon which his work as Astronomer Royal would stand.
Crabtree was born in 1610 in the hamlet of Broughton Spout, which was on the east bank of the River Irwell, near the area now known as "The Priory" in Broughton, Salford and was educated at the Manchester Grammar School. He married into a wealthy family and worked as a merchant in Manchester. In his spare time, his great interest was astronomy. He carefully measured the movements of the planets and undertook precise astronomical calculations. With improved accuracy, he rewrote the existing Rudolphine Tables of Planetary Positions.
Crabtree corresponded with Jeremiah Horrocks, another enthusiastic amateur astronomer, from 1636. A group of astronomers from the north of England, which included William Gascoigne, formed around them and were Britain's first followers of the astronomy of Johannes Kepler. "Nos Keplari" as the group called themselves, were distinguished as being the first people to gain a realistic notion of the size of the solar system. Crabtree and Horrocks were the only astronomers to observe, plot, and record the transit of Venus across the Sun, as predicted by Horrocks, on 24 November 1639 Julian calendar (4 December Gregorian calendar). The two correspondents both recorded the event in their own homes and it is not known whether they ever met in person, but Crabtree's calculations were crucial in allowing Horrocks to estimate the size of Venus and the distance from the Earth to the Sun. Unfortunately, Horrocks died early in 1641 – the day before he was due to meet Crabtree. Crabtree made his will on 19 July 1644, and was buried within the precincts of the Manchester Collegiate Church on 1 August 1644, close to where he had received his education.
The recording of the transit is now seen by many as the birth of modern astronomy in Britain, and indeed, John Flamsteed later said that the work of Horrocks and his north country colleagues laid much of the foundation upon which his work as Astronomer Royal would stand.
William Crabtree