They had thirteen offspring, of which four sons survived to adulthood:[5] In addition to his astronomical interests, Rosse served as a Member of Parliament (MP) for King's County from 1821 to 1834, president of the British Association in 1843–1844,[6] an Irish representative peer after 1845, president of the Royal Society (1848–1854), and chancellor of the University of Dublin (Trinity College Dublin) (1862–1867).

He was appointed Colonel of the disembodied King's County Royal Rifle Militia (a regiment formerly commanded by his father) from 19 June 1834 and was joined by his younger brother the Hon Lawrence Parsons as Lieutenant-Colonel from 24 December 1847.

He had to invent many of the techniques he used for constructing the Leviathan, both because its size was without precedent and because earlier telescope builders had guarded their secrets or had not published their methods.

[8] Rosse's telescope was considered a marvellous technical and architectural achievement, and images of it were circulated widely within the British Commonwealth.

A few years later, when the 72-inch (183 cm) telescope was in service, he (or one of his assistants) produced an improved drawing of a considerably different appearance, but the original name continued to be used.

In 1845 Rosse and his technicians claimed to have resolved the Orion nebula into its individual stars using the Leviathan, a claim which had considerable cosmological and even philosophical implications, as at the time there was considerable debate over whether or not the universe was "evolved" (in a pre-Darwinian sense), a concept which the nebular hypothesis supported and with which Rosse disagreed strongly.

One of Rosse's telescope admirers was Thomas Langlois Lefroy, a fellow Irish MP, who said, "The planet Jupiter, which through an ordinary glass is no larger than a good star, is seen twice as large as the moon appears to the naked eye...